text: // Copyright 2015 The Chromium Authors. All rights reserved.
  // Use of this source code is governed by a BSD-style license that can be
  // found in the LICENSE file.
  
  #include "media/gpu/v4l2_slice_video_decode_accelerator.h"
  
  #include <errno.h>
  #include <fcntl.h>
  #include <linux/videodev2.h>
  #include <poll.h>
  #include <string.h>
  #include <sys/eventfd.h>
  #include <sys/ioctl.h>
  #include <sys/mman.h>
  
  #include <memory>
  
  #include "base/bind.h"
  #include "base/bind_helpers.h"
  #include "base/callback.h"
  #include "base/callback_helpers.h"
  #include "base/command_line.h"
  #include "base/macros.h"
  #include "base/memory/ptr_util.h"
  #include "base/numerics/safe_conversions.h"
  #include "base/strings/stringprintf.h"
  #include "media/base/bind_to_current_loop.h"
  #include "media/base/media_switches.h"
  #include "media/gpu/shared_memory_region.h"
  #include "ui/gl/gl_context.h"
  #include "ui/gl/scoped_binders.h"
  
  #define LOGF(level) LOG(level) << __FUNCTION__ << "(): "
  #define DVLOGF(level) DVLOG(level) << __FUNCTION__ << "(): "
  
  #define NOTIFY_ERROR(x)                        \
    do {                                         \
      LOG(ERROR) << "Setting error state:" << x; \
      SetErrorState(x);                          \
    } while (0)
  
  #define IOCTL_OR_ERROR_RETURN_VALUE(type, arg, value, type_str)          \
    do {                                                                   \
      if (device_->Ioctl(type, arg) != 0) {                                \
        PLOG(ERROR) << __FUNCTION__ << "(): ioctl() failed: " << type_str; \
        return value;                                                      \
      }                                                                    \
    } while (0)
  
  #define IOCTL_OR_ERROR_RETURN(type, arg) \
    IOCTL_OR_ERROR_RETURN_VALUE(type, arg, ((void)0), #type)
  
  #define IOCTL_OR_ERROR_RETURN_FALSE(type, arg) \
    IOCTL_OR_ERROR_RETURN_VALUE(type, arg, false, #type)
  
  #define IOCTL_OR_LOG_ERROR(type, arg)                                 \
    do {                                                                \
      if (device_->Ioctl(type, arg) != 0)                               \
        PLOG(ERROR) << __FUNCTION__ << "(): ioctl() failed: " << #type; \
    } while (0)
  
  namespace media {
  
  // static
  const uint32_t V4L2SliceVideoDecodeAccelerator::supported_input_fourccs_[] = {
      V4L2_PIX_FMT_H264_SLICE, V4L2_PIX_FMT_VP8_FRAME,
  };
  
  class V4L2SliceVideoDecodeAccelerator::V4L2DecodeSurface
      : public base::RefCounted<V4L2DecodeSurface> {
   public:
    using ReleaseCB = base::Callback<void(int)>;
  
    V4L2DecodeSurface(int32_t bitstream_id,
                      int input_record,
                      int output_record,
                      const ReleaseCB& release_cb);
  
    // Mark the surface as decoded. This will also release all references, as
    // they are not needed anymore.
    void SetDecoded();
    bool decoded() const { return decoded_; }
  
    int32_t bitstream_id() const { return bitstream_id_; }
    int input_record() const { return input_record_; }
    int output_record() const { return output_record_; }
    uint32_t config_store() const { return config_store_; }
  
    // Take references to each reference surface and keep them until the
    // target surface is decoded.
    void SetReferenceSurfaces(
        const std::vector<scoped_refptr<V4L2DecodeSurface>>& ref_surfaces);
  
    std::string ToString() const;
  
   private:
    friend class base::RefCounted<V4L2DecodeSurface>;
    ~V4L2DecodeSurface();
  
    int32_t bitstream_id_;
    int input_record_;
    int output_record_;
    uint32_t config_store_;
  
    bool decoded_;
    ReleaseCB release_cb_;
  
    std::vector<scoped_refptr<V4L2DecodeSurface>> reference_surfaces_;
  
    DISALLOW_COPY_AND_ASSIGN(V4L2DecodeSurface);
  };
  
  V4L2SliceVideoDecodeAccelerator::V4L2DecodeSurface::V4L2DecodeSurface(
      int32_t bitstream_id,
      int input_record,
      int output_record,
      const ReleaseCB& release_cb)
      : bitstream_id_(bitstream_id),
        input_record_(input_record),
        output_record_(output_record),
        config_store_(input_record + 1),
        decoded_(false),
        release_cb_(release_cb) {}
  
  V4L2SliceVideoDecodeAccelerator::V4L2DecodeSurface::~V4L2DecodeSurface() {
    DVLOGF(5) << "Releasing output record id=" << output_record_;
    release_cb_.Run(output_record_);
  }
  
  void V4L2SliceVideoDecodeAccelerator::V4L2DecodeSurface::SetReferenceSurfaces(
      const std::vector<scoped_refptr<V4L2DecodeSurface>>& ref_surfaces) {
    DCHECK(reference_surfaces_.empty());
    reference_surfaces_ = ref_surfaces;
  }
  
  void V4L2SliceVideoDecodeAccelerator::V4L2DecodeSurface::SetDecoded() {
    DCHECK(!decoded_);
    decoded_ = true;
  
    // We can now drop references to all reference surfaces for this surface
    // as we are done with decoding.
    reference_surfaces_.clear();
  }
  
  std::string V4L2SliceVideoDecodeAccelerator::V4L2DecodeSurface::ToString()
      const {
    std::string out;
    base::StringAppendF(&out, "Buffer %d -> %d. ", input_record_, output_record_);
    base::StringAppendF(&out, "Reference surfaces:");
    for (const auto& ref : reference_surfaces_) {
      DCHECK_NE(ref->output_record(), output_record_);
      base::StringAppendF(&out, " %d", ref->output_record());
    }
    return out;
  }
  
  V4L2SliceVideoDecodeAccelerator::InputRecord::InputRecord()
      : input_id(-1),
        address(nullptr),
        length(0),
        bytes_used(0),
        at_device(false) {}
  
  V4L2SliceVideoDecodeAccelerator::OutputRecord::OutputRecord()
      : at_device(false),
        at_client(false),
        picture_id(-1),
        texture_id(0),
        egl_image(EGL_NO_IMAGE_KHR),
        egl_sync(EGL_NO_SYNC_KHR),
        cleared(false) {}
  
  struct V4L2SliceVideoDecodeAccelerator::BitstreamBufferRef {
    BitstreamBufferRef(
        base::WeakPtr<VideoDecodeAccelerator::Client>& client,
        const scoped_refptr<base::SingleThreadTaskRunner>& client_task_runner,
        SharedMemoryRegion* shm,
        int32_t input_id);
    ~BitstreamBufferRef();
    const base::WeakPtr<VideoDecodeAccelerator::Client> client;
    const scoped_refptr<base::SingleThreadTaskRunner> client_task_runner;
    const std::unique_ptr<SharedMemoryRegion> shm;
    off_t bytes_used;
    const int32_t input_id;
  };
  
  V4L2SliceVideoDecodeAccelerator::BitstreamBufferRef::BitstreamBufferRef(
      base::WeakPtr<VideoDecodeAccelerator::Client>& client,
      const scoped_refptr<base::SingleThreadTaskRunner>& client_task_runner,
      SharedMemoryRegion* shm,
      int32_t input_id)
      : client(client),
        client_task_runner(client_task_runner),
        shm(shm),
        bytes_used(0),
        input_id(input_id) {}
  
  V4L2SliceVideoDecodeAccelerator::BitstreamBufferRef::~BitstreamBufferRef() {
    if (input_id >= 0) {
      DVLOGF(5) << "returning input_id: " << input_id;
      client_task_runner->PostTask(
          FROM_HERE,
          base::Bind(&VideoDecodeAccelerator::Client::NotifyEndOfBitstreamBuffer,
                     client, input_id));
    }
  }
  
  struct V4L2SliceVideoDecodeAccelerator::EGLSyncKHRRef {
    EGLSyncKHRRef(EGLDisplay egl_display, EGLSyncKHR egl_sync);
    ~EGLSyncKHRRef();
    EGLDisplay const egl_display;
    EGLSyncKHR egl_sync;
  };
  
  V4L2SliceVideoDecodeAccelerator::EGLSyncKHRRef::EGLSyncKHRRef(
      EGLDisplay egl_display,
      EGLSyncKHR egl_sync)
      : egl_display(egl_display), egl_sync(egl_sync) {}
  
  V4L2SliceVideoDecodeAccelerator::EGLSyncKHRRef::~EGLSyncKHRRef() {
    // We don't check for eglDestroySyncKHR failures, because if we get here
    // with a valid sync object, something went wrong and we are getting
    // destroyed anyway.
    if (egl_sync != EGL_NO_SYNC_KHR)
      eglDestroySyncKHR(egl_display, egl_sync);
  }
  
  struct V4L2SliceVideoDecodeAccelerator::PictureRecord {
    PictureRecord(bool cleared, const media::Picture& picture);
    ~PictureRecord();
    bool cleared;  // Whether the texture is cleared and safe to render from.
    media::Picture picture;  // The decoded picture.
  };
  
  V4L2SliceVideoDecodeAccelerator::PictureRecord::PictureRecord(
      bool cleared,
      const media::Picture& picture)
      : cleared(cleared), picture(picture) {}
  
  V4L2SliceVideoDecodeAccelerator::PictureRecord::~PictureRecord() {}
  
  class V4L2SliceVideoDecodeAccelerator::V4L2H264Accelerator
      : public H264Decoder::H264Accelerator {
   public:
    V4L2H264Accelerator(V4L2SliceVideoDecodeAccelerator* v4l2_dec);
    ~V4L2H264Accelerator() override;
  
    // H264Decoder::H264Accelerator implementation.
    scoped_refptr<H264Picture> CreateH264Picture() override;
  
    bool SubmitFrameMetadata(const media::H264SPS* sps,
                             const media::H264PPS* pps,
                             const H264DPB& dpb,
                             const H264Picture::Vector& ref_pic_listp0,
                             const H264Picture::Vector& ref_pic_listb0,
                             const H264Picture::Vector& ref_pic_listb1,
                             const scoped_refptr<H264Picture>& pic) override;
  
    bool SubmitSlice(const media::H264PPS* pps,
                     const media::H264SliceHeader* slice_hdr,
                     const H264Picture::Vector& ref_pic_list0,
                     const H264Picture::Vector& ref_pic_list1,
                     const scoped_refptr<H264Picture>& pic,
                     const uint8_t* data,
                     size_t size) override;
  
    bool SubmitDecode(const scoped_refptr<H264Picture>& pic) override;
    bool OutputPicture(const scoped_refptr<H264Picture>& pic) override;
  
    void Reset() override;
  
   private:
    // Max size of reference list.
    static const size_t kDPBIndicesListSize = 32;
    void H264PictureListToDPBIndicesList(const H264Picture::Vector& src_pic_list,
                                         uint8_t dst_list[kDPBIndicesListSize]);
  
    void H264DPBToV4L2DPB(
        const H264DPB& dpb,
        std::vector<scoped_refptr<V4L2DecodeSurface>>* ref_surfaces);
  
    scoped_refptr<V4L2DecodeSurface> H264PictureToV4L2DecodeSurface(
        const scoped_refptr<H264Picture>& pic);
  
    size_t num_slices_;
    V4L2SliceVideoDecodeAccelerator* v4l2_dec_;
  
    // TODO(posciak): This should be queried from hardware once supported.
    static const size_t kMaxSlices = 16;
    struct v4l2_ctrl_h264_slice_param v4l2_slice_params_[kMaxSlices];
    struct v4l2_ctrl_h264_decode_param v4l2_decode_param_;
  
    DISALLOW_COPY_AND_ASSIGN(V4L2H264Accelerator);
  };
  
  class V4L2SliceVideoDecodeAccelerator::V4L2VP8Accelerator
      : public VP8Decoder::VP8Accelerator {
   public:
    V4L2VP8Accelerator(V4L2SliceVideoDecodeAccelerator* v4l2_dec);
    ~V4L2VP8Accelerator() override;
  
    // VP8Decoder::VP8Accelerator implementation.
    scoped_refptr<VP8Picture> CreateVP8Picture() override;
  
    bool SubmitDecode(const scoped_refptr<VP8Picture>& pic,
                      const media::Vp8FrameHeader* frame_hdr,
                      const scoped_refptr<VP8Picture>& last_frame,
                      const scoped_refptr<VP8Picture>& golden_frame,
                      const scoped_refptr<VP8Picture>& alt_frame) override;
  
    bool OutputPicture(const scoped_refptr<VP8Picture>& pic) override;
  
   private:
    scoped_refptr<V4L2DecodeSurface> VP8PictureToV4L2DecodeSurface(
        const scoped_refptr<VP8Picture>& pic);
  
    V4L2SliceVideoDecodeAccelerator* v4l2_dec_;
  
    DISALLOW_COPY_AND_ASSIGN(V4L2VP8Accelerator);
  };
  
  // Codec-specific subclasses of software decoder picture classes.
  // This allows us to keep decoders oblivious of our implementation details.
  class V4L2H264Picture : public H264Picture {
   public:
    V4L2H264Picture(
        const scoped_refptr<V4L2SliceVideoDecodeAccelerator::V4L2DecodeSurface>&
            dec_surface);
  
    V4L2H264Picture* AsV4L2H264Picture() override { return this; }
    scoped_refptr<V4L2SliceVideoDecodeAccelerator::V4L2DecodeSurface>
    dec_surface() {
      return dec_surface_;
    }
  
   private:
    ~V4L2H264Picture() override;
  
    scoped_refptr<V4L2SliceVideoDecodeAccelerator::V4L2DecodeSurface>
        dec_surface_;
  
    DISALLOW_COPY_AND_ASSIGN(V4L2H264Picture);
  };
  
  V4L2H264Picture::V4L2H264Picture(
      const scoped_refptr<V4L2SliceVideoDecodeAccelerator::V4L2DecodeSurface>&
          dec_surface)
      : dec_surface_(dec_surface) {}
  
  V4L2H264Picture::~V4L2H264Picture() {}
  
  class V4L2VP8Picture : public VP8Picture {
   public:
    V4L2VP8Picture(
        const scoped_refptr<V4L2SliceVideoDecodeAccelerator::V4L2DecodeSurface>&
            dec_surface);
  
    V4L2VP8Picture* AsV4L2VP8Picture() override { return this; }
    scoped_refptr<V4L2SliceVideoDecodeAccelerator::V4L2DecodeSurface>
    dec_surface() {
      return dec_surface_;
    }
  
   private:
    ~V4L2VP8Picture() override;
  
    scoped_refptr<V4L2SliceVideoDecodeAccelerator::V4L2DecodeSurface>
        dec_surface_;
  
    DISALLOW_COPY_AND_ASSIGN(V4L2VP8Picture);
  };
  
  V4L2VP8Picture::V4L2VP8Picture(
      const scoped_refptr<V4L2SliceVideoDecodeAccelerator::V4L2DecodeSurface>&
          dec_surface)
      : dec_surface_(dec_surface) {}
  
