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      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   // Initialize 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   // Request 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   // Reset decoder state, dropping any queued encoded data.
     53   virtual void Reset(const base::Closure& closure) = 0;
     54 
     55   // Returns various information about the decoded audio format.
     56   virtual int bits_per_channel() = 0;
     57   virtual ChannelLayout channel_layout() = 0;
     58   virtual int samples_per_second() = 0;
     59 
     60  private:
     61   DISALLOW_COPY_AND_ASSIGN(AudioDecoder);
     62 };
     63 
     64 }  // namespace media
     65 
     66 #endif  // MEDIA_BASE_AUDIO_DECODER_H_
     67