text: /*
   * Copyright (c) 2000,2001 Fabrice Bellard
   * Copyright (c) 2006 Luca Abeni
   *
   * This file is part of FFmpeg.
   *
   * FFmpeg is free software; you can redistribute it and/or
   * modify it under the terms of the GNU Lesser General Public
   * License as published by the Free Software Foundation; either
   * version 2.1 of the License, or (at your option) any later version.
   *
   * FFmpeg is distributed in the hope that it will be useful,
   * but WITHOUT ANY WARRANTY; without even the implied warranty of
   * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
   * Lesser General Public License for more details.
   *
   * You should have received a copy of the GNU Lesser General Public
   * License along with FFmpeg; if not, write to the Free Software
   * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
   */
  
  /**
   * @file
   * Video4Linux2 grab interface
   *
   * Part of this file is based on the V4L2 video capture example
   * (http://linuxtv.org/downloads/v4l-dvb-apis/capture-example.html)
   *
   * Thanks to Michael Niedermayer for providing the mapping between
   * V4L2_PIX_FMT_* and AV_PIX_FMT_*
   */
  
  #include "v4l2-common.h"
  #include <dirent.h>
  
  #if CONFIG_LIBV4L2
  #include <libv4l2.h>
  #endif
  
  static const int desired_video_buffers = 256;
  
  #define V4L_ALLFORMATS  3
  #define V4L_RAWFORMATS  1
  #define V4L_COMPFORMATS 2
  
  /**
   * Return timestamps to the user exactly as returned by the kernel
   */
  #define V4L_TS_DEFAULT  0
  /**
   * Autodetect the kind of timestamps returned by the kernel and convert to
   * absolute (wall clock) timestamps.
   */
  #define V4L_TS_ABS      1
  /**
   * Assume kernel timestamps are from the monotonic clock and convert to
   * absolute timestamps.
   */
  #define V4L_TS_MONO2ABS 2
  
  /**
   * Once the kind of timestamps returned by the kernel have been detected,
   * the value of the timefilter (NULL or not) determines whether a conversion
   * takes place.
   */
  #define V4L_TS_CONVERT_READY V4L_TS_DEFAULT
  
  struct video_data {
      AVClass *class;
      int fd;
      int pixelformat; /* V4L2_PIX_FMT_* */
      int width, height;
      int frame_size;
      int interlaced;
      int top_field_first;
      int ts_mode;
      TimeFilter *timefilter;
      int64_t last_time_m;
  
      int buffers;
      volatile int buffers_queued;
      void **buf_start;
      unsigned int *buf_len;
      char *standard;
      v4l2_std_id std_id;
      int channel;
      char *pixel_format; /**< Set by a private option. */
      int list_format;    /**< Set by a private option. */
      int list_standard;  /**< Set by a private option. */
      char *framerate;    /**< Set by a private option. */
  
      int use_libv4l2;
      int (*open_f)(const char *file, int oflag, ...);
      int (*close_f)(int fd);
      int (*dup_f)(int fd);
      int (*ioctl_f)(int fd, unsigned long int request, ...);
      ssize_t (*read_f)(int fd, void *buffer, size_t n);
      void *(*mmap_f)(void *start, size_t length, int prot, int flags, int fd, int64_t offset);
      int (*munmap_f)(void *_start, size_t length);
  };
  
  struct buff_data {
      struct video_data *s;
      int index;
  };
  
  static int device_open(AVFormatContext *ctx)
  {
      struct video_data *s = ctx->priv_data;
      struct v4l2_capability cap;
      int fd;
      int err;
      int flags = O_RDWR;
  
  #define SET_WRAPPERS(prefix) do {       \
      s->open_f   = prefix ## open;       \
      s->close_f  = prefix ## close;      \
      s->dup_f    = prefix ## dup;        \
      s->ioctl_f  = prefix ## ioctl;      \
      s->read_f   = prefix ## read;       \
      s->mmap_f   = prefix ## mmap;       \
      s->munmap_f = prefix ## munmap;     \
  } while (0)
  
      if (s->use_libv4l2) {
  #if CONFIG_LIBV4L2
          SET_WRAPPERS(v4l2_);
  #else
          av_log(ctx, AV_LOG_ERROR, "libavdevice is not build with libv4l2 support.\n");
          return AVERROR(EINVAL);
  #endif
      } else {
          SET_WRAPPERS();
      }
  
  #define v4l2_open   s->open_f
  #define v4l2_close  s->close_f
  #define v4l2_dup    s->dup_f
  #define v4l2_ioctl  s->ioctl_f
  #define v4l2_read   s->read_f
  #define v4l2_mmap   s->mmap_f
  #define v4l2_munmap s->munmap_f
  
      if (ctx->flags & AVFMT_FLAG_NONBLOCK) {
          flags |= O_NONBLOCK;
      }
  
      fd = v4l2_open(ctx->filename, flags, 0);
      if (fd < 0) {
          err = AVERROR(errno);
          av_log(ctx, AV_LOG_ERROR, "Cannot open video device %s: %s\n",
                 ctx->filename, av_err2str(err));
          return err;
      }
  
      if (v4l2_ioctl(fd, VIDIOC_QUERYCAP, &cap) < 0) {
          err = AVERROR(errno);
          av_log(ctx, AV_LOG_ERROR, "ioctl(VIDIOC_QUERYCAP): %s\n",
                 av_err2str(err));
          goto fail;
      }
  
      av_log(ctx, AV_LOG_VERBOSE, "fd:%d capabilities:%x\n",
             fd, cap.capabilities);
  
      if (!(cap.capabilities & V4L2_CAP_VIDEO_CAPTURE)) {
          av_log(ctx, AV_LOG_ERROR, "Not a video capture device.\n");
          err = AVERROR(ENODEV);
          goto fail;
      }
  
      if (!(cap.capabilities & V4L2_CAP_STREAMING)) {
          av_log(ctx, AV_LOG_ERROR,
                 "The device does not support the streaming I/O method.\n");
          err = AVERROR(ENOSYS);
          goto fail;
      }
  
      return fd;
  
  fail:
      v4l2_close(fd);
      return err;
  }
  
  static int device_init(AVFormatContext *ctx, int *width, int *height,
                         uint32_t pixelformat)
  {
      struct video_data *s = ctx->priv_data;
      struct v4l2_format fmt = { .type = V4L2_BUF_TYPE_VIDEO_CAPTURE };
      int res = 0;
  
      fmt.fmt.pix.width = *width;
      fmt.fmt.pix.height = *height;
      fmt.fmt.pix.pixelformat = pixelformat;
      fmt.fmt.pix.field = V4L2_FIELD_ANY;
  