  V4L2VP8Picture::~V4L2VP8Picture() {}
  
  V4L2SliceVideoDecodeAccelerator::V4L2SliceVideoDecodeAccelerator(
      const scoped_refptr<V4L2Device>& device,
      EGLDisplay egl_display,
      const GetGLContextCallback& get_gl_context_cb,
      const MakeGLContextCurrentCallback& make_context_current_cb)
      : input_planes_count_(0),
        output_planes_count_(0),
        child_task_runner_(base::ThreadTaskRunnerHandle::Get()),
        device_(device),
        decoder_thread_("V4L2SliceVideoDecodeAcceleratorThread"),
        device_poll_thread_("V4L2SliceVideoDecodeAcceleratorDevicePollThread"),
        input_streamon_(false),
        input_buffer_queued_count_(0),
        output_streamon_(false),
        output_buffer_queued_count_(0),
        video_profile_(media::VIDEO_CODEC_PROFILE_UNKNOWN),
        output_format_fourcc_(0),
        state_(kUninitialized),
        output_mode_(Config::OutputMode::ALLOCATE),
        decoder_flushing_(false),
        decoder_resetting_(false),
        surface_set_change_pending_(false),
        picture_clearing_count_(0),
        egl_display_(egl_display),
        get_gl_context_cb_(get_gl_context_cb),
        make_context_current_cb_(make_context_current_cb),
        weak_this_factory_(this) {
    weak_this_ = weak_this_factory_.GetWeakPtr();
  }
  
  V4L2SliceVideoDecodeAccelerator::~V4L2SliceVideoDecodeAccelerator() {
    DVLOGF(2);
  
    DCHECK(child_task_runner_->BelongsToCurrentThread());
    DCHECK(!decoder_thread_.IsRunning());
    DCHECK(!device_poll_thread_.IsRunning());
  
    DCHECK(input_buffer_map_.empty());
    DCHECK(output_buffer_map_.empty());
  }
  
  void V4L2SliceVideoDecodeAccelerator::NotifyError(Error error) {
    if (!child_task_runner_->BelongsToCurrentThread()) {
      child_task_runner_->PostTask(
          FROM_HERE, base::Bind(&V4L2SliceVideoDecodeAccelerator::NotifyError,
                                weak_this_, error));
      return;
    }
  
    if (client_) {
      client_->NotifyError(error);
      client_ptr_factory_.reset();
    }
  }
  
  bool V4L2SliceVideoDecodeAccelerator::Initialize(const Config& config,
                                                   Client* client) {
    DVLOGF(3) << "profile: " << config.profile;
    DCHECK(child_task_runner_->BelongsToCurrentThread());
    DCHECK_EQ(state_, kUninitialized);
  
    if (!device_->SupportsDecodeProfileForV4L2PixelFormats(
            config.profile, arraysize(supported_input_fourccs_),
            supported_input_fourccs_)) {
      DVLOGF(1) << "unsupported profile " << config.profile;
      return false;
    }
  
    if (config.is_encrypted) {
      NOTREACHED() << "Encrypted streams are not supported for this VDA";
      return false;
    }
  
    if (config.output_mode != Config::OutputMode::ALLOCATE &&
        config.output_mode != Config::OutputMode::IMPORT) {
      NOTREACHED() << "Only ALLOCATE and IMPORT OutputModes are supported";
      return false;
    }
  
    client_ptr_factory_.reset(
        new base::WeakPtrFactory<VideoDecodeAccelerator::Client>(client));
    client_ = client_ptr_factory_->GetWeakPtr();
    // If we haven't been set up to decode on separate thread via
    // TryToSetupDecodeOnSeparateThread(), use the main thread/client for
    // decode tasks.
    if (!decode_task_runner_) {
      decode_task_runner_ = child_task_runner_;
      DCHECK(!decode_client_);
      decode_client_ = client_;
    }
  
    video_profile_ = config.profile;
  
    if (video_profile_ >= media::H264PROFILE_MIN &&
        video_profile_ <= media::H264PROFILE_MAX) {
      h264_accelerator_.reset(new V4L2H264Accelerator(this));
      decoder_.reset(new H264Decoder(h264_accelerator_.get()));
    } else if (video_profile_ >= media::VP8PROFILE_MIN &&
               video_profile_ <= media::VP8PROFILE_MAX) {
      vp8_accelerator_.reset(new V4L2VP8Accelerator(this));
      decoder_.reset(new VP8Decoder(vp8_accelerator_.get()));
    } else {
      NOTREACHED() << "Unsupported profile " << video_profile_;
      return false;
    }
  
    // TODO(posciak): This needs to be queried once supported.
    input_planes_count_ = 1;
    output_planes_count_ = 1;
  
    if (egl_display_ == EGL_NO_DISPLAY) {
      LOG(ERROR) << "Initialize(): could not get EGLDisplay";
      return false;
    }
  
    // We need the context to be initialized to query extensions.
    if (!make_context_current_cb_.is_null()) {
      if (!make_context_current_cb_.Run()) {
        LOG(ERROR) << "Initialize(): could not make context current";
        return false;
      }
  
      if (!gfx::g_driver_egl.ext.b_EGL_KHR_fence_sync) {
        LOG(ERROR) << "Initialize(): context does not have EGL_KHR_fence_sync";
        return false;
      }
    } else {
      DVLOG(1) << "No GL callbacks provided, initializing without GL support";
    }
  
    // Capabilities check.
    struct v4l2_capability caps;
    const __u32 kCapsRequired = V4L2_CAP_VIDEO_M2M_MPLANE | V4L2_CAP_STREAMING;
    IOCTL_OR_ERROR_RETURN_FALSE(VIDIOC_QUERYCAP, &caps);
    if ((caps.capabilities & kCapsRequired) != kCapsRequired) {
      LOG(ERROR) << "Initialize(): ioctl() failed: VIDIOC_QUERYCAP"
                 << ", caps check failed: 0x" << std::hex << caps.capabilities;
      return false;
    }
  
    if (!SetupFormats())
      return false;
  
    if (!decoder_thread_.Start()) {
      DLOG(ERROR) << "Initialize(): device thread failed to start";
      return false;
    }
    decoder_thread_task_runner_ = decoder_thread_.task_runner();
  
    state_ = kInitialized;
    output_mode_ = config.output_mode;
  
    // InitializeTask will NOTIFY_ERROR on failure.
    decoder_thread_task_runner_->PostTask(
        FROM_HERE, base::Bind(&V4L2SliceVideoDecodeAccelerator::InitializeTask,
                              base::Unretained(this)));
  
    DVLOGF(1) << "V4L2SliceVideoDecodeAccelerator initialized";
    return true;
  }
  
  void V4L2SliceVideoDecodeAccelerator::InitializeTask() {
    DVLOGF(3);
    DCHECK(decoder_thread_task_runner_->BelongsToCurrentThread());
    DCHECK_EQ(state_, kInitialized);
  
    if (!CreateInputBuffers())
      NOTIFY_ERROR(PLATFORM_FAILURE);
  
    // Output buffers will be created once decoder gives us information
    // about their size and required count.
    state_ = kDecoding;
  }
  
  void V4L2SliceVideoDecodeAccelerator::Destroy() {
    DVLOGF(3);
    DCHECK(child_task_runner_->BelongsToCurrentThread());
  
    if (decoder_thread_.IsRunning()) {
      decoder_thread_task_runner_->PostTask(
          FROM_HERE, base::Bind(&V4L2SliceVideoDecodeAccelerator::DestroyTask,
                                base::Unretained(this)));
  
      // Wait for tasks to finish/early-exit.
      decoder_thread_.Stop();
    }
  
    delete this;
    DVLOGF(3) << "Destroyed";
  }
  
  void V4L2SliceVideoDecodeAccelerator::DestroyTask() {
    DVLOGF(3);
    DCHECK(decoder_thread_task_runner_->BelongsToCurrentThread());
  
    state_ = kError;
  
    decoder_->Reset();
  
    decoder_current_bitstream_buffer_.reset();
    while (!decoder_input_queue_.empty())
      decoder_input_queue_.pop();
  
    // Stop streaming and the device_poll_thread_.
    StopDevicePoll(false);
  
    DestroyInputBuffers();
    DestroyOutputs(false);
  
    DCHECK(surfaces_at_device_.empty());
    DCHECK(surfaces_at_display_.empty());
    DCHECK(decoder_display_queue_.empty());
  }
  
  bool V4L2SliceVideoDecodeAccelerator::SetupFormats() {
    DCHECK_EQ(state_, kUninitialized);
  
    __u32 input_format_fourcc =
        V4L2Device::VideoCodecProfileToV4L2PixFmt(video_profile_, true);
    if (!input_format_fourcc) {
      NOTREACHED();
      return false;
    }
  
    size_t input_size;
    gfx::Size max_resolution, min_resolution;
    device_->GetSupportedResolution(input_format_fourcc, &min_resolution,
                                    &max_resolution);
    if (max_resolution.width() > 1920 && max_resolution.height() > 1088)
      input_size = kInputBufferMaxSizeFor4k;
    else
      input_size = kInputBufferMaxSizeFor1080p;
  
    struct v4l2_fmtdesc fmtdesc;
    memset(&fmtdesc, 0, sizeof(fmtdesc));
    fmtdesc.type = V4L2_BUF_TYPE_VIDEO_OUTPUT_MPLANE;
    bool is_format_supported = false;
    while (device_->Ioctl(VIDIOC_ENUM_FMT, &fmtdesc) == 0) {
      if (fmtdesc.pixelformat == input_format_fourcc) {
        is_format_supported = true;
        break;
      }
      ++fmtdesc.index;
    }
  
    if (!is_format_supported) {
      DVLOG(1) << "Input fourcc " << input_format_fourcc
               << " not supported by device.";
      return false;
    }
  
    struct v4l2_format format;
    memset(&format, 0, sizeof(format));
    format.type = V4L2_BUF_TYPE_VIDEO_OUTPUT_MPLANE;
    format.fmt.pix_mp.pixelformat = input_format_fourcc;
    format.fmt.pix_mp.plane_fmt[0].sizeimage = input_size;
    format.fmt.pix_mp.num_planes = input_planes_count_;
    IOCTL_OR_ERROR_RETURN_FALSE(VIDIOC_S_FMT, &format);
  
    // We have to set up the format for output, because the driver may not allow
    // changing it once we start streaming; whether it can support our chosen
    // output format or not may depend on the input format.
    memset(&fmtdesc, 0, sizeof(fmtdesc));
    fmtdesc.type = V4L2_BUF_TYPE_VIDEO_CAPTURE_MPLANE;
    output_format_fourcc_ = 0;
    while (device_->Ioctl(VIDIOC_ENUM_FMT, &fmtdesc) == 0) {
      if (device_->CanCreateEGLImageFrom(fmtdesc.pixelformat)) {
        output_format_fourcc_ = fmtdesc.pixelformat;
        break;
      }
      ++fmtdesc.index;
    }
  
    if (output_format_fourcc_ == 0) {
      LOG(ERROR) << "Could not find a usable output format";
      return false;
    }
  
    // Only set fourcc for output; resolution, etc., will come from the
    // driver once it extracts it from the stream.
    memset(&format, 0, sizeof(format));
    format.type = V4L2_BUF_TYPE_VIDEO_CAPTURE_MPLANE;
    format.fmt.pix_mp.pixelformat = output_format_fourcc_;
    format.fmt.pix_mp.num_planes = output_planes_count_;
    IOCTL_OR_ERROR_RETURN_FALSE(VIDIOC_S_FMT, &format);
  
    return true;
  }
  
  bool V4L2SliceVideoDecodeAccelerator::CreateInputBuffers() {
    DVLOGF(3);
    DCHECK(decoder_thread_task_runner_->BelongsToCurrentThread());
    DCHECK(!input_streamon_);
    DCHECK(input_buffer_map_.empty());
  
    struct v4l2_requestbuffers reqbufs;
    memset(&reqbufs, 0, sizeof(reqbufs));
    reqbufs.count = kNumInputBuffers;
    reqbufs.type = V4L2_BUF_TYPE_VIDEO_OUTPUT_MPLANE;
    reqbufs.memory = V4L2_MEMORY_MMAP;
    IOCTL_OR_ERROR_RETURN_FALSE(VIDIOC_REQBUFS, &reqbufs);
    if (reqbufs.count < kNumInputBuffers) {
      PLOG(ERROR) << "Could not allocate enough output buffers";
      return false;
    }
    input_buffer_map_.resize(reqbufs.count);
    for (size_t i = 0; i < input_buffer_map_.size(); ++i) {
      free_input_buffers_.push_back(i);
  
      // Query for the MEMORY_MMAP pointer.
      struct v4l2_plane planes[VIDEO_MAX_PLANES];
      struct v4l2_buffer buffer;
      memset(&buffer, 0, sizeof(buffer));
      memset(planes, 0, sizeof(planes));
      buffer.index = i;
      buffer.type = V4L2_BUF_TYPE_VIDEO_OUTPUT_MPLANE;
      buffer.memory = V4L2_MEMORY_MMAP;
      buffer.m.planes = planes;
      buffer.length = input_planes_count_;
      IOCTL_OR_ERROR_RETURN_FALSE(VIDIOC_QUERYBUF, &buffer);
      void* address = device_->Mmap(nullptr,
                                    buffer.m.planes[0].length,
                                    PROT_READ | PROT_WRITE,
                                    MAP_SHARED,
                                    buffer.m.planes[0].m.mem_offset);
      if (address == MAP_FAILED) {
        PLOG(ERROR) << "CreateInputBuffers(): mmap() failed";
        return false;
      }
      input_buffer_map_[i].address = address;
      input_buffer_map_[i].length = buffer.m.planes[0].length;
    }
  
    return true;
  }
  
  bool V4L2SliceVideoDecodeAccelerator::CreateOutputBuffers() {
    DVLOGF(3);
    DCHECK(decoder_thread_task_runner_->BelongsToCurrentThread());
    DCHECK(!output_streamon_);
    DCHECK(output_buffer_map_.empty());
    DCHECK(surfaces_at_display_.empty());
    DCHECK(surfaces_at_device_.empty());
  
    visible_size_ = decoder_->GetPicSize();
    size_t num_pictures = decoder_->GetRequiredNumOfPictures();
  
    DCHECK_GT(num_pictures, 0u);
    DCHECK(!visible_size_.IsEmpty());
  
    struct v4l2_format format;
    memset(&format, 0, sizeof(format));
    format.type = V4L2_BUF_TYPE_VIDEO_CAPTURE_MPLANE;
    format.fmt.pix_mp.pixelformat = output_format_fourcc_;
    format.fmt.pix_mp.width = visible_size_.width();
    format.fmt.pix_mp.height = visible_size_.height();
    format.fmt.pix_mp.num_planes = input_planes_count_;
  
    if (device_->Ioctl(VIDIOC_S_FMT, &format) != 0) {
      PLOG(ERROR) << "Failed setting format to: " << output_format_fourcc_;
      NOTIFY_ERROR(PLATFORM_FAILURE);
      return false;
    }
  
    coded_size_.SetSize(base::checked_cast<int>(format.fmt.pix_mp.width),
                        base::checked_cast<int>(format.fmt.pix_mp.height));
    DCHECK_EQ(coded_size_.width() % 16, 0);
    DCHECK_EQ(coded_size_.height() % 16, 0);
  
    if (!gfx::Rect(coded_size_).Contains(gfx::Rect(visible_size_))) {
      LOG(ERROR) << "Got invalid adjusted coded size: " << coded_size_.ToString();
      return false;
    }
  
    DVLOGF(3) << "buffer_count=" << num_pictures
              << ", visible size=" << visible_size_.ToString()
              << ", coded size=" << coded_size_.ToString();
  
    child_task_runner_->PostTask(
        FROM_HERE,
        base::Bind(&VideoDecodeAccelerator::Client::ProvidePictureBuffers,
                   client_, num_pictures, 1, coded_size_,
                   device_->GetTextureTarget()));
  
    // Go into kAwaitingPictureBuffers to prevent us from doing any more decoding
    // or event handling while we are waiting for AssignPictureBuffers(). Not
    // having Pictures available would not have prevented us from making decoding
    // progress entirely e.g. in the case of H.264 where we could further decode
    // non-slice NALUs and could even get another resolution change before we were
    // done with this one. After we get the buffers, we'll go back into kIdle and
    // kick off further event processing, and eventually go back into kDecoding
    // once no more events are pending (if any).
    state_ = kAwaitingPictureBuffers;
    return true;
  }
  
  void V4L2SliceVideoDecodeAccelerator::DestroyInputBuffers() {
    DVLOGF(3);
    DCHECK(decoder_thread_task_runner_->BelongsToCurrentThread() ||
           !decoder_thread_.IsRunning());
    DCHECK(!input_streamon_);
  
    for (auto& input_record : input_buffer_map_) {
      if (input_record.address != nullptr)
        device_->Munmap(input_record.address, input_record.length);
    }
  
    struct v4l2_requestbuffers reqbufs;
    memset(&reqbufs, 0, sizeof(reqbufs));
    reqbufs.count = 0;
    reqbufs.type = V4L2_BUF_TYPE_VIDEO_OUTPUT_MPLANE;
    reqbufs.memory = V4L2_MEMORY_MMAP;
    IOCTL_OR_LOG_ERROR(VIDIOC_REQBUFS, &reqbufs);
  
    input_buffer_map_.clear();
    free_input_buffers_.clear();
  }
  
  void V4L2SliceVideoDecodeAccelerator::DismissPictures(
      const std::vector<int32_t>& picture_buffer_ids,
      base::WaitableEvent* done) {
    DVLOGF(3);
    DCHECK(child_task_runner_->BelongsToCurrentThread());
  
    for (auto picture_buffer_id : picture_buffer_ids) {
      DVLOGF(1) << "dismissing PictureBuffer id=" << picture_buffer_id;
      client_->DismissPictureBuffer(picture_buffer_id);
    }
  
    done->Signal();
  }
  
  void V4L2SliceVideoDecodeAccelerator::DevicePollTask(bool poll_device) {
    DVLOGF(4);
    DCHECK_EQ(device_poll_thread_.message_loop(), base::MessageLoop::current());
  
    bool event_pending;
    if (!device_->Poll(poll_device, &event_pending)) {
      NOTIFY_ERROR(PLATFORM_FAILURE);
      return;
    }
  
    // All processing should happen on ServiceDeviceTask(), since we shouldn't
    // touch encoder state from this thread.
    decoder_thread_task_runner_->PostTask(
        FROM_HERE, base::Bind(&V4L2SliceVideoDecodeAccelerator::ServiceDeviceTask,
                              base::Unretained(this)));
  }
  
  void V4L2SliceVideoDecodeAccelerator::ServiceDeviceTask() {
    DVLOGF(4);
    DCHECK(decoder_thread_task_runner_->BelongsToCurrentThread());
  
    // ServiceDeviceTask() should only ever be scheduled from DevicePollTask().
  
