text: // Copyright (c) 2012 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.
  
  #ifndef MEDIA_BASE_VIDEO_DECODER_H_
  #define MEDIA_BASE_VIDEO_DECODER_H_
  
  #include "base/callback.h"
  #include "base/memory/ref_counted.h"
  #include "media/base/media_export.h"
  #include "media/base/pipeline_status.h"
  #include "ui/gfx/size.h"
  
  namespace media {
  
  class DecoderBuffer;
  class VideoDecoderConfig;
  class VideoFrame;
  
  class MEDIA_EXPORT VideoDecoder {
   public:
    // Status codes for decode operations on VideoDecoder.
    enum Status {
      kOk,  // Everything went as planned.
      kAborted,  // Decode was aborted as a result of Reset() being called.
      kNotEnoughData,  // Not enough data to produce a video frame.
      kDecodeError,  // Decoding error happened.
      kDecryptError  // Decrypting error happened.
    };
  
    VideoDecoder();
    virtual ~VideoDecoder();
  
    // Initializes a VideoDecoder with the given |config|, executing the
    // |status_cb| upon completion.
    //
    // Note:
    // 1) The VideoDecoder will be reinitialized if it was initialized before.
    //    Upon reinitialization, all internal buffered frames will be dropped.
    // 2) This method should not be called during pending decode, reset or stop.
    // 3) No VideoDecoder calls except for Stop() should be made before
    //    |status_cb| is executed.
    virtual void Initialize(const VideoDecoderConfig& config,
                            const PipelineStatusCB& status_cb) = 0;
  
    // Requests a |buffer| to be decoded. The status of the decoder and decoded
    // frame are returned via the provided callback. Only one decode may be in
    // flight at any given time.
    //
    // Implementations guarantee that the callback will not be called from within
    // this method.
    //
    // If the returned status is kOk:
    // - Non-EOS (end of stream) frame contains decoded video data.
    // - EOS frame indicates the end of the stream.
    // Otherwise the returned frame must be NULL.
    typedef base::Callback<void(Status,
                                const scoped_refptr<VideoFrame>&)> DecodeCB;
    virtual void Decode(const scoped_refptr<DecoderBuffer>& buffer,
                        const DecodeCB& decode_cb) = 0;
  
    // Resets decoder state, fulfilling all pending DecodeCB and dropping extra
    // queued decoded data. After this call, the decoder is back to an initialized
    // clean state.
    // Note: No VideoDecoder calls should be made before |closure| is executed.
    virtual void Reset(const base::Closure& closure) = 0;
  
    // Stops decoder, fires any pending callbacks and sets the decoder to an
    // uninitialized state. A VideoDecoder cannot be re-initialized after it has
    // been stopped.
    // Note that if Initialize() has been called, Stop() must be called and
    // complete before deleting the decoder.
    virtual void Stop(const base::Closure& closure) = 0;
  
    // Returns true if the output format has an alpha channel. Most formats do not
    // have alpha so the default is false. Override and return true for decoders
    // that return formats with an alpha channel.
    virtual bool HasAlpha() const;
  
    // Returns true if the decoder needs bitstream conversion before decoding.
    virtual bool NeedsBitstreamConversion() const;
  
    // Returns true if the decoder currently has the ability to decode and return
    // a VideoFrame. Most implementations can allocate a new VideoFrame and hence
    // this will always return true. Override and return false for decoders that
    // use a fixed set of VideoFrames for decoding.
    virtual bool CanReadWithoutStalling() const;
  
   private:
    DISALLOW_COPY_AND_ASSIGN(VideoDecoder);
  };
  
  }  // namespace media
  
  #endif  // MEDIA_BASE_VIDEO_DECODER_H_
  