      /* Some drivers will fail and return EINVAL when the pixelformat
         is not supported (even if type field is valid and supported) */
      if (v4l2_ioctl(s->fd, VIDIOC_S_FMT, &fmt) < 0)
          res = AVERROR(errno);
  
      if ((*width != fmt.fmt.pix.width) || (*height != fmt.fmt.pix.height)) {
          av_log(ctx, AV_LOG_INFO,
                 "The V4L2 driver changed the video from %dx%d to %dx%d\n",
                 *width, *height, fmt.fmt.pix.width, fmt.fmt.pix.height);
          *width = fmt.fmt.pix.width;
          *height = fmt.fmt.pix.height;
      }
  
      if (pixelformat != fmt.fmt.pix.pixelformat) {
          av_log(ctx, AV_LOG_DEBUG,
                 "The V4L2 driver changed the pixel format "
                 "from 0x%08X to 0x%08X\n",
                 pixelformat, fmt.fmt.pix.pixelformat);
          res = AVERROR(EINVAL);
      }
  
      if (fmt.fmt.pix.field == V4L2_FIELD_INTERLACED) {
          av_log(ctx, AV_LOG_DEBUG,
                 "The V4L2 driver is using the interlaced mode\n");
          s->interlaced = 1;
      }
  
      return res;
  }
  
  static int first_field(const struct video_data *s)
  {
      int res;
      v4l2_std_id std;
  
      res = v4l2_ioctl(s->fd, VIDIOC_G_STD, &std);
      if (res < 0)
          return 0;
      if (std & V4L2_STD_NTSC)
          return 0;
  
      return 1;
  }
  
  #if HAVE_STRUCT_V4L2_FRMIVALENUM_DISCRETE
  static void list_framesizes(AVFormatContext *ctx, uint32_t pixelformat)
  {
      const struct video_data *s = ctx->priv_data;
      struct v4l2_frmsizeenum vfse = { .pixel_format = pixelformat };
  
      while(!v4l2_ioctl(s->fd, VIDIOC_ENUM_FRAMESIZES, &vfse)) {
          switch (vfse.type) {
          case V4L2_FRMSIZE_TYPE_DISCRETE:
              av_log(ctx, AV_LOG_INFO, " %ux%u",
                     vfse.discrete.width, vfse.discrete.height);
          break;
          case V4L2_FRMSIZE_TYPE_CONTINUOUS:
          case V4L2_FRMSIZE_TYPE_STEPWISE:
              av_log(ctx, AV_LOG_INFO, " {%u-%u, %u}x{%u-%u, %u}",
                     vfse.stepwise.min_width,
                     vfse.stepwise.max_width,
                     vfse.stepwise.step_width,
                     vfse.stepwise.min_height,
                     vfse.stepwise.max_height,
                     vfse.stepwise.step_height);
          }
          vfse.index++;
      }
  }
  #endif
  
  static void list_formats(AVFormatContext *ctx, int type)
  {
      const struct video_data *s = ctx->priv_data;
      struct v4l2_fmtdesc vfd = { .type = V4L2_BUF_TYPE_VIDEO_CAPTURE };
  
      while(!v4l2_ioctl(s->fd, VIDIOC_ENUM_FMT, &vfd)) {
          enum AVCodecID codec_id = ff_fmt_v4l2codec(vfd.pixelformat);
          enum AVPixelFormat pix_fmt = ff_fmt_v4l2ff(vfd.pixelformat, codec_id);
  
          vfd.index++;
  
          if (!(vfd.flags & V4L2_FMT_FLAG_COMPRESSED) &&
              type & V4L_RAWFORMATS) {
              const char *fmt_name = av_get_pix_fmt_name(pix_fmt);
              av_log(ctx, AV_LOG_INFO, "Raw       : %11s : %20s :",
                     fmt_name ? fmt_name : "Unsupported",
                     vfd.description);
          } else if (vfd.flags & V4L2_FMT_FLAG_COMPRESSED &&
                     type & V4L_COMPFORMATS) {
              const AVCodecDescriptor *desc = avcodec_descriptor_get(codec_id);
              av_log(ctx, AV_LOG_INFO, "Compressed: %11s : %20s :",
                     desc ? desc->name : "Unsupported",
                     vfd.description);
          } else {
              continue;
          }
  