    Dequeue();
    SchedulePollIfNeeded();
  }
  
  void V4L2SliceVideoDecodeAccelerator::SchedulePollIfNeeded() {
    DCHECK(decoder_thread_task_runner_->BelongsToCurrentThread());
  
    if (!device_poll_thread_.IsRunning()) {
      DVLOGF(2) << "Device poll thread stopped, will not schedule poll";
      return;
    }
  
    DCHECK(input_streamon_ || output_streamon_);
  
    if (input_buffer_queued_count_ + output_buffer_queued_count_ == 0) {
      DVLOGF(4) << "No buffers queued, will not schedule poll";
      return;
    }
  
    DVLOGF(4) << "Scheduling device poll task";
  
    device_poll_thread_.message_loop()->PostTask(
        FROM_HERE, base::Bind(&V4L2SliceVideoDecodeAccelerator::DevicePollTask,
                              base::Unretained(this), true));
  
    DVLOGF(2) << "buffer counts: "
              << "INPUT[" << decoder_input_queue_.size() << "]"
              << " => DEVICE["
              << free_input_buffers_.size() << "+"
              << input_buffer_queued_count_ << "/"
              << input_buffer_map_.size() << "]->["
              << free_output_buffers_.size() << "+"
              << output_buffer_queued_count_ << "/"
              << output_buffer_map_.size() << "]"
              << " => DISPLAYQ[" << decoder_display_queue_.size() << "]"
              << " => CLIENT[" << surfaces_at_display_.size() << "]";
  }
  
  void V4L2SliceVideoDecodeAccelerator::Enqueue(
      const scoped_refptr<V4L2DecodeSurface>& dec_surface) {
    DCHECK(decoder_thread_task_runner_->BelongsToCurrentThread());
  
    const int old_inputs_queued = input_buffer_queued_count_;
    const int old_outputs_queued = output_buffer_queued_count_;
  
    if (!EnqueueInputRecord(dec_surface->input_record(),
                            dec_surface->config_store())) {
      DVLOGF(1) << "Failed queueing an input buffer";
      NOTIFY_ERROR(PLATFORM_FAILURE);
      return;
    }
  
    if (!EnqueueOutputRecord(dec_surface->output_record())) {
      DVLOGF(1) << "Failed queueing an output buffer";
      NOTIFY_ERROR(PLATFORM_FAILURE);
      return;
    }
  
    bool inserted =
        surfaces_at_device_
            .insert(std::make_pair(dec_surface->output_record(), dec_surface))
            .second;
    DCHECK(inserted);
  
    if (old_inputs_queued == 0 && old_outputs_queued == 0)
      SchedulePollIfNeeded();
  }
  
  void V4L2SliceVideoDecodeAccelerator::Dequeue() {
    DVLOGF(3);
    DCHECK(decoder_thread_task_runner_->BelongsToCurrentThread());
  
    struct v4l2_buffer dqbuf;
    struct v4l2_plane planes[VIDEO_MAX_PLANES];
    while (input_buffer_queued_count_ > 0) {
      DCHECK(input_streamon_);
      memset(&dqbuf, 0, sizeof(dqbuf));
      memset(&planes, 0, sizeof(planes));
      dqbuf.type = V4L2_BUF_TYPE_VIDEO_OUTPUT_MPLANE;
      dqbuf.memory = V4L2_MEMORY_MMAP;
      dqbuf.m.planes = planes;
      dqbuf.length = input_planes_count_;
      if (device_->Ioctl(VIDIOC_DQBUF, &dqbuf) != 0) {
        if (errno == EAGAIN) {
          // EAGAIN if we're just out of buffers to dequeue.
          break;
        }
        PLOG(ERROR) << "ioctl() failed: VIDIOC_DQBUF";
        NOTIFY_ERROR(PLATFORM_FAILURE);
        return;
      }
      InputRecord& input_record = input_buffer_map_[dqbuf.index];
      DCHECK(input_record.at_device);
      input_record.at_device = false;
      ReuseInputBuffer(dqbuf.index);
      input_buffer_queued_count_--;
      DVLOGF(4) << "Dequeued input=" << dqbuf.index
                << " count: " << input_buffer_queued_count_;
    }
  
    while (output_buffer_queued_count_ > 0) {
      DCHECK(output_streamon_);
      memset(&dqbuf, 0, sizeof(dqbuf));
      memset(&planes, 0, sizeof(planes));
      dqbuf.type = V4L2_BUF_TYPE_VIDEO_CAPTURE_MPLANE;
      dqbuf.memory =
          (output_mode_ == Config::OutputMode::ALLOCATE ? V4L2_MEMORY_MMAP
                                                        : V4L2_MEMORY_DMABUF);
      dqbuf.m.planes = planes;
      dqbuf.length = output_planes_count_;
      if (device_->Ioctl(VIDIOC_DQBUF, &dqbuf) != 0) {
        if (errno == EAGAIN) {
          // EAGAIN if we're just out of buffers to dequeue.
          break;
        }
        PLOG(ERROR) << "ioctl() failed: VIDIOC_DQBUF";
        NOTIFY_ERROR(PLATFORM_FAILURE);
        return;
      }
      OutputRecord& output_record = output_buffer_map_[dqbuf.index];
      DCHECK(output_record.at_device);
      output_record.at_device = false;
      output_buffer_queued_count_--;
      DVLOGF(3) << "Dequeued output=" << dqbuf.index
                << " count " << output_buffer_queued_count_;
  
      V4L2DecodeSurfaceByOutputId::iterator it =
          surfaces_at_device_.find(dqbuf.index);
      if (it == surfaces_at_device_.end()) {
        DLOG(ERROR) << "Got invalid surface from device.";
        NOTIFY_ERROR(PLATFORM_FAILURE);
      }
  
      it->second->SetDecoded();
      surfaces_at_device_.erase(it);
    }
  
    // A frame was decoded, see if we can output it.
    TryOutputSurfaces();
  
    ProcessPendingEventsIfNeeded();
  }
  
  void V4L2SliceVideoDecodeAccelerator::NewEventPending() {
    // Switch to event processing mode if we are decoding. Otherwise we are either
    // already in it, or we will potentially switch to it later, after finishing
    // other tasks.
    if (state_ == kDecoding)
      state_ = kIdle;
  
    ProcessPendingEventsIfNeeded();
  }
  
  bool V4L2SliceVideoDecodeAccelerator::FinishEventProcessing() {
    DCHECK_EQ(state_, kIdle);
  
    state_ = kDecoding;
    ScheduleDecodeBufferTaskIfNeeded();
  
    return true;
  }
  
  void V4L2SliceVideoDecodeAccelerator::ProcessPendingEventsIfNeeded() {
    DCHECK(decoder_thread_task_runner_->BelongsToCurrentThread());
  
    // Process pending events, if any, in the correct order.
    // We always first process the surface set change, as it is an internal
    // event from the decoder and interleaving it with external requests would
    // put the decoder in an undefined state.
    using ProcessFunc = bool (V4L2SliceVideoDecodeAccelerator::*)();
    const ProcessFunc process_functions[] = {
        &V4L2SliceVideoDecodeAccelerator::FinishSurfaceSetChange,
        &V4L2SliceVideoDecodeAccelerator::FinishFlush,
        &V4L2SliceVideoDecodeAccelerator::FinishReset,
        &V4L2SliceVideoDecodeAccelerator::FinishEventProcessing,
    };
  
    for (const auto& fn : process_functions) {
      if (state_ != kIdle)
        return;
  
      if (!(this->*fn)())
        return;
    }
  }
  
  void V4L2SliceVideoDecodeAccelerator::ReuseInputBuffer(int index) {
    DVLOGF(4) << "Reusing input buffer, index=" << index;
    DCHECK(decoder_thread_task_runner_->BelongsToCurrentThread());
  
    DCHECK_LT(index, static_cast<int>(input_buffer_map_.size()));
    InputRecord& input_record = input_buffer_map_[index];
  
    DCHECK(!input_record.at_device);
    input_record.input_id = -1;
    input_record.bytes_used = 0;
  
    DCHECK_EQ(
        std::count(free_input_buffers_.begin(), free_input_buffers_.end(), index),
        0);
    free_input_buffers_.push_back(index);
  }
  
  void V4L2SliceVideoDecodeAccelerator::ReuseOutputBuffer(int index) {
    DVLOGF(4) << "Reusing output buffer, index=" << index;
    DCHECK(decoder_thread_task_runner_->BelongsToCurrentThread());
  
    DCHECK_LT(index, static_cast<int>(output_buffer_map_.size()));
    OutputRecord& output_record = output_buffer_map_[index];
    DCHECK(!output_record.at_device);
    DCHECK(!output_record.at_client);
  
    DCHECK_EQ(std::count(free_output_buffers_.begin(), free_output_buffers_.end(),
                         index),
              0);
    free_output_buffers_.push_back(index);
  
    ScheduleDecodeBufferTaskIfNeeded();
  }
  
  bool V4L2SliceVideoDecodeAccelerator::EnqueueInputRecord(
      int index,
      uint32_t config_store) {
    DVLOGF(3);
    DCHECK_LT(index, static_cast<int>(input_buffer_map_.size()));
    DCHECK_GT(config_store, 0u);
  
    // Enqueue an input (VIDEO_OUTPUT) buffer for an input video frame.
    InputRecord& input_record = input_buffer_map_[index];
    DCHECK(!input_record.at_device);
    struct v4l2_buffer qbuf;
    struct v4l2_plane qbuf_planes[VIDEO_MAX_PLANES];
    memset(&qbuf, 0, sizeof(qbuf));
    memset(qbuf_planes, 0, sizeof(qbuf_planes));
    qbuf.index = index;
    qbuf.type = V4L2_BUF_TYPE_VIDEO_OUTPUT_MPLANE;
    qbuf.memory = V4L2_MEMORY_MMAP;
    qbuf.m.planes = qbuf_planes;
    qbuf.m.planes[0].bytesused = input_record.bytes_used;
    qbuf.length = input_planes_count_;
    qbuf.config_store = config_store;
    IOCTL_OR_ERROR_RETURN_FALSE(VIDIOC_QBUF, &qbuf);
    input_record.at_device = true;
    input_buffer_queued_count_++;
    DVLOGF(4) << "Enqueued input=" << qbuf.index
              << " count: " << input_buffer_queued_count_;
  
    return true;
  }
  
  bool V4L2SliceVideoDecodeAccelerator::EnqueueOutputRecord(int index) {
    DVLOGF(3);
    DCHECK_LT(index, static_cast<int>(output_buffer_map_.size()));
  
    // Enqueue an output (VIDEO_CAPTURE) buffer.
    OutputRecord& output_record = output_buffer_map_[index];
    DCHECK(!output_record.at_device);
    DCHECK(!output_record.at_client);
    DCHECK_NE(output_record.picture_id, -1);
  
    if (output_record.egl_sync != EGL_NO_SYNC_KHR) {
      // If we have to wait for completion, wait.  Note that
      // free_output_buffers_ is a FIFO queue, so we always wait on the
      // buffer that has been in the queue the longest.
      if (eglClientWaitSyncKHR(egl_display_, output_record.egl_sync, 0,
                               EGL_FOREVER_KHR) == EGL_FALSE) {
        // This will cause tearing, but is safe otherwise.
        DVLOGF(1) << "eglClientWaitSyncKHR failed!";
      }
      if (eglDestroySyncKHR(egl_display_, output_record.egl_sync) != EGL_TRUE) {
        LOGF(ERROR) << "eglDestroySyncKHR failed!";
        NOTIFY_ERROR(PLATFORM_FAILURE);
        return false;
      }
      output_record.egl_sync = EGL_NO_SYNC_KHR;
    }
  
    struct v4l2_buffer qbuf;
    struct v4l2_plane qbuf_planes[VIDEO_MAX_PLANES];
    memset(&qbuf, 0, sizeof(qbuf));
    memset(qbuf_planes, 0, sizeof(qbuf_planes));
    qbuf.index = index;
    qbuf.type = V4L2_BUF_TYPE_VIDEO_CAPTURE_MPLANE;
    if (output_mode_ == Config::OutputMode::ALLOCATE) {
      qbuf.memory = V4L2_MEMORY_MMAP;
    } else {
      qbuf.memory = V4L2_MEMORY_DMABUF;
      DCHECK_EQ(output_planes_count_, output_record.dmabuf_fds.size());
      for (size_t i = 0; i < output_record.dmabuf_fds.size(); ++i) {
        DCHECK(output_record.dmabuf_fds[i].is_valid());
        qbuf_planes[i].m.fd = output_record.dmabuf_fds[i].get();
      }
    }
    qbuf.m.planes = qbuf_planes;
    qbuf.length = output_planes_count_;
    IOCTL_OR_ERROR_RETURN_FALSE(VIDIOC_QBUF, &qbuf);
    output_record.at_device = true;
    output_buffer_queued_count_++;
    DVLOGF(4) << "Enqueued output=" << qbuf.index
              << " count: " << output_buffer_queued_count_;
  
    return true;
  }
  
  bool V4L2SliceVideoDecodeAccelerator::StartDevicePoll() {
    DVLOGF(3) << "Starting device poll";
    DCHECK(decoder_thread_task_runner_->BelongsToCurrentThread());
    DCHECK(!device_poll_thread_.IsRunning());
  
