media/base/audio_decoder.h

// 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_AUDIO_DECODER_H_
#define MEDIA_BASE_AUDIO_DECODER_H_

#include <string>

#include "base/callback.h"
#include "base/memory/ref_counted.h"
#include "media/base/audio_decoder_config.h"
#include "media/base/cdm_context.h"
#include "media/base/channel_layout.h"
#include "media/base/decoder_buffer.h"
#include "media/base/media_export.h"
#include "media/base/pipeline_status.h"

namespace media {

class AudioBuffer;
class DemuxerStream;

class MEDIA_EXPORT AudioDecoder {
 public:
  // Status codes for decode operations.
  // TODO(rileya): Now that both AudioDecoder and VideoDecoder Status enums
  // match, break them into a decoder_status.h.
  enum Status {
    kOk,          // We're all good.
    kAborted,     // We aborted as a result of Reset() or destruction.
    kDecodeError  // A decoding error occurred.
  };

  // Callback for VideoDecoder initialization.
  typedef base::Callback<void(bool success)> InitCB;

  // Callback for AudioDecoder to return a decoded frame whenever it becomes
  // available. Only non-EOS frames should be returned via this callback.
  typedef base::Callback<void(const scoped_refptr<AudioBuffer>&)> OutputCB;

  // Callback for Decode(). Called after the decoder has completed decoding
  // corresponding DecoderBuffer, indicating that it's ready to accept another
  // buffer to decode.
  typedef base::Callback<void(Status)> DecodeCB;

  AudioDecoder();

  // Fires any pending callbacks, stops and destroys the decoder.
  // Note: Since this is a destructor, |this| will be destroyed after this call.
  // Make sure the callbacks fired from this call doesn't post any task that
  // depends on |this|.
  virtual ~AudioDecoder();

  // Returns the name of the decoder for logging purpose.
  virtual std::string GetDisplayName() const = 0;

  // Initializes an AudioDecoder with the given DemuxerStream, executing the
  // callback upon completion.
  //
  // |set_cdm_ready_cb| can be used to set/cancel a CdmReadyCB with which the
  // decoder can be notified when a CDM is ready. The decoder can use the CDM to
  // handle encrypted video stream.
  //
  //  |init_cb| is used to return initialization status.
  //  |output_cb| is called for decoded audio buffers (see Decode()).
  virtual void Initialize(const AudioDecoderConfig& config,
                          const SetCdmReadyCB& set_cdm_ready_cb,
                          const InitCB& init_cb,
                          const OutputCB& output_cb) = 0;

  // Requests samples to be decoded. Only one decode may be in flight at any
  // given time. Once the buffer is decoded the decoder calls |decode_cb|.
  // |output_cb| specified in Initialize() is called for each decoded buffer,
  // before or after |decode_cb|.
  //
  // Implementations guarantee that the callbacks will not be called from within
  // this method.
  //
  // If |buffer| is an EOS buffer then the decoder must be flushed, i.e.
  // |output_cb| must be called for each frame pending in the queue and
  // |decode_cb| must be called after that.
  virtual void Decode(const scoped_refptr<DecoderBuffer>& buffer,
                      const DecodeCB& decode_cb) = 0;

  // Resets decoder state. All pending Decode() requests will be finished or
  // aborted before |closure| is called.
  virtual void Reset(const base::Closure& closure) = 0;

 private:
  DISALLOW_COPY_AND_ASSIGN(AudioDecoder);
};

}  // namespace media

#endif  // MEDIA_BASE_AUDIO_DECODER_H_