Reland 10952007: Pass through small buffer sizes without FIFO on Linux

media/audio/audio_output_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/audio/audio_output_resampler.h"
 
 #include "base/bind.h"
 #include "base/bind_helpers.h"
 #include "base/command_line.h"
 #include "base/compiler_specific.h"
@@ skipping 114 matching lines @@
     }
 
     // Include bits per channel differences.
     io_ratio_ *= static_cast<double>(params_.bits_per_sample()) /
         output_params_.bits_per_sample();
 
     // Include channel count differences.
     io_ratio_ *= static_cast<double>(params_.channels()) /
         output_params_.channels();
 
+    // We allow the clients to set the buffer size for low latency path.
+    if (output_params_.format() == AudioParameters::AUDIO_PCM_LOW_LATENCY &&
+        params_.frames_per_buffer() != output_params_.frames_per_buffer()) {

[scherkus (not reviewing), 2012/09/17 16:27:23]

doesn't this essentially disable the FIFO when sample rates match?

[no longer working on chromium, 2012/09/17 21:56:28]

True, we should not do this.

+      output_params_.Reset(output_params_.format(),
+                           output_params_.channel_layout(),
+                           output_params_.sample_rate(),
+                           output_params_.bits_per_sample(),
+                           params_.frames_per_buffer());
+    }
+
     // Since the resampler / output device may want a different buffer size than
     // the caller asked for, we need to use a FIFO to ensure that both sides
     // read in chunk sizes they're configured for.
     if (params_.sample_rate() != output_params_.sample_rate() ||
         params_.frames_per_buffer() != output_params_.frames_per_buffer()) {
       DVLOG(1) << "Rebuffering from " << params_.frames_per_buffer()
                << " to " << output_params_.frames_per_buffer();
       audio_fifo_.reset(new AudioPullFifo(
           params_.channels(), params_.frames_per_buffer(), base::Bind(
               &AudioOutputResampler::SourceCallback_Locked,
@@ skipping 171 matching lines @@
     source_callback_->OnError(stream, code);
 }
 
 void AudioOutputResampler::WaitTillDataReady() {
   base::AutoLock auto_lock(source_lock_);
   if (source_callback_ && !outstanding_audio_bytes_)
     source_callback_->WaitTillDataReady();
 }
 
 }  // namespace media