    // Start up the device poll thread and schedule its first DevicePollTask().
    if (!device_poll_thread_.Start()) {
      DLOG(ERROR) << "StartDevicePoll(): Device thread failed to start";
      NOTIFY_ERROR(PLATFORM_FAILURE);
      return false;
    }
    if (!input_streamon_) {
      __u32 type = V4L2_BUF_TYPE_VIDEO_OUTPUT_MPLANE;
      IOCTL_OR_ERROR_RETURN_FALSE(VIDIOC_STREAMON, &type);
      input_streamon_ = true;
    }
  
    if (!output_streamon_) {
      __u32 type = V4L2_BUF_TYPE_VIDEO_CAPTURE_MPLANE;
      IOCTL_OR_ERROR_RETURN_FALSE(VIDIOC_STREAMON, &type);
      output_streamon_ = true;
    }
  
    device_poll_thread_.message_loop()->PostTask(
        FROM_HERE, base::Bind(&V4L2SliceVideoDecodeAccelerator::DevicePollTask,
                              base::Unretained(this), true));
  
    return true;
  }
  
  bool V4L2SliceVideoDecodeAccelerator::StopDevicePoll(bool keep_input_state) {
    DVLOGF(3) << "Stopping device poll";
    if (decoder_thread_.IsRunning())
      DCHECK(decoder_thread_task_runner_->BelongsToCurrentThread());
  
    // Signal the DevicePollTask() to stop, and stop the device poll thread.
    if (!device_->SetDevicePollInterrupt()) {
      PLOG(ERROR) << "SetDevicePollInterrupt(): failed";
      NOTIFY_ERROR(PLATFORM_FAILURE);
      return false;
    }
    device_poll_thread_.Stop();
    DVLOGF(3) << "Device poll thread stopped";
  
    // Clear the interrupt now, to be sure.
    if (!device_->ClearDevicePollInterrupt()) {
      NOTIFY_ERROR(PLATFORM_FAILURE);
      return false;
    }
  
    if (!keep_input_state) {
      if (input_streamon_) {
        __u32 type = V4L2_BUF_TYPE_VIDEO_OUTPUT_MPLANE;
        IOCTL_OR_ERROR_RETURN_FALSE(VIDIOC_STREAMOFF, &type);
      }
      input_streamon_ = false;
    }
  
    if (output_streamon_) {
      __u32 type = V4L2_BUF_TYPE_VIDEO_CAPTURE_MPLANE;
      IOCTL_OR_ERROR_RETURN_FALSE(VIDIOC_STREAMOFF, &type);
    }
    output_streamon_ = false;
  
    if (!keep_input_state) {
      for (size_t i = 0; i < input_buffer_map_.size(); ++i) {
        InputRecord& input_record = input_buffer_map_[i];
        if (input_record.at_device) {
          input_record.at_device = false;
          ReuseInputBuffer(i);
          input_buffer_queued_count_--;
        }
      }
      DCHECK_EQ(input_buffer_queued_count_, 0);
    }
  
    // STREAMOFF makes the driver drop all buffers without decoding and DQBUFing,
    // so we mark them all as at_device = false and clear surfaces_at_device_.
    for (size_t i = 0; i < output_buffer_map_.size(); ++i) {
      OutputRecord& output_record = output_buffer_map_[i];
      if (output_record.at_device) {
        output_record.at_device = false;
        output_buffer_queued_count_--;
      }
    }
    surfaces_at_device_.clear();
    DCHECK_EQ(output_buffer_queued_count_, 0);
  
    // Drop all surfaces that were awaiting decode before being displayed,
    // since we've just cancelled all outstanding decodes.
    while (!decoder_display_queue_.empty())
      decoder_display_queue_.pop();
  
    DVLOGF(3) << "Device poll stopped";
    return true;
  }
  
  void V4L2SliceVideoDecodeAccelerator::Decode(
      const media::BitstreamBuffer& bitstream_buffer) {
    DVLOGF(3) << "input_id=" << bitstream_buffer.id()
              << ", size=" << bitstream_buffer.size();
    DCHECK(decode_task_runner_->BelongsToCurrentThread());
  
    if (bitstream_buffer.id() < 0) {
      LOG(ERROR) << "Invalid bitstream_buffer, id: " << bitstream_buffer.id();
      if (base::SharedMemory::IsHandleValid(bitstream_buffer.handle()))
        base::SharedMemory::CloseHandle(bitstream_buffer.handle());
      NOTIFY_ERROR(INVALID_ARGUMENT);
      return;
    }
  
    decoder_thread_task_runner_->PostTask(
        FROM_HERE, base::Bind(&V4L2SliceVideoDecodeAccelerator::DecodeTask,
                              base::Unretained(this), bitstream_buffer));
  }
  
  void V4L2SliceVideoDecodeAccelerator::DecodeTask(
      const media::BitstreamBuffer& bitstream_buffer) {
    DVLOGF(3) << "input_id=" << bitstream_buffer.id()
              << " size=" << bitstream_buffer.size();
    DCHECK(decoder_thread_task_runner_->BelongsToCurrentThread());
  
    std::unique_ptr<BitstreamBufferRef> bitstream_record(new BitstreamBufferRef(
        decode_client_, decode_task_runner_,
        new SharedMemoryRegion(bitstream_buffer, true), bitstream_buffer.id()));
  
    // Skip empty buffer.
    if (bitstream_buffer.size() == 0)
      return;
  
    if (!bitstream_record->shm->Map()) {
      LOGF(ERROR) << "Could not map bitstream_buffer";
      NOTIFY_ERROR(UNREADABLE_INPUT);
      return;
    }
    DVLOGF(3) << "mapped at=" << bitstream_record->shm->memory();
  
    decoder_input_queue_.push(
        linked_ptr<BitstreamBufferRef>(bitstream_record.release()));
  
    ScheduleDecodeBufferTaskIfNeeded();
  }
  
  bool V4L2SliceVideoDecodeAccelerator::TrySetNewBistreamBuffer() {
    DCHECK(decoder_thread_task_runner_->BelongsToCurrentThread());
    DCHECK(!decoder_current_bitstream_buffer_);
  
    if (decoder_input_queue_.empty())
      return false;
  
    decoder_current_bitstream_buffer_.reset(
        decoder_input_queue_.front().release());
    decoder_input_queue_.pop();
  
    if (decoder_current_bitstream_buffer_->input_id == kFlushBufferId) {
      // This is a buffer we queued for ourselves to trigger flush at this time.
      InitiateFlush();
      return false;
    }
  
    const uint8_t* const data = reinterpret_cast<const uint8_t*>(
        decoder_current_bitstream_buffer_->shm->memory());
    const size_t data_size = decoder_current_bitstream_buffer_->shm->size();
    decoder_->SetStream(data, data_size);
  
    return true;
  }
  
  void V4L2SliceVideoDecodeAccelerator::ScheduleDecodeBufferTaskIfNeeded() {
    DCHECK(decoder_thread_task_runner_->BelongsToCurrentThread());
    if (state_ == kDecoding) {
      decoder_thread_task_runner_->PostTask(
          FROM_HERE,
          base::Bind(&V4L2SliceVideoDecodeAccelerator::DecodeBufferTask,
                     base::Unretained(this)));
    }
  }
  
  void V4L2SliceVideoDecodeAccelerator::DecodeBufferTask() {
    DVLOGF(3);
    DCHECK(decoder_thread_task_runner_->BelongsToCurrentThread());
  
    if (state_ != kDecoding) {
      DVLOGF(3) << "Early exit, not in kDecoding";
      return;
    }
  
    while (true) {
      AcceleratedVideoDecoder::DecodeResult res;
      res = decoder_->Decode();
      switch (res) {
        case AcceleratedVideoDecoder::kAllocateNewSurfaces:
          DVLOGF(2) << "Decoder requesting a new set of surfaces";
          InitiateSurfaceSetChange();
          return;
  
        case AcceleratedVideoDecoder::kRanOutOfStreamData:
          decoder_current_bitstream_buffer_.reset();
          if (!TrySetNewBistreamBuffer())
            return;
  
          break;
  
        case AcceleratedVideoDecoder::kRanOutOfSurfaces:
          // No more surfaces for the decoder, we'll come back once we have more.
          DVLOGF(4) << "Ran out of surfaces";
          return;
  
        case AcceleratedVideoDecoder::kDecodeError:
          DVLOGF(1) << "Error decoding stream";
          NOTIFY_ERROR(PLATFORM_FAILURE);
          return;
      }
    }
  }
  
  void V4L2SliceVideoDecodeAccelerator::InitiateSurfaceSetChange() {
    DVLOGF(2);
    DCHECK(decoder_thread_task_runner_->BelongsToCurrentThread());
    DCHECK_EQ(state_, kDecoding);
  
    DCHECK(!surface_set_change_pending_);
    surface_set_change_pending_ = true;
    NewEventPending();
  }
  
  bool V4L2SliceVideoDecodeAccelerator::FinishSurfaceSetChange() {
    DVLOGF(2);
    DCHECK(decoder_thread_task_runner_->BelongsToCurrentThread());
  
    if (!surface_set_change_pending_)
      return true;
  
    if (!surfaces_at_device_.empty())
      return false;
  
    DCHECK_EQ(state_, kIdle);
    DCHECK(decoder_display_queue_.empty());
    // All output buffers should've been returned from decoder and device by now.
    // The only remaining owner of surfaces may be display (client), and we will
    // dismiss them when destroying output buffers below.
    DCHECK_EQ(free_output_buffers_.size() + surfaces_at_display_.size(),
              output_buffer_map_.size());
  
    // Keep input queue running while we switch outputs.
    if (!StopDevicePoll(true)) {
      NOTIFY_ERROR(PLATFORM_FAILURE);
      return false;
    }
  
    // This will return only once all buffers are dismissed and destroyed.
    // This does not wait until they are displayed however, as display retains
    // references to the buffers bound to textures and will release them
    // after displaying.
    if (!DestroyOutputs(true)) {
      NOTIFY_ERROR(PLATFORM_FAILURE);
      return false;
    }
  
    if (!CreateOutputBuffers()) {
      NOTIFY_ERROR(PLATFORM_FAILURE);
      return false;
    }
  
    surface_set_change_pending_ = false;
    DVLOG(3) << "Surface set change finished";
    return true;
  }
  
  bool V4L2SliceVideoDecodeAccelerator::DestroyOutputs(bool dismiss) {
    DVLOGF(3);
    DCHECK(decoder_thread_task_runner_->BelongsToCurrentThread());
    std::vector<int32_t> picture_buffers_to_dismiss;
  
    if (output_buffer_map_.empty())
      return true;
  
    for (const auto& output_record : output_buffer_map_) {
      DCHECK(!output_record.at_device);
  
      if (output_record.egl_sync != EGL_NO_SYNC_KHR) {
        if (eglDestroySyncKHR(egl_display_, output_record.egl_sync) != EGL_TRUE)
          DVLOGF(1) << "eglDestroySyncKHR failed.";
      }
  
      if (output_record.egl_image != EGL_NO_IMAGE_KHR) {
        child_task_runner_->PostTask(
            FROM_HERE,
            base::Bind(base::IgnoreResult(&V4L2Device::DestroyEGLImage), device_,
                       egl_display_, output_record.egl_image));
      }
  
      picture_buffers_to_dismiss.push_back(output_record.picture_id);
    }
  
    if (dismiss) {
      DVLOGF(2) << "Scheduling picture dismissal";
      base::WaitableEvent done(false, false);
      child_task_runner_->PostTask(
          FROM_HERE, base::Bind(&V4L2SliceVideoDecodeAccelerator::DismissPictures,
                                weak_this_, picture_buffers_to_dismiss, &done));
      done.Wait();
    }
  
    // At this point client can't call ReusePictureBuffer on any of the pictures
    // anymore, so it's safe to destroy.
    return DestroyOutputBuffers();
  }
  
  bool V4L2SliceVideoDecodeAccelerator::DestroyOutputBuffers() {
    DVLOGF(3);
    DCHECK(decoder_thread_task_runner_->BelongsToCurrentThread() ||
           !decoder_thread_.IsRunning());
    DCHECK(!output_streamon_);
    DCHECK(surfaces_at_device_.empty());
    DCHECK(decoder_display_queue_.empty());
    DCHECK_EQ(surfaces_at_display_.size() + free_output_buffers_.size(),
              output_buffer_map_.size());
  
    if (output_buffer_map_.empty())
      return true;
  
    // It's ok to do this, client will retain references to textures, but we are
    // not interested in reusing the surfaces anymore.
    // This will prevent us from reusing old surfaces in case we have some
    // ReusePictureBuffer() pending on ChildThread already. It's ok to ignore
    // them, because we have already dismissed them (in DestroyOutputs()).
    for (const auto& surface_at_display : surfaces_at_display_) {
      size_t index = surface_at_display.second->output_record();
      DCHECK_LT(index, output_buffer_map_.size());
      OutputRecord& output_record = output_buffer_map_[index];
      DCHECK(output_record.at_client);
      output_record.at_client = false;
    }
    surfaces_at_display_.clear();
    DCHECK_EQ(free_output_buffers_.size(), output_buffer_map_.size());
  
    free_output_buffers_.clear();
    output_buffer_map_.clear();
  
    struct v4l2_requestbuffers reqbufs;
    memset(&reqbufs, 0, sizeof(reqbufs));
    reqbufs.count = 0;
    reqbufs.type = V4L2_BUF_TYPE_VIDEO_CAPTURE_MPLANE;
    reqbufs.memory = V4L2_MEMORY_MMAP;
    IOCTL_OR_ERROR_RETURN_FALSE(VIDIOC_REQBUFS, &reqbufs);
  
    return true;
  }
  
  void V4L2SliceVideoDecodeAccelerator::AssignPictureBuffers(
      const std::vector<media::PictureBuffer>& buffers) {
    DVLOGF(3);
    DCHECK(child_task_runner_->BelongsToCurrentThread());
  
    decoder_thread_task_runner_->PostTask(
        FROM_HERE,
        base::Bind(&V4L2SliceVideoDecodeAccelerator::AssignPictureBuffersTask,
                   base::Unretained(this), buffers));
  }
  
  void V4L2SliceVideoDecodeAccelerator::AssignPictureBuffersTask(
      const std::vector<media::PictureBuffer>& buffers) {
    DVLOGF(3);
    DCHECK(decoder_thread_task_runner_->BelongsToCurrentThread());
    DCHECK_EQ(state_, kAwaitingPictureBuffers);
  
    const uint32_t req_buffer_count = decoder_->GetRequiredNumOfPictures();
  
    if (buffers.size() < req_buffer_count) {
      DLOG(ERROR) << "Failed to provide requested picture buffers. "
                  << "(Got " << buffers.size()
                  << ", requested " << req_buffer_count << ")";
      NOTIFY_ERROR(INVALID_ARGUMENT);
      return;
    }
  
    // Allocate the output buffers.
    struct v4l2_requestbuffers reqbufs;
    memset(&reqbufs, 0, sizeof(reqbufs));
    reqbufs.count = buffers.size();
    reqbufs.type = V4L2_BUF_TYPE_VIDEO_CAPTURE_MPLANE;
    reqbufs.memory =
        (output_mode_ == Config::OutputMode::ALLOCATE ? V4L2_MEMORY_MMAP
                                                      : V4L2_MEMORY_DMABUF);
    IOCTL_OR_ERROR_RETURN(VIDIOC_REQBUFS, &reqbufs);
  
    if (reqbufs.count != buffers.size()) {
      DLOG(ERROR) << "Could not allocate enough output buffers";
      NOTIFY_ERROR(PLATFORM_FAILURE);
      return;
    }
  
    DCHECK(free_output_buffers_.empty());
    DCHECK(output_buffer_map_.empty());
    output_buffer_map_.resize(buffers.size());
    for (size_t i = 0; i < output_buffer_map_.size(); ++i) {
      DCHECK(buffers[i].size() == coded_size_);
      DCHECK_EQ(1u, buffers[i].texture_ids().size());
  
