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_FILTERS_FFMPEG_AUDIO_DECODER_H_
  #define MEDIA_FILTERS_FFMPEG_AUDIO_DECODER_H_
  
  #include <list>
  #include <memory>
  
  #include "base/callback.h"
  #include "base/macros.h"
  #include "base/time/time.h"
  #include "media/base/audio_buffer.h"
  #include "media/base/audio_decoder.h"
  #include "media/base/demuxer_stream.h"
  #include "media/base/media_log.h"
  #include "media/base/sample_format.h"
  #include "media/ffmpeg/ffmpeg_deleters.h"
  
  struct AVCodecContext;
  struct AVFrame;
  
  namespace base {
  class SingleThreadTaskRunner;
  }
  
  namespace media {
  
  class AudioDiscardHelper;
  class DecoderBuffer;
  class FFmpegDecodingLoop;
  
  class MEDIA_EXPORT FFmpegAudioDecoder : public AudioDecoder {
   public:
    FFmpegAudioDecoder(
        const scoped_refptr<base::SingleThreadTaskRunner>& task_runner,
        MediaLog* media_log);
    ~FFmpegAudioDecoder() override;
  
    // AudioDecoder implementation.
    std::string GetDisplayName() const override;
    void Initialize(
        const AudioDecoderConfig& config,
        CdmContext* cdm_context,
        const InitCB& init_cb,
        const OutputCB& output_cb,
        const WaitingForDecryptionKeyCB& waiting_for_decryption_key_cb) override;
    void Decode(scoped_refptr<DecoderBuffer> buffer,
                const DecodeCB& decode_cb) override;
    void Reset(const base::Closure& closure) override;
  
    // Callback called from within FFmpeg to allocate a buffer based on the
    // properties of |codec_context| and |frame|. See AVCodecContext.get_buffer2
    // documentation inside FFmpeg.
    int GetAudioBuffer(struct AVCodecContext* s, AVFrame* frame, int flags);
  
   private:
    // There are four states the decoder can be in:
    //
    // - kUninitialized: The decoder is not initialized.
    // - kNormal: This is the normal state. The decoder is idle and ready to
    //            decode input buffers, or is decoding an input buffer.
    // - kDecodeFinished: EOS buffer received, codec flushed and decode finished.
    //                    No further Decode() call should be made.
    // - kError: Unexpected error happened.
    //
    // These are the possible state transitions.
    //
    // kUninitialized -> kNormal:
    //     The decoder is successfully initialized and is ready to decode buffers.
    // kNormal -> kDecodeFinished:
    //     When buffer->end_of_stream() is true.
    // kNormal -> kError:
    //     A decoding error occurs and decoding needs to stop.
    // (any state) -> kNormal:
    //     Any time Reset() is called.
    enum DecoderState {
      kUninitialized,
      kNormal,
      kDecodeFinished,
      kError
    };
  
    // Reset decoder and call |reset_cb_|.
    void DoReset();
  
    // Handles decoding an unencrypted encoded buffer.
    void DecodeBuffer(const DecoderBuffer& buffer, const DecodeCB& decode_cb);
    bool FFmpegDecode(const DecoderBuffer& buffer);
    bool OnNewFrame(const DecoderBuffer& buffer,
                    bool* decoded_frame_this_loop,
                    AVFrame* frame);
  
    // Handles (re-)initializing the decoder with a (new) config.
    // Returns true if initialization was successful.
    bool ConfigureDecoder(const AudioDecoderConfig& config);
  
    // Releases resources associated with |codec_context_| .
    void ReleaseFFmpegResources();
  
    void ResetTimestampState(const AudioDecoderConfig& config);
  
    scoped_refptr<base::SingleThreadTaskRunner> task_runner_;
  
    OutputCB output_cb_;
  
    DecoderState state_;
  
    // FFmpeg structures owned by this object.
    std::unique_ptr<AVCodecContext, ScopedPtrAVFreeContext> codec_context_;
  
    AudioDecoderConfig config_;
  
    // AVSampleFormat initially requested; not Chrome's SampleFormat.
    int av_sample_format_;
  
    std::unique_ptr<AudioDiscardHelper> discard_helper_;
  
    MediaLog* media_log_;
  
    scoped_refptr<AudioBufferMemoryPool> pool_;
  
    std::unique_ptr<FFmpegDecodingLoop> decoding_loop_;
  
    DISALLOW_IMPLICIT_CONSTRUCTORS(FFmpegAudioDecoder);
  };
  
  }  // namespace media
  
  #endif  // MEDIA_FILTERS_FFMPEG_AUDIO_DECODER_H_
  