media/base/audio_decoder.h

   1 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
   2 // Use of this source code is governed by a BSD-style license that can be
   3 // found in the LICENSE file.
   4
   5 #ifndef MEDIA_BASE_AUDIO_DECODER_H_
   6 #define MEDIA_BASE_AUDIO_DECODER_H_
   7
   8 #include "base/callback.h"
   9 #include "base/memory/ref_counted.h"
  10 #include "media/base/channel_layout.h"
  11 #include "media/base/pipeline_status.h"
  12 #include "media/base/media_export.h"
  13
  14 namespace media {
  15
  16 class AudioBuffer;
  17 class DemuxerStream;
  18
  19 class MEDIA_EXPORT AudioDecoder {
  20  public:
  21   // Status codes for read operations.
  22   enum Status {
  23     kOk,
  24     kAborted,
  25     kDecodeError,
  26   };
  27
  28   AudioDecoder();
  29   virtual ~AudioDecoder();
  30
  31   // Initializes an AudioDecoder with the given DemuxerStream, executing the
  32   // callback upon completion.
  33   // statistics_cb is used to update global pipeline statistics.
  34   virtual void Initialize(DemuxerStream* stream,
  35                           const PipelineStatusCB& status_cb,
  36                           const StatisticsCB& statistics_cb) = 0;
  37
  38   // Requests samples to be decoded and returned via the provided callback.
  39   // Only one read may be in flight at any given time.
  40   //
  41   // Implementations guarantee that the callback will not be called from within
  42   // this method.
  43   //
  44   // Non-NULL sample buffer pointers will contain decoded audio data or may
  45   // indicate the end of the stream. A NULL buffer pointer indicates an aborted
  46   // Read(). This can happen if the DemuxerStream gets flushed and doesn't have
  47   // any more data to return.
  48   typedef base::Callback<void(Status, const scoped_refptr<AudioBuffer>&)>
  49       ReadCB;
  50   virtual void Read(const ReadCB& read_cb) = 0;
  51
  52   // Resets decoder state, dropping any queued encoded data.
  53   virtual void Reset(const base::Closure& closure) = 0;
  54
  55   // Stops decoder, fires any pending callbacks and sets the decoder to an
  56   // uninitialized state. An AudioDecoder cannot be re-initialized after it has
  57   // been stopped.
  58   // Note that if Initialize() has been called, Stop() must be called and
  59   // complete before deleting the decoder.
  60   virtual void Stop(const base::Closure& closure) = 0;
  61
  62   // Returns various information about the decoded audio format.
  63   virtual int bits_per_channel() = 0;
  64   virtual ChannelLayout channel_layout() = 0;
  65   virtual int samples_per_second() = 0;
  66
  67  private:
  68   DISALLOW_COPY_AND_ASSIGN(AudioDecoder);
  69 };
  70
  71 }  // namespace media
  72
  73 #endif  // MEDIA_BASE_AUDIO_DECODER_H_