  #ifdef V4L2_FMT_FLAG_EMULATED
          if (vfd.flags & V4L2_FMT_FLAG_EMULATED)
              av_log(ctx, AV_LOG_INFO, " Emulated :");
  #endif
  #if HAVE_STRUCT_V4L2_FRMIVALENUM_DISCRETE
          list_framesizes(ctx, vfd.pixelformat);
  #endif
          av_log(ctx, AV_LOG_INFO, "\n");
      }
  }
  
  static void list_standards(AVFormatContext *ctx)
  {
      int ret;
      struct video_data *s = ctx->priv_data;
      struct v4l2_standard standard;
  
      if (s->std_id == 0)
          return;
  
      for (standard.index = 0; ; standard.index++) {
          if (v4l2_ioctl(s->fd, VIDIOC_ENUMSTD, &standard) < 0) {
              ret = AVERROR(errno);
              if (ret == AVERROR(EINVAL)) {
                  break;
              } else {
                  av_log(ctx, AV_LOG_ERROR, "ioctl(VIDIOC_ENUMSTD): %s\n", av_err2str(ret));
                  return;
              }
          }
          av_log(ctx, AV_LOG_INFO, "%2d, %16"PRIx64", %s\n",
                 standard.index, (uint64_t)standard.id, standard.name);
      }
  }
  
  static int mmap_init(AVFormatContext *ctx)
  {
      int i, res;
      struct video_data *s = ctx->priv_data;
      struct v4l2_requestbuffers req = {
          .type   = V4L2_BUF_TYPE_VIDEO_CAPTURE,
          .count  = desired_video_buffers,
          .memory = V4L2_MEMORY_MMAP
      };
  
      if (v4l2_ioctl(s->fd, VIDIOC_REQBUFS, &req) < 0) {
          res = AVERROR(errno);
          av_log(ctx, AV_LOG_ERROR, "ioctl(VIDIOC_REQBUFS): %s\n", av_err2str(res));
          return res;
      }
  
      if (req.count < 2) {
          av_log(ctx, AV_LOG_ERROR, "Insufficient buffer memory\n");
          return AVERROR(ENOMEM);
      }
      s->buffers = req.count;
      s->buf_start = av_malloc_array(s->buffers, sizeof(void *));
      if (!s->buf_start) {
          av_log(ctx, AV_LOG_ERROR, "Cannot allocate buffer pointers\n");
          return AVERROR(ENOMEM);
      }
      s->buf_len = av_malloc_array(s->buffers, sizeof(unsigned int));
      if (!s->buf_len) {
          av_log(ctx, AV_LOG_ERROR, "Cannot allocate buffer sizes\n");
          av_freep(&s->buf_start);
          return AVERROR(ENOMEM);
      }
  
      for (i = 0; i < req.count; i++) {
          struct v4l2_buffer buf = {
              .type   = V4L2_BUF_TYPE_VIDEO_CAPTURE,
              .index  = i,
              .memory = V4L2_MEMORY_MMAP
          };
          if (v4l2_ioctl(s->fd, VIDIOC_QUERYBUF, &buf) < 0) {
              res = AVERROR(errno);
              av_log(ctx, AV_LOG_ERROR, "ioctl(VIDIOC_QUERYBUF): %s\n", av_err2str(res));
              return res;
          }
  
          s->buf_len[i] = buf.length;
          if (s->frame_size > 0 && s->buf_len[i] < s->frame_size) {
              av_log(ctx, AV_LOG_ERROR,
                     "buf_len[%d] = %d < expected frame size %d\n",
                     i, s->buf_len[i], s->frame_size);
              return AVERROR(ENOMEM);
          }
          s->buf_start[i] = v4l2_mmap(NULL, buf.length,
                                 PROT_READ | PROT_WRITE, MAP_SHARED,
                                 s->fd, buf.m.offset);
  
          if (s->buf_start[i] == MAP_FAILED) {
              res = AVERROR(errno);
              av_log(ctx, AV_LOG_ERROR, "mmap: %s\n", av_err2str(res));
              return res;
          }
      }
  
      return 0;
  }
  
  #if FF_API_DESTRUCT_PACKET
  static void dummy_release_buffer(AVPacket *pkt)
  {
      av_assert0(0);
  }
  #endif
  
  static int enqueue_buffer(struct video_data *s, struct v4l2_buffer *buf)
  {
      int res = 0;
  
      if (v4l2_ioctl(s->fd, VIDIOC_QBUF, buf) < 0) {
          res = AVERROR(errno);
          av_log(NULL, AV_LOG_ERROR, "ioctl(VIDIOC_QBUF): %s\n", av_err2str(res));
      } else {
          avpriv_atomic_int_add_and_fetch(&s->buffers_queued, 1);
      }
  
      return res;
  }
  
  static void mmap_release_buffer(void *opaque, uint8_t *data)
  {
      struct v4l2_buffer buf = { 0 };
      struct buff_data *buf_descriptor = opaque;
      struct video_data *s = buf_descriptor->s;
  
      buf.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
      buf.memory = V4L2_MEMORY_MMAP;
      buf.index = buf_descriptor->index;
      av_free(buf_descriptor);
  
      enqueue_buffer(s, &buf);
  }
  
  #if HAVE_CLOCK_GETTIME && defined(CLOCK_MONOTONIC)
  static int64_t av_gettime_monotonic(void)
  {
      return av_gettime_relative();
  }
  #endif
  
  static int init_convert_timestamp(AVFormatContext *ctx, int64_t ts)
  {
      struct video_data *s = ctx->priv_data;
      int64_t now;
  
      now = av_gettime();
      if (s->ts_mode == V4L_TS_ABS &&
          ts <= now + 1 * AV_TIME_BASE && ts >= now - 10 * AV_TIME_BASE) {
          av_log(ctx, AV_LOG_INFO, "Detected absolute timestamps\n");
          s->ts_mode = V4L_TS_CONVERT_READY;
          return 0;
      }
  #if HAVE_CLOCK_GETTIME && defined(CLOCK_MONOTONIC)
      if (ctx->streams[0]->avg_frame_rate.num) {
          now = av_gettime_monotonic();
          if (s->ts_mode == V4L_TS_MONO2ABS ||
              (ts <= now + 1 * AV_TIME_BASE && ts >= now - 10 * AV_TIME_BASE)) {
              AVRational tb = {AV_TIME_BASE, 1};
              int64_t period = av_rescale_q(1, tb, ctx->streams[0]->avg_frame_rate);
              av_log(ctx, AV_LOG_INFO, "Detected monotonic timestamps, converting\n");
              /* microseconds instead of seconds, MHz instead of Hz */
              s->timefilter = ff_timefilter_new(1, period, 1.0E-6);
              if (!s->timefilter)
                  return AVERROR(ENOMEM);
              s->ts_mode = V4L_TS_CONVERT_READY;
              return 0;
          }
      }
  #endif
      av_log(ctx, AV_LOG_ERROR, "Unknown timestamps\n");
      return AVERROR(EIO);
  }
  
