Collapse AudioRendererMixer and OnMoreDataResampler into AudioTransform.

media/base/multi_channel_resampler.cc

 // 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.
 
 #include "media/base/multi_channel_resampler.h"
 
 #include "base/bind.h"
 #include "base/bind_helpers.h"
 #include "base/logging.h"
 #include "media/base/audio_bus.h"
 
 namespace media {
 
 MultiChannelResampler::MultiChannelResampler(int channels,
                                              double io_sample_rate_ratio,
                                              const ReadCB& read_cb)
     : last_frame_count_(0),
-      read_cb_(read_cb) {
+      read_cb_(read_cb),
+      output_frames_ready_(0) {
   // 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)));
   }
 }
 
 MultiChannelResampler::~MultiChannelResampler() {}
 
 void MultiChannelResampler::Resample(AudioBus* audio_bus, int frames) {
   DCHECK_EQ(static_cast<size_t>(audio_bus->channels()), resamplers_.size());
 
   // 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.
-  int frames_done = 0;
+  output_frames_ready_ = 0;

[Chris Rogers, 2012/11/14 23:50:49]

As we discussed, I think we need much better comments (perhaps in the .h file)
about output_frames_ready_, exactly what it is and how it's useful

   int chunk_size = resamplers_[0]->ChunkSize();
-  while (frames_done < frames) {
-    int frames_this_time = std::min(frames - frames_done, chunk_size);
+  while (output_frames_ready_ < frames) {
+    int frames_this_time = std::min(frames - output_frames_ready_, chunk_size);
 
     // Resample each channel.
     for (size_t i = 0; i < resamplers_.size(); ++i) {
       DCHECK_EQ(chunk_size, resamplers_[i]->ChunkSize());
 
       // Depending on the sample-rate scale factor, and the internal buffering
       // used in a SincResampler kernel, this call to Resample() will only
       // sometimes call ProvideInput().  However, if it calls ProvideInput() for
       // the first channel, then it will call it for the remaining channels,
       // since they all buffer in the same way and are processing the same
       // number of frames.
       resamplers_[i]->Resample(
-          audio_bus->channel(i) + frames_done, frames_this_time);
+          audio_bus->channel(i) + output_frames_ready_, frames_this_time);
     }
 
-    frames_done += frames_this_time;
+    output_frames_ready_ += frames_this_time;

[Chris Rogers, 2012/11/14 23:50:49]

I don't understand how at the end of this loop that |output_frames_ready_| can
be anything other than |frames|.  Isn't it required that Resampler() process all
and exactly all of the |frames| requested?  Or is it that |output_frames_ready_|
is queried upstream during/in-the-middle of this loop?

[DaleCurtis, 2012/11/15 00:30:59]

Queried upstream only in the middle of this loop. Which is why I think changing
this to be provided via the callback mechanism makes more sense. I'll change
this in the next patch set.

   }
 }
 
 void MultiChannelResampler::ProvideInput(int channel, float* destination,
                                          int frames) {
   // 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_|).
   if (channel == 0) {
     // Allocate staging arrays on the first request and if the frame size or
@@ skipping 28 matching lines @@
   }
 }
 
 void MultiChannelResampler::Flush() {
   last_frame_count_ = 0;
   for (size_t i = 0; i < resamplers_.size(); ++i)
     resamplers_[i]->Flush();
 }
 
 }  // namespace media