      OutputRecord& output_record = output_buffer_map_[i];
      DCHECK(!output_record.at_device);
      DCHECK(!output_record.at_client);
      DCHECK_EQ(output_record.egl_image, EGL_NO_IMAGE_KHR);
      DCHECK_EQ(output_record.egl_sync, EGL_NO_SYNC_KHR);
      DCHECK_EQ(output_record.picture_id, -1);
      DCHECK(output_record.dmabuf_fds.empty());
      DCHECK_EQ(output_record.cleared, false);
  
      output_record.picture_id = buffers[i].id();
      output_record.texture_id = buffers[i].texture_ids()[0];
      // This will remain true until ImportBufferForPicture is called, either by
      // the client, or by ourselves, if we are allocating.
      output_record.at_client = true;
      if (output_mode_ == Config::OutputMode::ALLOCATE) {
        std::vector<base::ScopedFD> dmabuf_fds =
            std::move(device_->GetDmabufsForV4L2Buffer(
                i, output_planes_count_, V4L2_BUF_TYPE_VIDEO_CAPTURE_MPLANE));
        if (dmabuf_fds.empty()) {
          NOTIFY_ERROR(PLATFORM_FAILURE);
          return;
        }
  
        auto passed_dmabuf_fds(base::WrapUnique(
            new std::vector<base::ScopedFD>(std::move(dmabuf_fds))));
        ImportBufferForPictureTask(output_record.picture_id,
                                   std::move(passed_dmabuf_fds));
      }  // else we'll get triggered via ImportBufferForPicture() from client.
      DVLOGF(3) << "buffer[" << i << "]: picture_id=" << output_record.picture_id;
    }
  
    if (!StartDevicePoll()) {
      NOTIFY_ERROR(PLATFORM_FAILURE);
      return;
    }
  
    // Put us in kIdle to allow further event processing.
    // ProcessPendingEventsIfNeeded() will put us back into kDecoding after all
    // other pending events are processed successfully.
    state_ = kIdle;
    ProcessPendingEventsIfNeeded();
  }
  
  void V4L2SliceVideoDecodeAccelerator::CreateEGLImageFor(
      size_t buffer_index,
      int32_t picture_buffer_id,
      std::unique_ptr<std::vector<base::ScopedFD>> passed_dmabuf_fds,
      GLuint texture_id,
      const gfx::Size& size,
      uint32_t fourcc) {
    DVLOGF(3) << "index=" << buffer_index;
    DCHECK(child_task_runner_->BelongsToCurrentThread());
  
    if (get_gl_context_cb_.is_null() || make_context_current_cb_.is_null()) {
      DLOG(ERROR) << "GL callbacks required for binding to EGLImages";
      NOTIFY_ERROR(INVALID_ARGUMENT);
      return;
    }
  
    gfx::GLContext* gl_context = get_gl_context_cb_.Run();
    if (!gl_context || !make_context_current_cb_.Run()) {
      DLOG(ERROR) << "No GL context";
      NOTIFY_ERROR(PLATFORM_FAILURE);
      return;
    }
  
    gfx::ScopedTextureBinder bind_restore(GL_TEXTURE_EXTERNAL_OES, 0);
  
    EGLImageKHR egl_image =
        device_->CreateEGLImage(egl_display_, gl_context->GetHandle(), texture_id,
                                size, buffer_index, fourcc, *passed_dmabuf_fds);
    if (egl_image == EGL_NO_IMAGE_KHR) {
      LOGF(ERROR) << "Could not create EGLImageKHR,"
                  << " index=" << buffer_index << " texture_id=" << texture_id;
      NOTIFY_ERROR(PLATFORM_FAILURE);
      return;
    }
  
    decoder_thread_task_runner_->PostTask(
        FROM_HERE,
        base::Bind(&V4L2SliceVideoDecodeAccelerator::AssignEGLImage,
                   base::Unretained(this), buffer_index, picture_buffer_id,
                   egl_image, base::Passed(&passed_dmabuf_fds)));
  }
  
  void V4L2SliceVideoDecodeAccelerator::AssignEGLImage(
      size_t buffer_index,
      int32_t picture_buffer_id,
      EGLImageKHR egl_image,
      std::unique_ptr<std::vector<base::ScopedFD>> passed_dmabuf_fds) {
    DVLOGF(3) << "index=" << buffer_index;
    DCHECK(decoder_thread_task_runner_->BelongsToCurrentThread());
  
    // It's possible that while waiting for the EGLImages to be allocated and
    // assigned, we have already decoded more of the stream and saw another
    // resolution change. This is a normal situation, in such a case either there
    // is no output record with this index awaiting an EGLImage to be assigned to
    // it, or the record is already updated to use a newer PictureBuffer and is
    // awaiting an EGLImage associated with a different picture_buffer_id. If so,
    // just discard this image, we will get the one we are waiting for later.
    if (buffer_index >= output_buffer_map_.size() ||
        output_buffer_map_[buffer_index].picture_id != picture_buffer_id) {
      DVLOGF(3) << "Picture set already changed, dropping EGLImage";
      child_task_runner_->PostTask(
          FROM_HERE, base::Bind(base::IgnoreResult(&V4L2Device::DestroyEGLImage),
                                device_, egl_display_, egl_image));
      return;
    }
  
    OutputRecord& output_record = output_buffer_map_[buffer_index];
    DCHECK_EQ(output_record.egl_image, EGL_NO_IMAGE_KHR);
    DCHECK_EQ(output_record.egl_sync, EGL_NO_SYNC_KHR);
    DCHECK(!output_record.at_client);
    DCHECK(!output_record.at_device);
  
    output_record.egl_image = egl_image;
    if (output_mode_ == Config::OutputMode::IMPORT) {
      DCHECK(output_record.dmabuf_fds.empty());
      output_record.dmabuf_fds = std::move(*passed_dmabuf_fds);
    }
  
    DCHECK_EQ(std::count(free_output_buffers_.begin(), free_output_buffers_.end(),
                         buffer_index),
              0);
    free_output_buffers_.push_back(buffer_index);
    ScheduleDecodeBufferTaskIfNeeded();
  }
  
  void V4L2SliceVideoDecodeAccelerator::ImportBufferForPicture(
      int32_t picture_buffer_id,
      const std::vector<gfx::GpuMemoryBufferHandle>& gpu_memory_buffer_handles) {
    DVLOGF(3) << "picture_buffer_id=" << picture_buffer_id;
    DCHECK(child_task_runner_->BelongsToCurrentThread());
  
    auto passed_dmabuf_fds(base::WrapUnique(new std::vector<base::ScopedFD>()));
  #if defined(USE_OZONE)
    for (const auto& handle : gpu_memory_buffer_handles) {
      int fd = -1;
      fd = handle.native_pixmap_handle.fd.fd;
      DCHECK_NE(fd, -1);
      passed_dmabuf_fds->push_back(base::ScopedFD(fd));
    }
  #endif
  
    if (output_mode_ != Config::OutputMode::IMPORT) {
      LOGF(ERROR) << "Cannot import in non-import mode";
      NOTIFY_ERROR(INVALID_ARGUMENT);
      return;
    }
  
    decoder_thread_task_runner_->PostTask(
        FROM_HERE,
        base::Bind(&V4L2SliceVideoDecodeAccelerator::ImportBufferForPictureTask,
                   base::Unretained(this), picture_buffer_id,
                   base::Passed(&passed_dmabuf_fds)));
  }
  
  void V4L2SliceVideoDecodeAccelerator::ImportBufferForPictureTask(
      int32_t picture_buffer_id,
      std::unique_ptr<std::vector<base::ScopedFD>> passed_dmabuf_fds) {
    DVLOGF(3) << "picture_buffer_id=" << picture_buffer_id;
    DCHECK(decoder_thread_task_runner_->BelongsToCurrentThread());
  
    const auto iter =
        std::find_if(output_buffer_map_.begin(), output_buffer_map_.end(),
                     [picture_buffer_id](const OutputRecord& output_record) {
                       return output_record.picture_id == picture_buffer_id;
                     });
    if (iter == output_buffer_map_.end()) {
      LOGF(ERROR) << "Invalid picture_buffer_id=" << picture_buffer_id;
      NOTIFY_ERROR(INVALID_ARGUMENT);
      return;
    }
  
    if (!iter->at_client) {
      LOGF(ERROR) << "Cannot import buffer that not owned by client";
      NOTIFY_ERROR(INVALID_ARGUMENT);
      return;
    }
  
    size_t index = iter - output_buffer_map_.begin();
    DCHECK_EQ(std::count(free_output_buffers_.begin(), free_output_buffers_.end(),
                         index),
              0);
  
    DCHECK(!iter->at_device);
    iter->at_client = false;
    if (iter->texture_id != 0) {
      if (iter->egl_image != EGL_NO_IMAGE_KHR) {
        child_task_runner_->PostTask(
            FROM_HERE,
            base::Bind(base::IgnoreResult(&V4L2Device::DestroyEGLImage), device_,
                       egl_display_, iter->egl_image));
      }
  
      child_task_runner_->PostTask(
          FROM_HERE,
          base::Bind(&V4L2SliceVideoDecodeAccelerator::CreateEGLImageFor,
                     weak_this_, index, picture_buffer_id,
                     base::Passed(&passed_dmabuf_fds), iter->texture_id,
                     coded_size_, output_format_fourcc_));
    } else {
      // No need for an EGLImage, start using this buffer now.
      DCHECK_EQ(output_planes_count_, passed_dmabuf_fds->size());
      iter->dmabuf_fds.swap(*passed_dmabuf_fds);
      free_output_buffers_.push_back(index);
      ScheduleDecodeBufferTaskIfNeeded();
    }
  }
  
  void V4L2SliceVideoDecodeAccelerator::ReusePictureBuffer(
      int32_t picture_buffer_id) {
    DCHECK(child_task_runner_->BelongsToCurrentThread());
    DVLOGF(4) << "picture_buffer_id=" << picture_buffer_id;
  
    std::unique_ptr<EGLSyncKHRRef> egl_sync_ref;
  
    if (!make_context_current_cb_.is_null()) {
      if (!make_context_current_cb_.Run()) {
        LOGF(ERROR) << "could not make context current";
        NOTIFY_ERROR(PLATFORM_FAILURE);
        return;
      }
  
      EGLSyncKHR egl_sync =
          eglCreateSyncKHR(egl_display_, EGL_SYNC_FENCE_KHR, NULL);
      if (egl_sync == EGL_NO_SYNC_KHR) {
        LOGF(ERROR) << "eglCreateSyncKHR() failed";
        NOTIFY_ERROR(PLATFORM_FAILURE);
        return;
      }
  
      egl_sync_ref.reset(new EGLSyncKHRRef(egl_display_, egl_sync));
    }
  
    decoder_thread_task_runner_->PostTask(
        FROM_HERE,
        base::Bind(&V4L2SliceVideoDecodeAccelerator::ReusePictureBufferTask,
                   base::Unretained(this), picture_buffer_id,
                   base::Passed(&egl_sync_ref)));
  }
  
  void V4L2SliceVideoDecodeAccelerator::ReusePictureBufferTask(
      int32_t picture_buffer_id,
      std::unique_ptr<EGLSyncKHRRef> egl_sync_ref) {
    DVLOGF(3) << "picture_buffer_id=" << picture_buffer_id;
    DCHECK(decoder_thread_task_runner_->BelongsToCurrentThread());
  
    V4L2DecodeSurfaceByPictureBufferId::iterator it =
        surfaces_at_display_.find(picture_buffer_id);
    if (it == surfaces_at_display_.end()) {
      // It's possible that we've already posted a DismissPictureBuffer for this
      // picture, but it has not yet executed when this ReusePictureBuffer was
      // posted to us by the client. In that case just ignore this (we've already
      // dismissed it and accounted for that) and let the sync object get
      // destroyed.
      DVLOGF(3) << "got picture id=" << picture_buffer_id
                << " not in use (anymore?).";
      return;
    }
  
    OutputRecord& output_record = output_buffer_map_[it->second->output_record()];
    if (output_record.at_device || !output_record.at_client) {
      DVLOGF(1) << "picture_buffer_id not reusable";
      NOTIFY_ERROR(INVALID_ARGUMENT);
      return;
    }
  
    DCHECK_EQ(output_record.egl_sync, EGL_NO_SYNC_KHR);
    DCHECK(!output_record.at_device);
    output_record.at_client = false;
    if (egl_sync_ref) {
      output_record.egl_sync = egl_sync_ref->egl_sync;
      // Take ownership of the EGLSync.
      egl_sync_ref->egl_sync = EGL_NO_SYNC_KHR;
    }
  
    surfaces_at_display_.erase(it);
  }
  
  void V4L2SliceVideoDecodeAccelerator::Flush() {
    DVLOGF(3);
    DCHECK(child_task_runner_->BelongsToCurrentThread());
  
    decoder_thread_task_runner_->PostTask(
        FROM_HERE, base::Bind(&V4L2SliceVideoDecodeAccelerator::FlushTask,
                              base::Unretained(this)));
  }
  
  void V4L2SliceVideoDecodeAccelerator::FlushTask() {
    DVLOGF(3);
    DCHECK(decoder_thread_task_runner_->BelongsToCurrentThread());
  
    if (!decoder_input_queue_.empty()) {
      // We are not done with pending inputs, so queue an empty buffer,
      // which - when reached - will trigger flush sequence.
      decoder_input_queue_.push(
          linked_ptr<BitstreamBufferRef>(new BitstreamBufferRef(
              decode_client_, decode_task_runner_, nullptr, kFlushBufferId)));
      return;
    }
  
    // No more inputs pending, so just finish flushing here.
    InitiateFlush();
  }
  
  void V4L2SliceVideoDecodeAccelerator::InitiateFlush() {
    DVLOGF(3);
    DCHECK(decoder_thread_task_runner_->BelongsToCurrentThread());
  
    // This will trigger output for all remaining surfaces in the decoder.
    // However, not all of them may be decoded yet (they would be queued
    // in hardware then).
    if (!decoder_->Flush()) {
      DVLOGF(1) << "Failed flushing the decoder.";
      NOTIFY_ERROR(PLATFORM_FAILURE);
      return;
    }
  
    // Put the decoder in an idle state, ready to resume.
    decoder_->Reset();
  
    DCHECK(!decoder_flushing_);
    decoder_flushing_ = true;
    NewEventPending();
  }
  
  bool V4L2SliceVideoDecodeAccelerator::FinishFlush() {
    DVLOGF(3);
    DCHECK(decoder_thread_task_runner_->BelongsToCurrentThread());
  
    if (!decoder_flushing_)
      return true;
  
    if (!surfaces_at_device_.empty())
      return false;
  
    DCHECK_EQ(state_, kIdle);
  
    // At this point, all remaining surfaces are decoded and dequeued, and since
    // we have already scheduled output for them in InitiateFlush(), their
    // respective PictureReady calls have been posted (or they have been queued on
    // pending_picture_ready_). So at this time, once we SendPictureReady(),
    // we will have all remaining PictureReady() posted to the client and we
    // can post NotifyFlushDone().
    DCHECK(decoder_display_queue_.empty());
  
    // Decoder should have already returned all surfaces and all surfaces are
    // out of hardware. There can be no other owners of input buffers.
    DCHECK_EQ(free_input_buffers_.size(), input_buffer_map_.size());
  
    SendPictureReady();
  
    decoder_flushing_ = false;
    DVLOGF(3) << "Flush finished";
  
    child_task_runner_->PostTask(FROM_HERE,
                                 base::Bind(&Client::NotifyFlushDone, client_));
  
    return true;
  }
  
  void V4L2SliceVideoDecodeAccelerator::Reset() {
    DVLOGF(3);
    DCHECK(child_task_runner_->BelongsToCurrentThread());
  
    decoder_thread_task_runner_->PostTask(
        FROM_HERE, base::Bind(&V4L2SliceVideoDecodeAccelerator::ResetTask,
                              base::Unretained(this)));
  }
  
  void V4L2SliceVideoDecodeAccelerator::ResetTask() {
    DVLOGF(3);
    DCHECK(decoder_thread_task_runner_->BelongsToCurrentThread());
  
    if (decoder_resetting_) {
      // This is a bug in the client, multiple Reset()s before NotifyResetDone()
      // are not allowed.
      NOTREACHED() << "Client should not be requesting multiple Reset()s";
      return;
    }
  