  static int convert_timestamp(AVFormatContext *ctx, int64_t *ts)
  {
      struct video_data *s = ctx->priv_data;
  
      if (s->ts_mode) {
          int r = init_convert_timestamp(ctx, *ts);
          if (r < 0)
              return r;
      }
  #if HAVE_CLOCK_GETTIME && defined(CLOCK_MONOTONIC)
      if (s->timefilter) {
          int64_t nowa = av_gettime();
          int64_t nowm = av_gettime_monotonic();
          ff_timefilter_update(s->timefilter, nowa, nowm - s->last_time_m);
          s->last_time_m = nowm;
          *ts = ff_timefilter_eval(s->timefilter, *ts - nowm);
      }
  #endif
      return 0;
  }
  
  static int mmap_read_frame(AVFormatContext *ctx, AVPacket *pkt)
  {
      struct video_data *s = ctx->priv_data;
      struct v4l2_buffer buf = {
          .type   = V4L2_BUF_TYPE_VIDEO_CAPTURE,
          .memory = V4L2_MEMORY_MMAP
      };
      int res;
  
      pkt->size = 0;
  
      /* FIXME: Some special treatment might be needed in case of loss of signal... */
      while ((res = v4l2_ioctl(s->fd, VIDIOC_DQBUF, &buf)) < 0 && (errno == EINTR));
      if (res < 0) {
          if (errno == EAGAIN)
              return AVERROR(EAGAIN);
  
          res = AVERROR(errno);
          av_log(ctx, AV_LOG_ERROR, "ioctl(VIDIOC_DQBUF): %s\n",
                 av_err2str(res));
          return res;
      }
  
      if (buf.index >= s->buffers) {
          av_log(ctx, AV_LOG_ERROR, "Invalid buffer index received.\n");
          return AVERROR(EINVAL);
      }
      avpriv_atomic_int_add_and_fetch(&s->buffers_queued, -1);
      // always keep at least one buffer queued
      av_assert0(avpriv_atomic_int_get(&s->buffers_queued) >= 1);
  
  #ifdef V4L2_BUF_FLAG_ERROR
      if (buf.flags & V4L2_BUF_FLAG_ERROR) {
          av_log(ctx, AV_LOG_WARNING,
                 "Dequeued v4l2 buffer contains corrupted data (%d bytes).\n",
                 buf.bytesused);
          buf.bytesused = 0;
      } else
  #endif
      {
          /* CPIA is a compressed format and we don't know the exact number of bytes
           * used by a frame, so set it here as the driver announces it. */
          if (ctx->video_codec_id == AV_CODEC_ID_CPIA)
              s->frame_size = buf.bytesused;
  
          if (s->frame_size > 0 && buf.bytesused != s->frame_size) {
              av_log(ctx, AV_LOG_ERROR,
                     "Dequeued v4l2 buffer contains %d bytes, but %d were expected. Flags: 0x%08X.\n",
                     buf.bytesused, s->frame_size, buf.flags);
              enqueue_buffer(s, &buf);
              return AVERROR_INVALIDDATA;
          }
      }
  
      /* Image is at s->buff_start[buf.index] */
      if (avpriv_atomic_int_get(&s->buffers_queued) == FFMAX(s->buffers / 8, 1)) {
          /* when we start getting low on queued buffers, fall back on copying data */
          res = av_new_packet(pkt, buf.bytesused);
          if (res < 0) {
              av_log(ctx, AV_LOG_ERROR, "Error allocating a packet.\n");
              enqueue_buffer(s, &buf);
              return res;
          }
          memcpy(pkt->data, s->buf_start[buf.index], buf.bytesused);
  
          res = enqueue_buffer(s, &buf);
          if (res) {
              av_free_packet(pkt);
              return res;
          }
      } else {
          struct buff_data *buf_descriptor;
  
          pkt->data     = s->buf_start[buf.index];
          pkt->size     = buf.bytesused;
  #if FF_API_DESTRUCT_PACKET
  FF_DISABLE_DEPRECATION_WARNINGS
          pkt->destruct = dummy_release_buffer;
  FF_ENABLE_DEPRECATION_WARNINGS
  #endif
  
          buf_descriptor = av_malloc(sizeof(struct buff_data));
          if (!buf_descriptor) {
              /* Something went wrong... Since av_malloc() failed, we cannot even
               * allocate a buffer for memcpying into it
               */
              av_log(ctx, AV_LOG_ERROR, "Failed to allocate a buffer descriptor\n");
              enqueue_buffer(s, &buf);
  
              return AVERROR(ENOMEM);
          }
          buf_descriptor->index = buf.index;
          buf_descriptor->s     = s;
  
          pkt->buf = av_buffer_create(pkt->data, pkt->size, mmap_release_buffer,
                                      buf_descriptor, 0);
          if (!pkt->buf) {
              av_log(ctx, AV_LOG_ERROR, "Failed to create a buffer\n");
              enqueue_buffer(s, &buf);
              av_freep(&buf_descriptor);
              return AVERROR(ENOMEM);
          }
      }
      pkt->pts = buf.timestamp.tv_sec * INT64_C(1000000) + buf.timestamp.tv_usec;
      convert_timestamp(ctx, &pkt->pts);
  
      return pkt->size;
  }
  
  static int mmap_start(AVFormatContext *ctx)
  {
      struct video_data *s = ctx->priv_data;
      enum v4l2_buf_type type;
      int i, res;
  
