Adding new function ReadFrames() that returns the audio frame in planar

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 55 matching lines @@
   // Copy frames into |dest|. |frames_to_copy| is the number of frames to copy.
   // |source_frame_offset| specifies how many frames in the buffer to skip
   // first. |dest_frame_offset| is the frame offset in |dest|. The frames are
   // converted from their source format into planar float32 data (which is all
   // that AudioBus handles).
   void ReadFrames(int frames_to_copy,
                   int source_frame_offset,
                   int dest_frame_offset,
                   AudioBus* dest);
 
+  // Copy frames into |std::vector<int32>|. The frames are converted from their
+  // source format into planar int32; note that while each frame use 32 bits
+  // each fame is actually PCM signed 24-bit little-endian.
+  std::vector<int32> ReadFrames();

[DaleCurtis, 2014/09/24 22:30:17]

We don't have a SampleFormat for planar 24 bit, only interleaved 32 bit. Which
do you actually need? Also, I was thinking this would be two methods like:

void ReadFramesInterleaved(int frames_to_copy, SampleFormat output_format, void*
dest);
void ReadFramesPlanar(int frames_to_copy, int plane_length, SampleFormat
output_format, void* dest);

Note, you'll need to be careful about adjusted_frame_count_ and trim_start_.
Implementing a generic method may be overkill if you only expect to output
24-bit PCM, so I'd be fine with something like:

void ReadFramesPlanarS24(int frames_to_copy, int plane_length, int32* dest);

If you always know your input sample format I'd be fine with CHECK_EQ()'ing that
and titling the method appropriately.

+
   // 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);
 
@@ skipping 58 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_