    // Put the decoder in an idle state, ready to resume.
    decoder_->Reset();
  
    // Drop all remaining inputs.
    decoder_current_bitstream_buffer_.reset();
    while (!decoder_input_queue_.empty())
      decoder_input_queue_.pop();
  
    decoder_resetting_ = true;
    NewEventPending();
  }
  
  bool V4L2SliceVideoDecodeAccelerator::FinishReset() {
    DVLOGF(3);
    DCHECK(decoder_thread_task_runner_->BelongsToCurrentThread());
  
    if (!decoder_resetting_)
      return true;
  
    if (!surfaces_at_device_.empty())
      return false;
  
    DCHECK_EQ(state_, kIdle);
    DCHECK(!decoder_flushing_);
    SendPictureReady();
  
    // Drop any pending outputs.
    while (!decoder_display_queue_.empty())
      decoder_display_queue_.pop();
  
    // At this point we can have no input buffers in the decoder, because we
    // Reset()ed it in ResetTask(), and have not scheduled any new Decode()s
    // having been in kIdle since. We don't have any surfaces in the HW either -
    // we just checked that surfaces_at_device_.empty(), and inputs are tied
    // to surfaces. Since there can be no other owners of input buffers, we can
    // simply mark them all as available.
    DCHECK_EQ(input_buffer_queued_count_, 0);
    free_input_buffers_.clear();
    for (size_t i = 0; i < input_buffer_map_.size(); ++i) {
      DCHECK(!input_buffer_map_[i].at_device);
      ReuseInputBuffer(i);
    }
  
    decoder_resetting_ = false;
    DVLOGF(3) << "Reset finished";
  
    child_task_runner_->PostTask(FROM_HERE,
                                 base::Bind(&Client::NotifyResetDone, client_));
  
    return true;
  }
  
  void V4L2SliceVideoDecodeAccelerator::SetErrorState(Error error) {
    // We can touch decoder_state_ only if this is the decoder thread or the
    // decoder thread isn't running.
    if (decoder_thread_.IsRunning() &&
        !decoder_thread_task_runner_->BelongsToCurrentThread()) {
      decoder_thread_task_runner_->PostTask(
          FROM_HERE, base::Bind(&V4L2SliceVideoDecodeAccelerator::SetErrorState,
                                base::Unretained(this), error));
      return;
    }
  
    // Post NotifyError only if we are already initialized, as the API does
    // not allow doing so before that.
    if (state_ != kError && state_ != kUninitialized)
      NotifyError(error);
  
    state_ = kError;
  }
  
  V4L2SliceVideoDecodeAccelerator::V4L2H264Accelerator::V4L2H264Accelerator(
      V4L2SliceVideoDecodeAccelerator* v4l2_dec)
      : num_slices_(0), v4l2_dec_(v4l2_dec) {
    DCHECK(v4l2_dec_);
  }
  
  V4L2SliceVideoDecodeAccelerator::V4L2H264Accelerator::~V4L2H264Accelerator() {}
  
  scoped_refptr<H264Picture>
  V4L2SliceVideoDecodeAccelerator::V4L2H264Accelerator::CreateH264Picture() {
    scoped_refptr<V4L2DecodeSurface> dec_surface = v4l2_dec_->CreateSurface();
    if (!dec_surface)
      return nullptr;
  
    return new V4L2H264Picture(dec_surface);
  }
  
  void V4L2SliceVideoDecodeAccelerator::V4L2H264Accelerator::
      H264PictureListToDPBIndicesList(const H264Picture::Vector& src_pic_list,
                                      uint8_t dst_list[kDPBIndicesListSize]) {
    size_t i;
    for (i = 0; i < src_pic_list.size() && i < kDPBIndicesListSize; ++i) {
      const scoped_refptr<H264Picture>& pic = src_pic_list[i];
      dst_list[i] = pic ? pic->dpb_position : VIDEO_MAX_FRAME;
    }
  
    while (i < kDPBIndicesListSize)
      dst_list[i++] = VIDEO_MAX_FRAME;
  }
  
  void V4L2SliceVideoDecodeAccelerator::V4L2H264Accelerator::H264DPBToV4L2DPB(
      const H264DPB& dpb,
      std::vector<scoped_refptr<V4L2DecodeSurface>>* ref_surfaces) {
    memset(v4l2_decode_param_.dpb, 0, sizeof(v4l2_decode_param_.dpb));
    size_t i = 0;
    for (const auto& pic : dpb) {
      if (i >= arraysize(v4l2_decode_param_.dpb)) {
        DVLOG(1) << "Invalid DPB size";
        break;
      }
  
      int index = VIDEO_MAX_FRAME;
      if (!pic->nonexisting) {
        scoped_refptr<V4L2DecodeSurface> dec_surface =
            H264PictureToV4L2DecodeSurface(pic);
        index = dec_surface->output_record();
        ref_surfaces->push_back(dec_surface);
      }
  
      struct v4l2_h264_dpb_entry& entry = v4l2_decode_param_.dpb[i++];
      entry.buf_index = index;
      entry.frame_num = pic->frame_num;
      entry.pic_num = pic->pic_num;
      entry.top_field_order_cnt = pic->top_field_order_cnt;
      entry.bottom_field_order_cnt = pic->bottom_field_order_cnt;
      entry.flags = (pic->ref ? V4L2_H264_DPB_ENTRY_FLAG_ACTIVE : 0) |
                    (pic->long_term ? V4L2_H264_DPB_ENTRY_FLAG_LONG_TERM : 0);
    }
  }
  
  bool V4L2SliceVideoDecodeAccelerator::V4L2H264Accelerator::SubmitFrameMetadata(
      const media::H264SPS* sps,
      const media::H264PPS* pps,
      const H264DPB& dpb,
      const H264Picture::Vector& ref_pic_listp0,
      const H264Picture::Vector& ref_pic_listb0,
      const H264Picture::Vector& ref_pic_listb1,
      const scoped_refptr<H264Picture>& pic) {
    struct v4l2_ext_control ctrl;
    std::vector<struct v4l2_ext_control> ctrls;
  
    struct v4l2_ctrl_h264_sps v4l2_sps;
    memset(&v4l2_sps, 0, sizeof(v4l2_sps));
    v4l2_sps.constraint_set_flags =
        (sps->constraint_set0_flag ? V4L2_H264_SPS_CONSTRAINT_SET0_FLAG : 0) |
        (sps->constraint_set1_flag ? V4L2_H264_SPS_CONSTRAINT_SET1_FLAG : 0) |
        (sps->constraint_set2_flag ? V4L2_H264_SPS_CONSTRAINT_SET2_FLAG : 0) |
        (sps->constraint_set3_flag ? V4L2_H264_SPS_CONSTRAINT_SET3_FLAG : 0) |
        (sps->constraint_set4_flag ? V4L2_H264_SPS_CONSTRAINT_SET4_FLAG : 0) |
        (sps->constraint_set5_flag ? V4L2_H264_SPS_CONSTRAINT_SET5_FLAG : 0);
  #define SPS_TO_V4L2SPS(a) v4l2_sps.a = sps->a
    SPS_TO_V4L2SPS(profile_idc);
    SPS_TO_V4L2SPS(level_idc);
    SPS_TO_V4L2SPS(seq_parameter_set_id);
    SPS_TO_V4L2SPS(chroma_format_idc);
    SPS_TO_V4L2SPS(bit_depth_luma_minus8);
    SPS_TO_V4L2SPS(bit_depth_chroma_minus8);
    SPS_TO_V4L2SPS(log2_max_frame_num_minus4);
    SPS_TO_V4L2SPS(pic_order_cnt_type);
    SPS_TO_V4L2SPS(log2_max_pic_order_cnt_lsb_minus4);
    SPS_TO_V4L2SPS(offset_for_non_ref_pic);
    SPS_TO_V4L2SPS(offset_for_top_to_bottom_field);
    SPS_TO_V4L2SPS(num_ref_frames_in_pic_order_cnt_cycle);
  
    static_assert(arraysize(v4l2_sps.offset_for_ref_frame) ==
                      arraysize(sps->offset_for_ref_frame),
                  "offset_for_ref_frame arrays must be same size");
    for (size_t i = 0; i < arraysize(v4l2_sps.offset_for_ref_frame); ++i)
      v4l2_sps.offset_for_ref_frame[i] = sps->offset_for_ref_frame[i];
    SPS_TO_V4L2SPS(max_num_ref_frames);
    SPS_TO_V4L2SPS(pic_width_in_mbs_minus1);
    SPS_TO_V4L2SPS(pic_height_in_map_units_minus1);
  #undef SPS_TO_V4L2SPS
  
  #define SET_V4L2_SPS_FLAG_IF(cond, flag) \
    v4l2_sps.flags |= ((sps->cond) ? (flag) : 0)
    SET_V4L2_SPS_FLAG_IF(separate_colour_plane_flag,
                         V4L2_H264_SPS_FLAG_SEPARATE_COLOUR_PLANE);
    SET_V4L2_SPS_FLAG_IF(qpprime_y_zero_transform_bypass_flag,
                         V4L2_H264_SPS_FLAG_QPPRIME_Y_ZERO_TRANSFORM_BYPASS);
    SET_V4L2_SPS_FLAG_IF(delta_pic_order_always_zero_flag,
                         V4L2_H264_SPS_FLAG_DELTA_PIC_ORDER_ALWAYS_ZERO);
    SET_V4L2_SPS_FLAG_IF(gaps_in_frame_num_value_allowed_flag,
                         V4L2_H264_SPS_FLAG_GAPS_IN_FRAME_NUM_VALUE_ALLOWED);
    SET_V4L2_SPS_FLAG_IF(frame_mbs_only_flag, V4L2_H264_SPS_FLAG_FRAME_MBS_ONLY);
    SET_V4L2_SPS_FLAG_IF(mb_adaptive_frame_field_flag,
                         V4L2_H264_SPS_FLAG_MB_ADAPTIVE_FRAME_FIELD);
    SET_V4L2_SPS_FLAG_IF(direct_8x8_inference_flag,
                         V4L2_H264_SPS_FLAG_DIRECT_8X8_INFERENCE);
  #undef SET_FLAG
    memset(&ctrl, 0, sizeof(ctrl));
    ctrl.id = V4L2_CID_MPEG_VIDEO_H264_SPS;
    ctrl.size = sizeof(v4l2_sps);
    ctrl.p_h264_sps = &v4l2_sps;
    ctrls.push_back(ctrl);
  
    struct v4l2_ctrl_h264_pps v4l2_pps;
    memset(&v4l2_pps, 0, sizeof(v4l2_pps));
  #define PPS_TO_V4L2PPS(a) v4l2_pps.a = pps->a
    PPS_TO_V4L2PPS(pic_parameter_set_id);
    PPS_TO_V4L2PPS(seq_parameter_set_id);
    PPS_TO_V4L2PPS(num_slice_groups_minus1);
    PPS_TO_V4L2PPS(num_ref_idx_l0_default_active_minus1);
    PPS_TO_V4L2PPS(num_ref_idx_l1_default_active_minus1);
    PPS_TO_V4L2PPS(weighted_bipred_idc);
    PPS_TO_V4L2PPS(pic_init_qp_minus26);
    PPS_TO_V4L2PPS(pic_init_qs_minus26);
    PPS_TO_V4L2PPS(chroma_qp_index_offset);
    PPS_TO_V4L2PPS(second_chroma_qp_index_offset);
  #undef PPS_TO_V4L2PPS
  
  #define SET_V4L2_PPS_FLAG_IF(cond, flag) \
    v4l2_pps.flags |= ((pps->cond) ? (flag) : 0)
    SET_V4L2_PPS_FLAG_IF(entropy_coding_mode_flag,
                         V4L2_H264_PPS_FLAG_ENTROPY_CODING_MODE);
    SET_V4L2_PPS_FLAG_IF(
        bottom_field_pic_order_in_frame_present_flag,
        V4L2_H264_PPS_FLAG_BOTTOM_FIELD_PIC_ORDER_IN_FRAME_PRESENT);
    SET_V4L2_PPS_FLAG_IF(weighted_pred_flag, V4L2_H264_PPS_FLAG_WEIGHTED_PRED);
    SET_V4L2_PPS_FLAG_IF(deblocking_filter_control_present_flag,
                         V4L2_H264_PPS_FLAG_DEBLOCKING_FILTER_CONTROL_PRESENT);
    SET_V4L2_PPS_FLAG_IF(constrained_intra_pred_flag,
                         V4L2_H264_PPS_FLAG_CONSTRAINED_INTRA_PRED);
    SET_V4L2_PPS_FLAG_IF(redundant_pic_cnt_present_flag,
                         V4L2_H264_PPS_FLAG_REDUNDANT_PIC_CNT_PRESENT);
    SET_V4L2_PPS_FLAG_IF(transform_8x8_mode_flag,
                         V4L2_H264_PPS_FLAG_TRANSFORM_8X8_MODE);
    SET_V4L2_PPS_FLAG_IF(pic_scaling_matrix_present_flag,
                         V4L2_H264_PPS_FLAG_PIC_SCALING_MATRIX_PRESENT);
  #undef SET_V4L2_PPS_FLAG_IF
    memset(&ctrl, 0, sizeof(ctrl));
    ctrl.id = V4L2_CID_MPEG_VIDEO_H264_PPS;
    ctrl.size = sizeof(v4l2_pps);
    ctrl.p_h264_pps = &v4l2_pps;
    ctrls.push_back(ctrl);
  
    struct v4l2_ctrl_h264_scaling_matrix v4l2_scaling_matrix;
    memset(&v4l2_scaling_matrix, 0, sizeof(v4l2_scaling_matrix));
    static_assert(arraysize(v4l2_scaling_matrix.scaling_list_4x4) <=
                          arraysize(pps->scaling_list4x4) &&
                      arraysize(v4l2_scaling_matrix.scaling_list_4x4[0]) <=
                          arraysize(pps->scaling_list4x4[0]) &&
                      arraysize(v4l2_scaling_matrix.scaling_list_8x8) <=
                          arraysize(pps->scaling_list8x8) &&
                      arraysize(v4l2_scaling_matrix.scaling_list_8x8[0]) <=
                          arraysize(pps->scaling_list8x8[0]),
                  "scaling_lists must be of correct size");
    for (size_t i = 0; i < arraysize(v4l2_scaling_matrix.scaling_list_4x4); ++i) {
      for (size_t j = 0; j < arraysize(v4l2_scaling_matrix.scaling_list_4x4[i]);
           ++j) {
        v4l2_scaling_matrix.scaling_list_4x4[i][j] = pps->scaling_list4x4[i][j];
      }
    }
    for (size_t i = 0; i < arraysize(v4l2_scaling_matrix.scaling_list_8x8); ++i) {
      for (size_t j = 0; j < arraysize(v4l2_scaling_matrix.scaling_list_8x8[i]);
           ++j) {
        v4l2_scaling_matrix.scaling_list_8x8[i][j] = pps->scaling_list8x8[i][j];
      }
    }
    memset(&ctrl, 0, sizeof(ctrl));
    ctrl.id = V4L2_CID_MPEG_VIDEO_H264_SCALING_MATRIX;
    ctrl.size = sizeof(v4l2_scaling_matrix);
    ctrl.p_h264_scal_mtrx = &v4l2_scaling_matrix;
    ctrls.push_back(ctrl);
  
    scoped_refptr<V4L2DecodeSurface> dec_surface =
        H264PictureToV4L2DecodeSurface(pic);
  
    struct v4l2_ext_controls ext_ctrls;
    memset(&ext_ctrls, 0, sizeof(ext_ctrls));
    ext_ctrls.count = ctrls.size();
    ext_ctrls.controls = &ctrls[0];
    ext_ctrls.config_store = dec_surface->config_store();
    v4l2_dec_->SubmitExtControls(&ext_ctrls);
  