      for (i = 0; i < s->buffers; i++) {
          struct v4l2_buffer buf = {
              .type   = V4L2_BUF_TYPE_VIDEO_CAPTURE,
              .index  = i,
              .memory = V4L2_MEMORY_MMAP
          };
  
          if (v4l2_ioctl(s->fd, VIDIOC_QBUF, &buf) < 0) {
              res = AVERROR(errno);
              av_log(ctx, AV_LOG_ERROR, "ioctl(VIDIOC_QBUF): %s\n",
                     av_err2str(res));
              return res;
          }
      }
      s->buffers_queued = s->buffers;
  
      type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
      if (v4l2_ioctl(s->fd, VIDIOC_STREAMON, &type) < 0) {
          res = AVERROR(errno);
          av_log(ctx, AV_LOG_ERROR, "ioctl(VIDIOC_STREAMON): %s\n",
                 av_err2str(res));
          return res;
      }
  
      return 0;
  }
  
  static void mmap_close(struct video_data *s)
  {
      enum v4l2_buf_type type;
      int i;
  
      type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
      /* We do not check for the result, because we could
       * not do anything about it anyway...
       */
      v4l2_ioctl(s->fd, VIDIOC_STREAMOFF, &type);
      for (i = 0; i < s->buffers; i++) {
          v4l2_munmap(s->buf_start[i], s->buf_len[i]);
      }
      av_freep(&s->buf_start);
      av_freep(&s->buf_len);
  }
  
  static int v4l2_set_parameters(AVFormatContext *ctx)
  {
      struct video_data *s = ctx->priv_data;
      struct v4l2_standard standard = { 0 };
      struct v4l2_streamparm streamparm = { 0 };
      struct v4l2_fract *tpf;
      AVRational framerate_q = { 0 };
      int i, ret;
  
      if (s->framerate &&
          (ret = av_parse_video_rate(&framerate_q, s->framerate)) < 0) {
          av_log(ctx, AV_LOG_ERROR, "Could not parse framerate '%s'.\n",
                 s->framerate);
          return ret;
      }
  
      if (s->standard) {
          if (s->std_id) {
              ret = 0;
              av_log(ctx, AV_LOG_DEBUG, "Setting standard: %s\n", s->standard);
              /* set tv standard */
              for (i = 0; ; i++) {
                  standard.index = i;
                  if (v4l2_ioctl(s->fd, VIDIOC_ENUMSTD, &standard) < 0) {
                      ret = AVERROR(errno);
                      break;
                  }
                  if (!av_strcasecmp(standard.name, s->standard))
                      break;
              }
              if (ret < 0) {
                  av_log(ctx, AV_LOG_ERROR, "Unknown or unsupported standard '%s'\n", s->standard);
                  return ret;
              }
  
              if (v4l2_ioctl(s->fd, VIDIOC_S_STD, &standard.id) < 0) {
                  ret = AVERROR(errno);
                  av_log(ctx, AV_LOG_ERROR, "ioctl(VIDIOC_S_STD): %s\n", av_err2str(ret));
                  return ret;
              }
          } else {
              av_log(ctx, AV_LOG_WARNING,
                     "This device does not support any standard\n");
          }
      }
  
      /* get standard */
      if (v4l2_ioctl(s->fd, VIDIOC_G_STD, &s->std_id) == 0) {
          tpf = &standard.frameperiod;
          for (i = 0; ; i++) {
              standard.index = i;
              if (v4l2_ioctl(s->fd, VIDIOC_ENUMSTD, &standard) < 0) {
                  ret = AVERROR(errno);
                  if (ret == AVERROR(EINVAL)
  #ifdef ENODATA
                      || ret == AVERROR(ENODATA)
  #endif
                  ) {
                      tpf = &streamparm.parm.capture.timeperframe;
                      break;
                  }
                  av_log(ctx, AV_LOG_ERROR, "ioctl(VIDIOC_ENUMSTD): %s\n", av_err2str(ret));
                  return ret;
              }
              if (standard.id == s->std_id) {
                  av_log(ctx, AV_LOG_DEBUG,
                         "Current standard: %s, id: %"PRIx64", frameperiod: %d/%d\n",
                         standard.name, (uint64_t)standard.id, tpf->numerator, tpf->denominator);
                  break;
              }
          }
      } else {
          tpf = &streamparm.parm.capture.timeperframe;
      }
  
      streamparm.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
      if (v4l2_ioctl(s->fd, VIDIOC_G_PARM, &streamparm) < 0) {
          ret = AVERROR(errno);
          av_log(ctx, AV_LOG_ERROR, "ioctl(VIDIOC_G_PARM): %s\n", av_err2str(ret));
          return ret;
      }
  
      if (framerate_q.num && framerate_q.den) {
          if (streamparm.parm.capture.capability & V4L2_CAP_TIMEPERFRAME) {
              tpf = &streamparm.parm.capture.timeperframe;
  
              av_log(ctx, AV_LOG_DEBUG, "Setting time per frame to %d/%d\n",
                     framerate_q.den, framerate_q.num);
              tpf->numerator   = framerate_q.den;
              tpf->denominator = framerate_q.num;
  
              if (v4l2_ioctl(s->fd, VIDIOC_S_PARM, &streamparm) < 0) {
                  ret = AVERROR(errno);
                  av_log(ctx, AV_LOG_ERROR, "ioctl(VIDIOC_S_PARM): %s\n",
                         av_err2str(ret));
                  return ret;
              }
  
              if (framerate_q.num != tpf->denominator ||
                  framerate_q.den != tpf->numerator) {
                  av_log(ctx, AV_LOG_INFO,
                         "The driver changed the time per frame from "
                         "%d/%d to %d/%d\n",
                         framerate_q.den, framerate_q.num,
                         tpf->numerator, tpf->denominator);
              }
          } else {
              av_log(ctx, AV_LOG_WARNING,
                     "The driver does not permit changing the time per frame\n");
          }
      }
      if (tpf->denominator > 0 && tpf->numerator > 0) {
          ctx->streams[0]->avg_frame_rate.num = tpf->denominator;
          ctx->streams[0]->avg_frame_rate.den = tpf->numerator;
          ctx->streams[0]->r_frame_rate = ctx->streams[0]->avg_frame_rate;
      } else
          av_log(ctx, AV_LOG_WARNING, "Time per frame unknown\n");
  
      return 0;
  }
  
  static int device_try_init(AVFormatContext *ctx,
                             enum AVPixelFormat pix_fmt,
                             int *width,
                             int *height,
                             uint32_t *desired_format,
                             enum AVCodecID *codec_id)
  {
      int ret, i;
  
