Introduce AudioDiscardHelper. Refactor audio decoders to use it.

media/filters/ffmpeg_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_FILTERS_FFMPEG_AUDIO_DECODER_H_
 #define MEDIA_FILTERS_FFMPEG_AUDIO_DECODER_H_
 
 #include <list>
 
 #include "base/callback.h"
 #include "base/memory/scoped_ptr.h"
 #include "base/time/time.h"
 #include "media/base/audio_decoder.h"
 #include "media/base/demuxer_stream.h"
 #include "media/base/sample_format.h"
 #include "media/ffmpeg/ffmpeg_deleters.h"
 
 struct AVCodecContext;
 struct AVFrame;
 
 namespace base {
 class SingleThreadTaskRunner;
 }
 
 namespace media {
 
-class AudioTimestampHelper;
+class AudioDiscardHelper;
 class DecoderBuffer;
 
 class MEDIA_EXPORT FFmpegAudioDecoder : public AudioDecoder {
  public:
   explicit FFmpegAudioDecoder(
       const scoped_refptr<base::SingleThreadTaskRunner>& task_runner);
   virtual ~FFmpegAudioDecoder();
 
   // AudioDecoder implementation.
   virtual void Initialize(const AudioDecoderConfig& config,
@@ skipping 36 matching lines @@
 
   // FFmpeg structures owned by this object.
   scoped_ptr<AVCodecContext, ScopedPtrAVFreeContext> codec_context_;
   scoped_ptr<AVFrame, ScopedPtrAVFreeFrame> av_frame_;
 
   AudioDecoderConfig config_;
 
   // AVSampleFormat initially requested; not Chrome's SampleFormat.
   int av_sample_format_;
 
-  // Used for computing output timestamps.
-  scoped_ptr<AudioTimestampHelper> output_timestamp_helper_;
-  base::TimeDelta last_input_timestamp_;
-
-  // Number of frames to drop before generating output buffers.
-  int output_frames_to_drop_;
+  scoped_ptr<AudioDiscardHelper> discard_helper_;
 
   // Since multiple frames may be decoded from the same packet we need to queue
   // them up.
   std::list<scoped_refptr<AudioBuffer> > queued_audio_;
 
   DISALLOW_IMPLICIT_CONSTRUCTORS(FFmpegAudioDecoder);
 };
 
 }  // namespace media
 
 #endif  // MEDIA_FILTERS_FFMPEG_AUDIO_DECODER_H_