    H264PictureListToDPBIndicesList(ref_pic_listp0,
                                    v4l2_decode_param_.ref_pic_list_p0);
    H264PictureListToDPBIndicesList(ref_pic_listb0,
                                    v4l2_decode_param_.ref_pic_list_b0);
    H264PictureListToDPBIndicesList(ref_pic_listb1,
                                    v4l2_decode_param_.ref_pic_list_b1);
  
    std::vector<scoped_refptr<V4L2DecodeSurface>> ref_surfaces;
    H264DPBToV4L2DPB(dpb, &ref_surfaces);
    dec_surface->SetReferenceSurfaces(ref_surfaces);
  
    return true;
  }
  
  bool V4L2SliceVideoDecodeAccelerator::V4L2H264Accelerator::SubmitSlice(
      const media::H264PPS* pps,
      const media::H264SliceHeader* slice_hdr,
      const H264Picture::Vector& ref_pic_list0,
      const H264Picture::Vector& ref_pic_list1,
      const scoped_refptr<H264Picture>& pic,
      const uint8_t* data,
      size_t size) {
    if (num_slices_ == kMaxSlices) {
      LOGF(ERROR) << "Over limit of supported slices per frame";
      return false;
    }
  
    struct v4l2_ctrl_h264_slice_param& v4l2_slice_param =
        v4l2_slice_params_[num_slices_++];
    memset(&v4l2_slice_param, 0, sizeof(v4l2_slice_param));
  
    v4l2_slice_param.size = size;
  #define SHDR_TO_V4L2SPARM(a) v4l2_slice_param.a = slice_hdr->a
    SHDR_TO_V4L2SPARM(header_bit_size);
    SHDR_TO_V4L2SPARM(first_mb_in_slice);
    SHDR_TO_V4L2SPARM(slice_type);
    SHDR_TO_V4L2SPARM(pic_parameter_set_id);
    SHDR_TO_V4L2SPARM(colour_plane_id);
    SHDR_TO_V4L2SPARM(frame_num);
    SHDR_TO_V4L2SPARM(idr_pic_id);
    SHDR_TO_V4L2SPARM(pic_order_cnt_lsb);
    SHDR_TO_V4L2SPARM(delta_pic_order_cnt_bottom);
    SHDR_TO_V4L2SPARM(delta_pic_order_cnt0);
    SHDR_TO_V4L2SPARM(delta_pic_order_cnt1);
    SHDR_TO_V4L2SPARM(redundant_pic_cnt);
    SHDR_TO_V4L2SPARM(dec_ref_pic_marking_bit_size);
    SHDR_TO_V4L2SPARM(cabac_init_idc);
    SHDR_TO_V4L2SPARM(slice_qp_delta);
    SHDR_TO_V4L2SPARM(slice_qs_delta);
    SHDR_TO_V4L2SPARM(disable_deblocking_filter_idc);
    SHDR_TO_V4L2SPARM(slice_alpha_c0_offset_div2);
    SHDR_TO_V4L2SPARM(slice_beta_offset_div2);
    SHDR_TO_V4L2SPARM(num_ref_idx_l0_active_minus1);
    SHDR_TO_V4L2SPARM(num_ref_idx_l1_active_minus1);
    SHDR_TO_V4L2SPARM(pic_order_cnt_bit_size);
  #undef SHDR_TO_V4L2SPARM
  
  #define SET_V4L2_SPARM_FLAG_IF(cond, flag) \
    v4l2_slice_param.flags |= ((slice_hdr->cond) ? (flag) : 0)
    SET_V4L2_SPARM_FLAG_IF(field_pic_flag, V4L2_SLICE_FLAG_FIELD_PIC);
    SET_V4L2_SPARM_FLAG_IF(bottom_field_flag, V4L2_SLICE_FLAG_BOTTOM_FIELD);
    SET_V4L2_SPARM_FLAG_IF(direct_spatial_mv_pred_flag,
                           V4L2_SLICE_FLAG_DIRECT_SPATIAL_MV_PRED);
    SET_V4L2_SPARM_FLAG_IF(sp_for_switch_flag, V4L2_SLICE_FLAG_SP_FOR_SWITCH);
  #undef SET_V4L2_SPARM_FLAG_IF
  
    struct v4l2_h264_pred_weight_table* pred_weight_table =
        &v4l2_slice_param.pred_weight_table;
  
    if (((slice_hdr->IsPSlice() || slice_hdr->IsSPSlice()) &&
         pps->weighted_pred_flag) ||
        (slice_hdr->IsBSlice() && pps->weighted_bipred_idc == 1)) {
      pred_weight_table->luma_log2_weight_denom =
          slice_hdr->luma_log2_weight_denom;
      pred_weight_table->chroma_log2_weight_denom =
          slice_hdr->chroma_log2_weight_denom;
  
      struct v4l2_h264_weight_factors* factorsl0 =
          &pred_weight_table->weight_factors[0];
  
      for (int i = 0; i < 32; ++i) {
        factorsl0->luma_weight[i] =
            slice_hdr->pred_weight_table_l0.luma_weight[i];
        factorsl0->luma_offset[i] =
            slice_hdr->pred_weight_table_l0.luma_offset[i];
  
        for (int j = 0; j < 2; ++j) {
          factorsl0->chroma_weight[i][j] =
              slice_hdr->pred_weight_table_l0.chroma_weight[i][j];
          factorsl0->chroma_offset[i][j] =
              slice_hdr->pred_weight_table_l0.chroma_offset[i][j];
        }
      }
  
      if (slice_hdr->IsBSlice()) {
        struct v4l2_h264_weight_factors* factorsl1 =
            &pred_weight_table->weight_factors[1];
  
        for (int i = 0; i < 32; ++i) {
          factorsl1->luma_weight[i] =
              slice_hdr->pred_weight_table_l1.luma_weight[i];
          factorsl1->luma_offset[i] =
              slice_hdr->pred_weight_table_l1.luma_offset[i];
  
          for (int j = 0; j < 2; ++j) {
            factorsl1->chroma_weight[i][j] =
                slice_hdr->pred_weight_table_l1.chroma_weight[i][j];
            factorsl1->chroma_offset[i][j] =
                slice_hdr->pred_weight_table_l1.chroma_offset[i][j];
          }
        }
      }
    }
  
    H264PictureListToDPBIndicesList(ref_pic_list0,
                                    v4l2_slice_param.ref_pic_list0);
    H264PictureListToDPBIndicesList(ref_pic_list1,
                                    v4l2_slice_param.ref_pic_list1);
  
    scoped_refptr<V4L2DecodeSurface> dec_surface =
        H264PictureToV4L2DecodeSurface(pic);
  
    v4l2_decode_param_.nal_ref_idc = slice_hdr->nal_ref_idc;
  
    // TODO(posciak): Don't add start code back here, but have it passed from
    // the parser.
    size_t data_copy_size = size + 3;
    std::unique_ptr<uint8_t[]> data_copy(new uint8_t[data_copy_size]);
    memset(data_copy.get(), 0, data_copy_size);
    data_copy[2] = 0x01;
    memcpy(data_copy.get() + 3, data, size);
    return v4l2_dec_->SubmitSlice(dec_surface->input_record(), data_copy.get(),
                                  data_copy_size);
  }
  
  bool V4L2SliceVideoDecodeAccelerator::SubmitSlice(int index,
                                                    const uint8_t* data,
                                                    size_t size) {
    DCHECK(decoder_thread_task_runner_->BelongsToCurrentThread());
  
    InputRecord& input_record = input_buffer_map_[index];
  
    if (input_record.bytes_used + size > input_record.length) {
      DVLOGF(1) << "Input buffer too small";
      return false;
    }
  
    memcpy(static_cast<uint8_t*>(input_record.address) + input_record.bytes_used,
           data, size);
    input_record.bytes_used += size;
  
    return true;
  }
  
  bool V4L2SliceVideoDecodeAccelerator::SubmitExtControls(
      struct v4l2_ext_controls* ext_ctrls) {
    DCHECK_GT(ext_ctrls->config_store, 0u);
    IOCTL_OR_ERROR_RETURN_FALSE(VIDIOC_S_EXT_CTRLS, ext_ctrls);
    return true;
  }
  
  bool V4L2SliceVideoDecodeAccelerator::V4L2H264Accelerator::SubmitDecode(
      const scoped_refptr<H264Picture>& pic) {
    scoped_refptr<V4L2DecodeSurface> dec_surface =
        H264PictureToV4L2DecodeSurface(pic);
  
    v4l2_decode_param_.num_slices = num_slices_;
    v4l2_decode_param_.idr_pic_flag = pic->idr;
    v4l2_decode_param_.top_field_order_cnt = pic->top_field_order_cnt;
    v4l2_decode_param_.bottom_field_order_cnt = pic->bottom_field_order_cnt;
  
    struct v4l2_ext_control ctrl;
    std::vector<struct v4l2_ext_control> ctrls;
  
    memset(&ctrl, 0, sizeof(ctrl));
    ctrl.id = V4L2_CID_MPEG_VIDEO_H264_SLICE_PARAM;
    ctrl.size = sizeof(v4l2_slice_params_);
    ctrl.p_h264_slice_param = v4l2_slice_params_;
    ctrls.push_back(ctrl);
  
    memset(&ctrl, 0, sizeof(ctrl));
    ctrl.id = V4L2_CID_MPEG_VIDEO_H264_DECODE_PARAM;
    ctrl.size = sizeof(v4l2_decode_param_);
    ctrl.p_h264_decode_param = &v4l2_decode_param_;
    ctrls.push_back(ctrl);
  
    struct v4l2_ext_controls ext_ctrls;
    memset(&ext_ctrls, 0, sizeof(ext_ctrls));
    ext_ctrls.count = ctrls.size();
    ext_ctrls.controls = &ctrls[0];
    ext_ctrls.config_store = dec_surface->config_store();
    v4l2_dec_->SubmitExtControls(&ext_ctrls);
  
    Reset();
  
    v4l2_dec_->DecodeSurface(dec_surface);
    return true;
  }
  
  bool V4L2SliceVideoDecodeAccelerator::V4L2H264Accelerator::OutputPicture(
      const scoped_refptr<H264Picture>& pic) {
    scoped_refptr<V4L2DecodeSurface> dec_surface =
        H264PictureToV4L2DecodeSurface(pic);
    v4l2_dec_->SurfaceReady(dec_surface);
    return true;
  }
  
  void V4L2SliceVideoDecodeAccelerator::V4L2H264Accelerator::Reset() {
    num_slices_ = 0;
    memset(&v4l2_decode_param_, 0, sizeof(v4l2_decode_param_));
    memset(&v4l2_slice_params_, 0, sizeof(v4l2_slice_params_));
  }
  
  scoped_refptr<V4L2SliceVideoDecodeAccelerator::V4L2DecodeSurface>
  V4L2SliceVideoDecodeAccelerator::V4L2H264Accelerator::
      H264PictureToV4L2DecodeSurface(const scoped_refptr<H264Picture>& pic) {
    V4L2H264Picture* v4l2_pic = pic->AsV4L2H264Picture();
    CHECK(v4l2_pic);
    return v4l2_pic->dec_surface();
  }
  
  V4L2SliceVideoDecodeAccelerator::V4L2VP8Accelerator::V4L2VP8Accelerator(
      V4L2SliceVideoDecodeAccelerator* v4l2_dec)
      : v4l2_dec_(v4l2_dec) {
    DCHECK(v4l2_dec_);
  }
  
  V4L2SliceVideoDecodeAccelerator::V4L2VP8Accelerator::~V4L2VP8Accelerator() {}
  
  scoped_refptr<VP8Picture>
  V4L2SliceVideoDecodeAccelerator::V4L2VP8Accelerator::CreateVP8Picture() {
    scoped_refptr<V4L2DecodeSurface> dec_surface = v4l2_dec_->CreateSurface();
    if (!dec_surface)
      return nullptr;
  
    return new V4L2VP8Picture(dec_surface);
  }
  
  #define ARRAY_MEMCPY_CHECKED(to, from)                               \
    do {                                                               \
      static_assert(sizeof(to) == sizeof(from),                        \
                    #from " and " #to " arrays must be of same size"); \
      memcpy(to, from, sizeof(to));                                    \
    } while (0)
  
  static void FillV4L2SegmentationHeader(
      const media::Vp8SegmentationHeader& vp8_sgmnt_hdr,
      struct v4l2_vp8_sgmnt_hdr* v4l2_sgmnt_hdr) {
  #define SET_V4L2_SGMNT_HDR_FLAG_IF(cond, flag) \
    v4l2_sgmnt_hdr->flags |= ((vp8_sgmnt_hdr.cond) ? (flag) : 0)
    SET_V4L2_SGMNT_HDR_FLAG_IF(segmentation_enabled,
                               V4L2_VP8_SEGMNT_HDR_FLAG_ENABLED);
    SET_V4L2_SGMNT_HDR_FLAG_IF(update_mb_segmentation_map,
                               V4L2_VP8_SEGMNT_HDR_FLAG_UPDATE_MAP);
    SET_V4L2_SGMNT_HDR_FLAG_IF(update_segment_feature_data,
                               V4L2_VP8_SEGMNT_HDR_FLAG_UPDATE_FEATURE_DATA);
  #undef SET_V4L2_SPARM_FLAG_IF
    v4l2_sgmnt_hdr->segment_feature_mode = vp8_sgmnt_hdr.segment_feature_mode;
  
    ARRAY_MEMCPY_CHECKED(v4l2_sgmnt_hdr->quant_update,
                         vp8_sgmnt_hdr.quantizer_update_value);
    ARRAY_MEMCPY_CHECKED(v4l2_sgmnt_hdr->lf_update,
                         vp8_sgmnt_hdr.lf_update_value);
    ARRAY_MEMCPY_CHECKED(v4l2_sgmnt_hdr->segment_probs,
                         vp8_sgmnt_hdr.segment_prob);
  }
  
  static void FillV4L2LoopfilterHeader(
      const media::Vp8LoopFilterHeader& vp8_loopfilter_hdr,
      struct v4l2_vp8_loopfilter_hdr* v4l2_lf_hdr) {
  #define SET_V4L2_LF_HDR_FLAG_IF(cond, flag) \
    v4l2_lf_hdr->flags |= ((vp8_loopfilter_hdr.cond) ? (flag) : 0)
    SET_V4L2_LF_HDR_FLAG_IF(loop_filter_adj_enable, V4L2_VP8_LF_HDR_ADJ_ENABLE);
    SET_V4L2_LF_HDR_FLAG_IF(mode_ref_lf_delta_update,
                            V4L2_VP8_LF_HDR_DELTA_UPDATE);
  #undef SET_V4L2_SGMNT_HDR_FLAG_IF
  
  #define LF_HDR_TO_V4L2_LF_HDR(a) v4l2_lf_hdr->a = vp8_loopfilter_hdr.a;
    LF_HDR_TO_V4L2_LF_HDR(type);
    LF_HDR_TO_V4L2_LF_HDR(level);
    LF_HDR_TO_V4L2_LF_HDR(sharpness_level);
  #undef LF_HDR_TO_V4L2_LF_HDR
  