      *desired_format = ff_fmt_ff2v4l(pix_fmt, ctx->video_codec_id);
  
      if (*desired_format) {
          ret = device_init(ctx, width, height, *desired_format);
          if (ret < 0) {
              *desired_format = 0;
              if (ret != AVERROR(EINVAL))
                  return ret;
          }
      }
  
      if (!*desired_format) {
          for (i = 0; ff_fmt_conversion_table[i].codec_id != AV_CODEC_ID_NONE; i++) {
              if (ctx->video_codec_id == AV_CODEC_ID_NONE ||
                  ff_fmt_conversion_table[i].codec_id == ctx->video_codec_id) {
                  av_log(ctx, AV_LOG_DEBUG, "Trying to set codec:%s pix_fmt:%s\n",
                         avcodec_get_name(ff_fmt_conversion_table[i].codec_id),
                         (char *)av_x_if_null(av_get_pix_fmt_name(ff_fmt_conversion_table[i].ff_fmt), "none"));
  
                  *desired_format = ff_fmt_conversion_table[i].v4l2_fmt;
                  ret = device_init(ctx, width, height, *desired_format);
                  if (ret >= 0)
                      break;
                  else if (ret != AVERROR(EINVAL))
                      return ret;
                  *desired_format = 0;
              }
          }
  
          if (*desired_format == 0) {
              av_log(ctx, AV_LOG_ERROR, "Cannot find a proper format for "
                     "codec '%s' (id %d), pixel format '%s' (id %d)\n",
                     avcodec_get_name(ctx->video_codec_id), ctx->video_codec_id,
                     (char *)av_x_if_null(av_get_pix_fmt_name(pix_fmt), "none"), pix_fmt);
              ret = AVERROR(EINVAL);
          }
      }
  
      *codec_id = ff_fmt_v4l2codec(*desired_format);
      av_assert0(*codec_id != AV_CODEC_ID_NONE);
      return ret;
  }
  
  static int v4l2_read_probe(AVProbeData *p)
  {
      if (av_strstart(p->filename, "/dev/video", NULL))
          return AVPROBE_SCORE_MAX - 1;
      return 0;
  }
  
  static int v4l2_read_header(AVFormatContext *ctx)
  {
      struct video_data *s = ctx->priv_data;
      AVStream *st;
      int res = 0;
      uint32_t desired_format;
      enum AVCodecID codec_id = AV_CODEC_ID_NONE;
      enum AVPixelFormat pix_fmt = AV_PIX_FMT_NONE;
      struct v4l2_input input = { 0 };
  
      st = avformat_new_stream(ctx, NULL);
      if (!st)
          return AVERROR(ENOMEM);
  
  #if CONFIG_LIBV4L2
      /* silence libv4l2 logging. if fopen() fails v4l2_log_file will be NULL
         and errors will get sent to stderr */
      if (s->use_libv4l2)
          v4l2_log_file = fopen("/dev/null", "w");
  #endif
  
      s->fd = device_open(ctx);
      if (s->fd < 0)
          return s->fd;
  
      if (s->channel != -1) {
          /* set video input */
          av_log(ctx, AV_LOG_DEBUG, "Selecting input_channel: %d\n", s->channel);
          if (v4l2_ioctl(s->fd, VIDIOC_S_INPUT, &s->channel) < 0) {
              res = AVERROR(errno);
              av_log(ctx, AV_LOG_ERROR, "ioctl(VIDIOC_S_INPUT): %s\n", av_err2str(res));
              goto fail;
          }
      } else {
          /* get current video input */
          if (v4l2_ioctl(s->fd, VIDIOC_G_INPUT, &s->channel) < 0) {
              res = AVERROR(errno);
              av_log(ctx, AV_LOG_ERROR, "ioctl(VIDIOC_G_INPUT): %s\n", av_err2str(res));
              goto fail;
          }
      }
  
      /* enum input */
      input.index = s->channel;
      if (v4l2_ioctl(s->fd, VIDIOC_ENUMINPUT, &input) < 0) {
          res = AVERROR(errno);
          av_log(ctx, AV_LOG_ERROR, "ioctl(VIDIOC_ENUMINPUT): %s\n", av_err2str(res));
          goto fail;
      }
      s->std_id = input.std;
      av_log(ctx, AV_LOG_DEBUG, "Current input_channel: %d, input_name: %s, input_std: %"PRIx64"\n",
             s->channel, input.name, (uint64_t)input.std);
  
      if (s->list_format) {
          list_formats(ctx, s->list_format);
          res = AVERROR_EXIT;
          goto fail;
      }
  
      if (s->list_standard) {
          list_standards(ctx);
          res = AVERROR_EXIT;
          goto fail;
      }
  
      avpriv_set_pts_info(st, 64, 1, 1000000); /* 64 bits pts in us */
  
      if (s->pixel_format) {
          AVCodec *codec = avcodec_find_decoder_by_name(s->pixel_format);
  
          if (codec)
              ctx->video_codec_id = codec->id;
  
          pix_fmt = av_get_pix_fmt(s->pixel_format);
  
