Reduce jitter from uneven SincResampler buffer size requests.

media/base/multi_channel_resampler.cc

Index: media/base/multi_channel_resampler.cc
diff --git a/media/base/multi_channel_resampler.cc b/media/base/multi_channel_resampler.cc
index 9aa00d88efb20d2cebf6dad4b717432f31938adf..a9aa8d68909fc2bcb238aeef715282d56cf0b50f 100644
--- a/media/base/multi_channel_resampler.cc
+++ b/media/base/multi_channel_resampler.cc
@@ -13,6 +13,7 @@ namespace media {
 
 MultiChannelResampler::MultiChannelResampler(int channels,
                                              double io_sample_rate_ratio,
+                                             size_t request_size,
                                              const ReadCB& read_cb)
     : last_frame_count_(0),
       read_cb_(read_cb),
@@ -20,23 +21,30 @@ MultiChannelResampler::MultiChannelResampler(int channels,
   // Allocate each channel's resampler.
   resamplers_.reserve(channels);
   for (int i = 0; i < channels; ++i) {
-    resamplers_.push_back(new SincResampler(io_sample_rate_ratio, base::Bind(
-        &MultiChannelResampler::ProvideInput, base::Unretained(this), i)));
+    resamplers_.push_back(new SincResampler(
+        io_sample_rate_ratio, request_size, base::Bind(
+            &MultiChannelResampler::ProvideInput, base::Unretained(this), i)));
   }
 }
 
 MultiChannelResampler::~MultiChannelResampler() {}
 
-void MultiChannelResampler::Resample(AudioBus* audio_bus, int frames) {
+void MultiChannelResampler::Resample(int frames, AudioBus* audio_bus) {
   DCHECK_EQ(static_cast<size_t>(audio_bus->channels()), resamplers_.size());
 
+  // Optimize the single channel case to avoid the chunking process below.
+  if (audio_bus->channels() == 1) {
+    resamplers_[0]->Resample(frames, audio_bus->channel(0));
+    return;
+  }
+
   // We need to ensure that SincResampler only calls ProvideInput once for each
   // channel.  To ensure this, we chunk the number of requested frames into
   // SincResampler::ChunkSize() sized chunks.  SincResampler guarantees it will
   // only call ProvideInput() once when we resample this way.
   output_frames_ready_ = 0;
-  int chunk_size = resamplers_[0]->ChunkSize();
   while (output_frames_ready_ < frames) {
+    int chunk_size = resamplers_[0]->ChunkSize();
     int frames_this_time = std::min(frames - output_frames_ready_, chunk_size);
 
     // Resample each channel.
@@ -50,15 +58,16 @@ void MultiChannelResampler::Resample(AudioBus* audio_bus, int frames) {
       // since they all buffer in the same way and are processing the same
       // number of frames.
       resamplers_[i]->Resample(
-          audio_bus->channel(i) + output_frames_ready_, frames_this_time);
+          frames_this_time, audio_bus->channel(i) + output_frames_ready_);
     }
 
     output_frames_ready_ += frames_this_time;
   }
 }
 
-void MultiChannelResampler::ProvideInput(int channel, float* destination,
-                                         int frames) {
+void MultiChannelResampler::ProvideInput(int channel,
+                                         int frames,
+                                         float* destination) {
   // Get the data from the multi-channel provider when the first channel asks
   // for it.  For subsequent channels, we can just dish out the channel data
   // from that (stored in |resampler_audio_bus_|).