Reduce jitter from uneven SincResampler buffer size requests.

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"
 #include "base/memory/scoped_ptr.h"
 #include "base/memory/scoped_vector.h"
 #include "media/base/sinc_resampler.h"
 
 namespace media {
 class AudioBus;
 
 // MultiChannelResampler is a multi channel wrapper for SincResampler; allowing
 // high quality sample rate conversion of multiple channels at once.
 class MEDIA_EXPORT MultiChannelResampler {
  public:
   // Callback type for providing more data into the resampler.  Expects AudioBus
   // to be completely filled with data upon return; zero padded if not enough
   // frames are available to satisfy the request.  |frame_delay| is the number
   // of output frames already processed and can be used to estimate delay.
   typedef base::Callback<void(int frame_delay, AudioBus* audio_bus)> ReadCB;
 
   // Constructs a MultiChannelResampler with the specified |read_cb|, which is
   // used to acquire audio data for resampling.  |io_sample_rate_ratio| is the
-  // ratio of input / output sample rates.
-  MultiChannelResampler(int channels, double io_sample_rate_ratio,
+  // ratio of input / output sample rates.  |request_frames| is the size in
+  // frames of the AudioBus to be filled by |read_cb|.
+  MultiChannelResampler(int channels,
+                        double io_sample_rate_ratio,
+                        size_t request_frames,
                         const ReadCB& read_cb);
   virtual ~MultiChannelResampler();
 
   // Resamples |frames| of data from |read_cb_| into AudioBus.
-  void Resample(AudioBus* audio_bus, int frames);
+  void Resample(int frames, AudioBus* audio_bus);
 
   // Flush all buffered data and reset internal indices.  Not thread safe, do
   // not call while Resample() is in progress.
   void Flush();
 
   // 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, float* destination, int frames);
+  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_;
   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_