          if (pix_fmt == AV_PIX_FMT_NONE && !codec) {
              av_log(ctx, AV_LOG_ERROR, "No such input format: %s.\n",
                     s->pixel_format);
  
              res = AVERROR(EINVAL);
              goto fail;
          }
      }
  
      if (!s->width && !s->height) {
          struct v4l2_format fmt = { .type = V4L2_BUF_TYPE_VIDEO_CAPTURE };
  
          av_log(ctx, AV_LOG_VERBOSE,
                 "Querying the device for the current frame size\n");
          if (v4l2_ioctl(s->fd, VIDIOC_G_FMT, &fmt) < 0) {
              res = AVERROR(errno);
              av_log(ctx, AV_LOG_ERROR, "ioctl(VIDIOC_G_FMT): %s\n",
                     av_err2str(res));
              goto fail;
          }
  
          s->width  = fmt.fmt.pix.width;
          s->height = fmt.fmt.pix.height;
          av_log(ctx, AV_LOG_VERBOSE,
                 "Setting frame size to %dx%d\n", s->width, s->height);
      }
  
      res = device_try_init(ctx, pix_fmt, &s->width, &s->height, &desired_format, &codec_id);
      if (res < 0)
          goto fail;
  
      /* If no pixel_format was specified, the codec_id was not known up
       * until now. Set video_codec_id in the context, as codec_id will
       * not be available outside this function
       */
      if (codec_id != AV_CODEC_ID_NONE && ctx->video_codec_id == AV_CODEC_ID_NONE)
          ctx->video_codec_id = codec_id;
  
      if ((res = av_image_check_size(s->width, s->height, 0, ctx)) < 0)
          goto fail;
  
      s->pixelformat = desired_format;
  
      if ((res = v4l2_set_parameters(ctx)) < 0)
          goto fail;
  
      st->codec->pix_fmt = ff_fmt_v4l2ff(desired_format, codec_id);
      s->frame_size =
          avpicture_get_size(st->codec->pix_fmt, s->width, s->height);
  
      if ((res = mmap_init(ctx)) ||
          (res = mmap_start(ctx)) < 0)
              goto fail;
  
      s->top_field_first = first_field(s);
  
      st->codec->codec_type = AVMEDIA_TYPE_VIDEO;
      st->codec->codec_id = codec_id;
      if (codec_id == AV_CODEC_ID_RAWVIDEO)
          st->codec->codec_tag =
              avcodec_pix_fmt_to_codec_tag(st->codec->pix_fmt);
      else if (codec_id == AV_CODEC_ID_H264) {
          st->need_parsing = AVSTREAM_PARSE_FULL_ONCE;
      }
      if (desired_format == V4L2_PIX_FMT_YVU420)
          st->codec->codec_tag = MKTAG('Y', 'V', '1', '2');
      else if (desired_format == V4L2_PIX_FMT_YVU410)
          st->codec->codec_tag = MKTAG('Y', 'V', 'U', '9');
      st->codec->width = s->width;
      st->codec->height = s->height;
      if (st->avg_frame_rate.den)
          st->codec->bit_rate = s->frame_size * av_q2d(st->avg_frame_rate) * 8;
  
      return 0;
  
  fail:
      v4l2_close(s->fd);
      return res;
  }
  
  static int v4l2_read_packet(AVFormatContext *ctx, AVPacket *pkt)
  {
      struct video_data *s = ctx->priv_data;
  #if FF_API_CODED_FRAME
  FF_DISABLE_DEPRECATION_WARNINGS
      AVFrame *frame = ctx->streams[0]->codec->coded_frame;
  FF_ENABLE_DEPRECATION_WARNINGS
  #endif
      int res;
  
      av_init_packet(pkt);
      if ((res = mmap_read_frame(ctx, pkt)) < 0) {
          return res;
      }
  
  #if FF_API_CODED_FRAME
  FF_DISABLE_DEPRECATION_WARNINGS
      if (frame && s->interlaced) {
          frame->interlaced_frame = 1;
          frame->top_field_first = s->top_field_first;
      }
  FF_ENABLE_DEPRECATION_WARNINGS
  #endif
  
      return pkt->size;
  }
  
  static int v4l2_read_close(AVFormatContext *ctx)
  {
      struct video_data *s = ctx->priv_data;
  
      if (avpriv_atomic_int_get(&s->buffers_queued) != s->buffers)
          av_log(ctx, AV_LOG_WARNING, "Some buffers are still owned by the caller on "
                 "close.\n");
  
      mmap_close(s);
  
      v4l2_close(s->fd);
      return 0;
  }
  
  static int v4l2_is_v4l_dev(const char *name)
  {
      return !strncmp(name, "video", 5) ||
             !strncmp(name, "radio", 5) ||
             !strncmp(name, "vbi", 3) ||
             !strncmp(name, "v4l-subdev", 10);
  }
  
  static int v4l2_get_device_list(AVFormatContext *ctx, AVDeviceInfoList *device_list)
  {
      struct video_data *s = ctx->priv_data;
      DIR *dir;
      struct dirent *entry;
      AVDeviceInfo *device = NULL;
      struct v4l2_capability cap;
      int ret = 0;
  
      if (!device_list)
          return AVERROR(EINVAL);
  
      dir = opendir("/dev");
      if (!dir) {
          ret = AVERROR(errno);
          av_log(ctx, AV_LOG_ERROR, "Couldn't open the directory: %s\n", av_err2str(ret));
          return ret;
      }
      while ((entry = readdir(dir))) {
          if (!v4l2_is_v4l_dev(entry->d_name))
              continue;
  
          snprintf(ctx->filename, sizeof(ctx->filename), "/dev/%s", entry->d_name);
          if ((s->fd = device_open(ctx)) < 0)
              continue;
  