    ARRAY_MEMCPY_CHECKED(v4l2_lf_hdr->ref_frm_delta_magnitude,
                         vp8_loopfilter_hdr.ref_frame_delta);
    ARRAY_MEMCPY_CHECKED(v4l2_lf_hdr->mb_mode_delta_magnitude,
                         vp8_loopfilter_hdr.mb_mode_delta);
  }
  
  static void FillV4L2QuantizationHeader(
      const media::Vp8QuantizationHeader& vp8_quant_hdr,
      struct v4l2_vp8_quantization_hdr* v4l2_quant_hdr) {
    v4l2_quant_hdr->y_ac_qi = vp8_quant_hdr.y_ac_qi;
    v4l2_quant_hdr->y_dc_delta = vp8_quant_hdr.y_dc_delta;
    v4l2_quant_hdr->y2_dc_delta = vp8_quant_hdr.y2_dc_delta;
    v4l2_quant_hdr->y2_ac_delta = vp8_quant_hdr.y2_ac_delta;
    v4l2_quant_hdr->uv_dc_delta = vp8_quant_hdr.uv_dc_delta;
    v4l2_quant_hdr->uv_ac_delta = vp8_quant_hdr.uv_ac_delta;
  }
  
  static void FillV4L2EntropyHeader(
      const media::Vp8EntropyHeader& vp8_entropy_hdr,
      struct v4l2_vp8_entropy_hdr* v4l2_entropy_hdr) {
    ARRAY_MEMCPY_CHECKED(v4l2_entropy_hdr->coeff_probs,
                         vp8_entropy_hdr.coeff_probs);
    ARRAY_MEMCPY_CHECKED(v4l2_entropy_hdr->y_mode_probs,
                         vp8_entropy_hdr.y_mode_probs);
    ARRAY_MEMCPY_CHECKED(v4l2_entropy_hdr->uv_mode_probs,
                         vp8_entropy_hdr.uv_mode_probs);
    ARRAY_MEMCPY_CHECKED(v4l2_entropy_hdr->mv_probs, vp8_entropy_hdr.mv_probs);
  }
  
  bool V4L2SliceVideoDecodeAccelerator::V4L2VP8Accelerator::SubmitDecode(
      const scoped_refptr<VP8Picture>& pic,
      const media::Vp8FrameHeader* frame_hdr,
      const scoped_refptr<VP8Picture>& last_frame,
      const scoped_refptr<VP8Picture>& golden_frame,
      const scoped_refptr<VP8Picture>& alt_frame) {
    struct v4l2_ctrl_vp8_frame_hdr v4l2_frame_hdr;
    memset(&v4l2_frame_hdr, 0, sizeof(v4l2_frame_hdr));
  
  #define FHDR_TO_V4L2_FHDR(a) v4l2_frame_hdr.a = frame_hdr->a
    FHDR_TO_V4L2_FHDR(key_frame);
    FHDR_TO_V4L2_FHDR(version);
    FHDR_TO_V4L2_FHDR(width);
    FHDR_TO_V4L2_FHDR(horizontal_scale);
    FHDR_TO_V4L2_FHDR(height);
    FHDR_TO_V4L2_FHDR(vertical_scale);
    FHDR_TO_V4L2_FHDR(sign_bias_golden);
    FHDR_TO_V4L2_FHDR(sign_bias_alternate);
    FHDR_TO_V4L2_FHDR(prob_skip_false);
    FHDR_TO_V4L2_FHDR(prob_intra);
    FHDR_TO_V4L2_FHDR(prob_last);
    FHDR_TO_V4L2_FHDR(prob_gf);
    FHDR_TO_V4L2_FHDR(bool_dec_range);
    FHDR_TO_V4L2_FHDR(bool_dec_value);
    FHDR_TO_V4L2_FHDR(bool_dec_count);
  #undef FHDR_TO_V4L2_FHDR
  
  #define SET_V4L2_FRM_HDR_FLAG_IF(cond, flag) \
    v4l2_frame_hdr.flags |= ((frame_hdr->cond) ? (flag) : 0)
    SET_V4L2_FRM_HDR_FLAG_IF(is_experimental,
                             V4L2_VP8_FRAME_HDR_FLAG_EXPERIMENTAL);
    SET_V4L2_FRM_HDR_FLAG_IF(show_frame, V4L2_VP8_FRAME_HDR_FLAG_SHOW_FRAME);
    SET_V4L2_FRM_HDR_FLAG_IF(mb_no_skip_coeff,
                             V4L2_VP8_FRAME_HDR_FLAG_MB_NO_SKIP_COEFF);
  #undef SET_V4L2_FRM_HDR_FLAG_IF
  
    FillV4L2SegmentationHeader(frame_hdr->segmentation_hdr,
                               &v4l2_frame_hdr.sgmnt_hdr);
  
    FillV4L2LoopfilterHeader(frame_hdr->loopfilter_hdr, &v4l2_frame_hdr.lf_hdr);
  
    FillV4L2QuantizationHeader(frame_hdr->quantization_hdr,
                               &v4l2_frame_hdr.quant_hdr);
  
    FillV4L2EntropyHeader(frame_hdr->entropy_hdr, &v4l2_frame_hdr.entropy_hdr);
  
    v4l2_frame_hdr.first_part_size =
        base::checked_cast<__u32>(frame_hdr->first_part_size);
    v4l2_frame_hdr.first_part_offset =
        base::checked_cast<__u32>(frame_hdr->first_part_offset);
    v4l2_frame_hdr.macroblock_bit_offset =
        base::checked_cast<__u32>(frame_hdr->macroblock_bit_offset);
    v4l2_frame_hdr.num_dct_parts = frame_hdr->num_of_dct_partitions;
  
    static_assert(arraysize(v4l2_frame_hdr.dct_part_sizes) ==
                      arraysize(frame_hdr->dct_partition_sizes),
                  "DCT partition size arrays must have equal number of elements");
    for (size_t i = 0; i < frame_hdr->num_of_dct_partitions &&
                       i < arraysize(v4l2_frame_hdr.dct_part_sizes);
         ++i)
      v4l2_frame_hdr.dct_part_sizes[i] = frame_hdr->dct_partition_sizes[i];
  
    scoped_refptr<V4L2DecodeSurface> dec_surface =
        VP8PictureToV4L2DecodeSurface(pic);
    std::vector<scoped_refptr<V4L2DecodeSurface>> ref_surfaces;
  
    if (last_frame) {
      scoped_refptr<V4L2DecodeSurface> last_frame_surface =
          VP8PictureToV4L2DecodeSurface(last_frame);
      v4l2_frame_hdr.last_frame = last_frame_surface->output_record();
      ref_surfaces.push_back(last_frame_surface);
    } else {
      v4l2_frame_hdr.last_frame = VIDEO_MAX_FRAME;
    }
  
    if (golden_frame) {
      scoped_refptr<V4L2DecodeSurface> golden_frame_surface =
          VP8PictureToV4L2DecodeSurface(golden_frame);
      v4l2_frame_hdr.golden_frame = golden_frame_surface->output_record();
      ref_surfaces.push_back(golden_frame_surface);
    } else {
      v4l2_frame_hdr.golden_frame = VIDEO_MAX_FRAME;
    }
  
    if (alt_frame) {
      scoped_refptr<V4L2DecodeSurface> alt_frame_surface =
          VP8PictureToV4L2DecodeSurface(alt_frame);
      v4l2_frame_hdr.alt_frame = alt_frame_surface->output_record();
      ref_surfaces.push_back(alt_frame_surface);
    } else {
      v4l2_frame_hdr.alt_frame = VIDEO_MAX_FRAME;
    }
  
    struct v4l2_ext_control ctrl;
    memset(&ctrl, 0, sizeof(ctrl));
    ctrl.id = V4L2_CID_MPEG_VIDEO_VP8_FRAME_HDR;
    ctrl.size = sizeof(v4l2_frame_hdr);
    ctrl.p_vp8_frame_hdr = &v4l2_frame_hdr;
  
    struct v4l2_ext_controls ext_ctrls;
    memset(&ext_ctrls, 0, sizeof(ext_ctrls));
    ext_ctrls.count = 1;
    ext_ctrls.controls = &ctrl;
    ext_ctrls.config_store = dec_surface->config_store();
  
    if (!v4l2_dec_->SubmitExtControls(&ext_ctrls))
      return false;
  
    dec_surface->SetReferenceSurfaces(ref_surfaces);
  
    if (!v4l2_dec_->SubmitSlice(dec_surface->input_record(), frame_hdr->data,
                                frame_hdr->frame_size))
      return false;
  
    v4l2_dec_->DecodeSurface(dec_surface);
    return true;
  }
  
  bool V4L2SliceVideoDecodeAccelerator::V4L2VP8Accelerator::OutputPicture(
      const scoped_refptr<VP8Picture>& pic) {
    scoped_refptr<V4L2DecodeSurface> dec_surface =
        VP8PictureToV4L2DecodeSurface(pic);
  
    v4l2_dec_->SurfaceReady(dec_surface);
    return true;
  }
  
  scoped_refptr<V4L2SliceVideoDecodeAccelerator::V4L2DecodeSurface>
  V4L2SliceVideoDecodeAccelerator::V4L2VP8Accelerator::
      VP8PictureToV4L2DecodeSurface(const scoped_refptr<VP8Picture>& pic) {
    V4L2VP8Picture* v4l2_pic = pic->AsV4L2VP8Picture();
    CHECK(v4l2_pic);
    return v4l2_pic->dec_surface();
  }
  
  void V4L2SliceVideoDecodeAccelerator::DecodeSurface(
      const scoped_refptr<V4L2DecodeSurface>& dec_surface) {
    DCHECK(decoder_thread_task_runner_->BelongsToCurrentThread());
  
    DVLOGF(3) << "Submitting decode for surface: " << dec_surface->ToString();
    Enqueue(dec_surface);
  }
  
  void V4L2SliceVideoDecodeAccelerator::SurfaceReady(
      const scoped_refptr<V4L2DecodeSurface>& dec_surface) {
    DVLOGF(3);
    DCHECK(decoder_thread_task_runner_->BelongsToCurrentThread());
  
    decoder_display_queue_.push(dec_surface);
    TryOutputSurfaces();
  }
  
  void V4L2SliceVideoDecodeAccelerator::TryOutputSurfaces() {
    while (!decoder_display_queue_.empty()) {
      scoped_refptr<V4L2DecodeSurface> dec_surface =
          decoder_display_queue_.front();
  
      if (!dec_surface->decoded())
        break;
  
      decoder_display_queue_.pop();
      OutputSurface(dec_surface);
    }
  }
  
  void V4L2SliceVideoDecodeAccelerator::OutputSurface(
      const scoped_refptr<V4L2DecodeSurface>& dec_surface) {
    DCHECK(decoder_thread_task_runner_->BelongsToCurrentThread());
  
    OutputRecord& output_record =
        output_buffer_map_[dec_surface->output_record()];
  
    bool inserted =
        surfaces_at_display_
            .insert(std::make_pair(output_record.picture_id, dec_surface))
            .second;
    DCHECK(inserted);
  
    DCHECK(!output_record.at_client);
    DCHECK(!output_record.at_device);
    DCHECK_NE(output_record.picture_id, -1);
    output_record.at_client = true;
  
    // TODO(posciak): Use visible size from decoder here instead
    // (crbug.com/402760). Passing (0, 0) results in the client using the
    // visible size extracted from the container instead.
    media::Picture picture(output_record.picture_id, dec_surface->bitstream_id(),
                           gfx::Rect(0, 0), false);
    DVLOGF(3) << dec_surface->ToString()
              << ", bitstream_id: " << picture.bitstream_buffer_id()
              << ", picture_id: " << picture.picture_buffer_id();
    pending_picture_ready_.push(PictureRecord(output_record.cleared, picture));
    SendPictureReady();
    output_record.cleared = true;
  }
  
  scoped_refptr<V4L2SliceVideoDecodeAccelerator::V4L2DecodeSurface>
  V4L2SliceVideoDecodeAccelerator::CreateSurface() {
    DCHECK(decoder_thread_task_runner_->BelongsToCurrentThread());
    DCHECK_EQ(state_, kDecoding);
  
    if (free_input_buffers_.empty() || free_output_buffers_.empty())
      return nullptr;
  
    int input = free_input_buffers_.front();
    free_input_buffers_.pop_front();
    int output = free_output_buffers_.front();
    free_output_buffers_.pop_front();
  
    InputRecord& input_record = input_buffer_map_[input];
    DCHECK_EQ(input_record.bytes_used, 0u);
    DCHECK_EQ(input_record.input_id, -1);
    DCHECK(decoder_current_bitstream_buffer_ != nullptr);
    input_record.input_id = decoder_current_bitstream_buffer_->input_id;
  
    scoped_refptr<V4L2DecodeSurface> dec_surface = new V4L2DecodeSurface(
        decoder_current_bitstream_buffer_->input_id, input, output,
        base::Bind(&V4L2SliceVideoDecodeAccelerator::ReuseOutputBuffer,
                   base::Unretained(this)));
  
    DVLOGF(4) << "Created surface " << input << " -> " << output;
    return dec_surface;
  }
  
  void V4L2SliceVideoDecodeAccelerator::SendPictureReady() {
    DVLOGF(3);
    DCHECK(decoder_thread_task_runner_->BelongsToCurrentThread());
    bool resetting_or_flushing = (decoder_resetting_ || decoder_flushing_);
    while (!pending_picture_ready_.empty()) {
      bool cleared = pending_picture_ready_.front().cleared;
      const media::Picture& picture = pending_picture_ready_.front().picture;
      if (cleared && picture_clearing_count_ == 0) {
        DVLOGF(4) << "Posting picture ready to decode task runner for: "
                  << picture.picture_buffer_id();
        // This picture is cleared. It can be posted to a thread different than
        // the main GPU thread to reduce latency. This should be the case after
        // all pictures are cleared at the beginning.
        decode_task_runner_->PostTask(
            FROM_HERE,
            base::Bind(&Client::PictureReady, decode_client_, picture));
        pending_picture_ready_.pop();
      } else if (!cleared || resetting_or_flushing) {
        DVLOGF(3) << "cleared=" << pending_picture_ready_.front().cleared
                  << ", decoder_resetting_=" << decoder_resetting_
                  << ", decoder_flushing_=" << decoder_flushing_
                  << ", picture_clearing_count_=" << picture_clearing_count_;
        DVLOGF(4) << "Posting picture ready to GPU for: "
                  << picture.picture_buffer_id();
        // If the picture is not cleared, post it to the child thread because it
        // has to be cleared in the child thread. A picture only needs to be
        // cleared once. If the decoder is resetting or flushing, send all
        // pictures to ensure PictureReady arrive before reset or flush done.
        child_task_runner_->PostTaskAndReply(
            FROM_HERE, base::Bind(&Client::PictureReady, client_, picture),
            // Unretained is safe. If Client::PictureReady gets to run, |this| is
            // alive. Destroy() will wait the decode thread to finish.
            base::Bind(&V4L2SliceVideoDecodeAccelerator::PictureCleared,
                       base::Unretained(this)));
        picture_clearing_count_++;
        pending_picture_ready_.pop();
      } else {
        // This picture is cleared. But some pictures are about to be cleared on
        // the child thread. To preserve the order, do not send this until those
        // pictures are cleared.
        break;
      }
    }
  }
  
  void V4L2SliceVideoDecodeAccelerator::PictureCleared() {
    DVLOGF(3) << "clearing count=" << picture_clearing_count_;
    DCHECK(decoder_thread_task_runner_->BelongsToCurrentThread());
    DCHECK_GT(picture_clearing_count_, 0);
    picture_clearing_count_--;
    SendPictureReady();
  }
  
  bool V4L2SliceVideoDecodeAccelerator::TryToSetupDecodeOnSeparateThread(
      const base::WeakPtr<Client>& decode_client,
      const scoped_refptr<base::SingleThreadTaskRunner>& decode_task_runner) {
    decode_client_ = decode_client_;
    decode_task_runner_ = decode_task_runner;
    return true;
  }
  
  media::VideoPixelFormat V4L2SliceVideoDecodeAccelerator::GetOutputFormat()
      const {
    return V4L2Device::V4L2PixFmtToVideoPixelFormat(output_format_fourcc_);
  }
  
  // static
  media::VideoDecodeAccelerator::SupportedProfiles
  V4L2SliceVideoDecodeAccelerator::GetSupportedProfiles() {
    scoped_refptr<V4L2Device> device = V4L2Device::Create(V4L2Device::kDecoder);
    if (!device)
      return SupportedProfiles();
  
    return device->GetSupportedDecodeProfiles(arraysize(supported_input_fourccs_),
                                              supported_input_fourccs_);
  }
  
  }  // namespace media
  