Support start trimming post-decoding. Use it with FFmpegDemuxer.

media/base/audio_buffer.h

 // Copyright 2013 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_BUFFER_H_
 #define MEDIA_BASE_AUDIO_BUFFER_H_
 
 #include <vector>
 
 #include "base/memory/aligned_memory.h"
@@ skipping 69 matching lines @@
   // Trim an AudioBuffer by removing |frames_to_trim| frames from the start.
   // Timestamp and duration are adjusted to reflect the fewer frames.
   // Note that repeated calls to TrimStart() may result in timestamp() and
   // duration() being off by a few microseconds due to rounding issues.
   void TrimStart(int frames_to_trim);
 
   // Trim an AudioBuffer by removing |frames_to_trim| frames from the end.
   // Duration is adjusted to reflect the fewer frames.
   void TrimEnd(int frames_to_trim);
 
+  // Trim an AudioBuffer by removing |end - start| frames starting at |start|
+  // and ending at |end|; i.e. exclusive.  Even if start is zero, timestamp() is
+  // not adjusted, only duration().
+  void TrimRange(int start, int end);
+
   // Return the number of channels.
   int channel_count() const { return channel_count_; }
 
   // Return the number of frames held.
   int frame_count() const { return adjusted_frame_count_; }
 
   // Return the sample rate.
   int sample_rate() const { return sample_rate_; }
 
   // Return the channel layout.
@@ skipping 51 matching lines @@
 
   // For planar data, points to each channels data.
   std::vector<uint8*> channel_data_;
 
   DISALLOW_IMPLICIT_CONSTRUCTORS(AudioBuffer);
 };
 
 }  // namespace media
 
 #endif  // MEDIA_BASE_AUDIO_BUFFER_H_