Reduce jitter from uneven SincResampler buffer size requests.

remoting/codec/audio_encoder_opus.cc

Index: remoting/codec/audio_encoder_opus.cc
diff --git a/remoting/codec/audio_encoder_opus.cc b/remoting/codec/audio_encoder_opus.cc
index 15160df75f5b0a2764137245ad472f14deb3e8d6..f7d5dce85cadc704f0989e8ce2d0f3850db63c6a 100644
--- a/remoting/codec/audio_encoder_opus.cc
+++ b/remoting/codec/audio_encoder_opus.cc
@@ -80,6 +80,7 @@ void AudioEncoderOpus::InitEncoder() {
     resampler_.reset(new media::MultiChannelResampler(
         channels_,
         static_cast<double>(sampling_rate_) / kOpusSamplingRate,
+        media::SincResampler::kDefaultBlockSize,

[Sergey Ulanov, 2013/04/29 06:23:37]

I think it would be better to mach default frame size we use in opus. Can you
please define kFrameSamples = 960 in this file and use it here instead of
kDefaultBlockSize? (the frame size is defined in audio_decoder_opus.cc, it's
worth adding a reference to that file).

[Sergey Ulanov, 2013/04/29 07:16:54]

Sorry, just realized that kFrameSamples is already defined in this file, just
use it here, please :-) 

[DaleCurtis, 2013/04/29 22:12:31]

kFrameSamples appears to refer to the output sample size, not the input sample
size.  Is this still what you want?  If the packet size provided to Encode() is
constant, it seems you'd want to use that value.

[Sergey Ulanov, 2013/05/01 02:06:25]

Oh, right. Then it should be frame_size_, which is frame size in input samples.

[DaleCurtis, 2013/05/07 23:49:41]

Hmm, I'm not sure about this, so I've just kept the original behavior for now
and added a TODO(sergeyu) :)

         base::Bind(&AudioEncoderOpus::FetchBytesToResample,
                    base::Unretained(this))));
     resampler_bus_ = media::AudioBus::Create(channels_, kFrameSamples);
@@ -88,7 +89,7 @@ void AudioEncoderOpus::InitEncoder() {
   // Drop leftover data because it's for different sampling rate.
   leftover_samples_ = 0;
   leftover_buffer_size_ =
-      frame_size_ + media::SincResampler::kMaximumLookAheadSize;
+      frame_size_ + media::SincResampler::kDefaultBlockSize;
   leftover_buffer_.reset(
       new int16[leftover_buffer_size_ * channels_]);
 }
@@ -159,7 +160,7 @@ scoped_ptr<AudioPacket> AudioEncoderOpus::Encode(
   encoded_packet->set_channels(channels_);
 
   int prefetch_samples =

[Sergey Ulanov, 2013/05/01 02:06:25]

Not sure if prefetching is still required. If not (i.e. if resampler never
requests more than it needs) then please remove it.

-      resampler_.get() ? media::SincResampler::kMaximumLookAheadSize : 0;
+      resampler_.get() ? media::SincResampler::kDefaultBlockSize : 0;
   int samples_wanted = frame_size_ + prefetch_samples;
 
   while (leftover_samples_ + samples_in_packet >= samples_wanted) {