Cleanup and reduce memory usage for MultiChannelResampler.

media/base/multi_channel_resampler.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_BASE_MULTI_CHANNEL_RESAMPLER_H_
 #define MEDIA_BASE_MULTI_CHANNEL_RESAMPLER_H_
 
 #include <vector>
 
 #include "base/callback.h"
@@ skipping 34 matching lines @@
   // Update ratio for all SincResamplers.  SetRatio() will cause reconstruction
   // of the kernels used for resampling.  Not thread safe, do not call while
   // Resample() is in progress.
   void SetRatio(double io_sample_rate_ratio);
 
  private:
   // SincResampler::ReadCB implementation.  ProvideInput() will be called for
   // each channel (in channel order) as SincResampler needs more data.
   void ProvideInput(int channel, int frames, float* destination);
 
-  // Sanity check to ensure that ProvideInput() retrieves the same number of
-  // frames for every channel.
-  int last_frame_count_;
-
   // Source of data for resampling.
   ReadCB read_cb_;
 
   // Each channel has its own high quality resampler.
   ScopedVector<SincResampler> resamplers_;
 
   // Buffers for audio data going into SincResampler from ReadCB.
   scoped_ptr<AudioBus> resampler_audio_bus_;
+
+  // To avoid a memcpy() on the first channel we create a wrapped AudioBus where
+  // the first channel points to the |destination| provided to ProvideInput().
   scoped_ptr<AudioBus> wrapped_resampler_audio_bus_;
-  std::vector<float*> resampler_audio_data_;
 
   // The number of output frames that have successfully been processed during
   // the current Resample() call.
   int output_frames_ready_;
 
   DISALLOW_COPY_AND_ASSIGN(MultiChannelResampler);
 };
 
 }  // namespace media
 
 #endif  // MEDIA_BASE_MULTI_CHANNEL_RESAMPLER_H_