          if (v4l2_ioctl(s->fd, VIDIOC_QUERYCAP, &cap) < 0) {
              ret = AVERROR(errno);
              av_log(ctx, AV_LOG_ERROR, "ioctl(VIDIOC_QUERYCAP): %s\n", av_err2str(ret));
              goto fail;
          }
  
          device = av_mallocz(sizeof(AVDeviceInfo));
          if (!device) {
              ret = AVERROR(ENOMEM);
              goto fail;
          }
          device->device_name = av_strdup(ctx->filename);
          device->device_description = av_strdup(cap.card);
          if (!device->device_name || !device->device_description) {
              ret = AVERROR(ENOMEM);
              goto fail;
          }
  
          if ((ret = av_dynarray_add_nofree(&device_list->devices,
                                            &device_list->nb_devices, device)) < 0)
              goto fail;
  
          v4l2_close(s->fd);
          s->fd = -1;
          continue;
  
        fail:
          if (device) {
              av_freep(&device->device_name);
              av_freep(&device->device_description);
              av_freep(&device);
          }
          if (s->fd >= 0)
              v4l2_close(s->fd);
          s->fd = -1;
          break;
      }
      closedir(dir);
      return ret;
  }
  
  #define OFFSET(x) offsetof(struct video_data, x)
  #define DEC AV_OPT_FLAG_DECODING_PARAM
  
  static const AVOption options[] = {
      { "standard",     "set TV standard, used only by analog frame grabber",       OFFSET(standard),     AV_OPT_TYPE_STRING, {.str = NULL }, 0, 0,       DEC },
      { "channel",      "set TV channel, used only by frame grabber",               OFFSET(channel),      AV_OPT_TYPE_INT,    {.i64 = -1 },  -1, INT_MAX, DEC },
      { "video_size",   "set frame size",                                           OFFSET(width),        AV_OPT_TYPE_IMAGE_SIZE, {.str = NULL},  0, 0,   DEC },
      { "pixel_format", "set preferred pixel format",                               OFFSET(pixel_format), AV_OPT_TYPE_STRING, {.str = NULL},  0, 0,       DEC },
      { "input_format", "set preferred pixel format (for raw video) or codec name", OFFSET(pixel_format), AV_OPT_TYPE_STRING, {.str = NULL},  0, 0,       DEC },
      { "framerate",    "set frame rate",                                           OFFSET(framerate),    AV_OPT_TYPE_STRING, {.str = NULL},  0, 0,       DEC },
  
      { "list_formats", "list available formats and exit",                          OFFSET(list_format),  AV_OPT_TYPE_INT,    {.i64 = 0 },  0, INT_MAX, DEC, "list_formats" },
      { "all",          "show all available formats",                               OFFSET(list_format),  AV_OPT_TYPE_CONST,  {.i64 = V4L_ALLFORMATS  },    0, INT_MAX, DEC, "list_formats" },
      { "raw",          "show only non-compressed formats",                         OFFSET(list_format),  AV_OPT_TYPE_CONST,  {.i64 = V4L_RAWFORMATS  },    0, INT_MAX, DEC, "list_formats" },
      { "compressed",   "show only compressed formats",                             OFFSET(list_format),  AV_OPT_TYPE_CONST,  {.i64 = V4L_COMPFORMATS },    0, INT_MAX, DEC, "list_formats" },
  
      { "list_standards", "list supported standards and exit",                      OFFSET(list_standard), AV_OPT_TYPE_INT,   {.i64 = 0 },  0, 1, DEC, "list_standards" },
      { "all",            "show all supported standards",                           OFFSET(list_standard), AV_OPT_TYPE_CONST, {.i64 = 1 },  0, 0, DEC, "list_standards" },
  
      { "timestamps",   "set type of timestamps for grabbed frames",                OFFSET(ts_mode),      AV_OPT_TYPE_INT,    {.i64 = 0 }, 0, 2, DEC, "timestamps" },
      { "ts",           "set type of timestamps for grabbed frames",                OFFSET(ts_mode),      AV_OPT_TYPE_INT,    {.i64 = 0 }, 0, 2, DEC, "timestamps" },
      { "default",      "use timestamps from the kernel",                           OFFSET(ts_mode),      AV_OPT_TYPE_CONST,  {.i64 = V4L_TS_DEFAULT  }, 0, 2, DEC, "timestamps" },
      { "abs",          "use absolute timestamps (wall clock)",                     OFFSET(ts_mode),      AV_OPT_TYPE_CONST,  {.i64 = V4L_TS_ABS      }, 0, 2, DEC, "timestamps" },
      { "mono2abs",     "force conversion from monotonic to absolute timestamps",   OFFSET(ts_mode),      AV_OPT_TYPE_CONST,  {.i64 = V4L_TS_MONO2ABS }, 0, 2, DEC, "timestamps" },
      { "use_libv4l2",  "use libv4l2 (v4l-utils) conversion functions",             OFFSET(use_libv4l2),  AV_OPT_TYPE_INT,    {.i64 = 0}, 0, 1, DEC },
      { NULL },
  };
  
  static const AVClass v4l2_class = {
      .class_name = "V4L2 indev",
      .item_name  = av_default_item_name,
      .option     = options,
      .version    = LIBAVUTIL_VERSION_INT,
      .category   = AV_CLASS_CATEGORY_DEVICE_VIDEO_INPUT,
  };
  
  AVInputFormat ff_v4l2_demuxer = {
      .name           = "video4linux2,v4l2",
      .long_name      = NULL_IF_CONFIG_SMALL("Video4Linux2 device grab"),
      .priv_data_size = sizeof(struct video_data),
      .read_probe     = v4l2_read_probe,
      .read_header    = v4l2_read_header,
      .read_packet    = v4l2_read_packet,
      .read_close     = v4l2_read_close,
      .get_device_list = v4l2_get_device_list,
      .flags          = AVFMT_NOFILE,
      .priv_class     = &v4l2_class,
  };
  