Use larger buffer sizes for lower power on Linux.

media/audio/pulse/audio_manager_pulse.cc

 // Copyright 2013 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/pulse/audio_manager_pulse.h"
 
 #include "base/command_line.h"
 #include "base/environment.h"
 #include "base/files/file_path.h"
 #include "base/logging.h"
@@ skipping 17 matching lines @@
 #endif  // defined(DLOPEN_PULSEAUDIO)
 
 namespace media {
 
 using pulse::AutoPulseLock;
 using pulse::WaitForOperationCompletion;
 
 // Maximum number of output streams that can be open simultaneously.
 static const int kMaxOutputStreams = 50;
 
+// Define bounds for the output buffer size.
+static const int kMinimumOutputBufferSize = 512;
+static const int kMaximumOutputBufferSize = 8192;
+
 static const base::FilePath::CharType kPulseLib[] =
     FILE_PATH_LITERAL("libpulse.so.0");
 
 // static
 AudioManager* AudioManagerPulse::Create(AudioLogFactory* audio_log_factory) {
   scoped_ptr<AudioManagerPulse> ret(new AudioManagerPulse(audio_log_factory));
   if (ret->Init())
     return ret.release();
 
   DVLOG(1) << "PulseAudio is not available on the OS";
@@ skipping 106 matching lines @@
     const AudioParameters& params, const std::string& device_id) {
   DCHECK_EQ(AudioParameters::AUDIO_PCM_LOW_LATENCY, params.format());
   return MakeInputStream(params, device_id);
 }
 
 AudioParameters AudioManagerPulse::GetPreferredOutputStreamParameters(
     const std::string& output_device_id,
     const AudioParameters& input_params) {
   // TODO(tommi): Support |output_device_id|.
   VLOG_IF(0, !output_device_id.empty()) << "Not implemented!";
-  static const int kDefaultOutputBufferSize = 512;
 
   ChannelLayout channel_layout = CHANNEL_LAYOUT_STEREO;
-  int buffer_size = kDefaultOutputBufferSize;
+  int buffer_size = kMinimumOutputBufferSize;
   int bits_per_sample = 16;
   int input_channels = 0;
   int sample_rate;
   if (input_params.IsValid()) {
     bits_per_sample = input_params.bits_per_sample();
     channel_layout = input_params.channel_layout();
     input_channels = input_params.input_channels();
-    buffer_size = std::min(buffer_size, input_params.frames_per_buffer());
+    buffer_size =
+        std::min(kMaximumOutputBufferSize,
+                 std::max(buffer_size, input_params.frames_per_buffer()));
     sample_rate = input_params.sample_rate();
   } else {
     sample_rate = GetNativeSampleRate();
   }
 
   int user_buffer_size = GetUserBufferSize();
   if (user_buffer_size)
     buffer_size = user_buffer_size;
 
   return AudioParameters(
@@ skipping 140 matching lines @@
 void AudioManagerPulse::SampleRateInfoCallback(pa_context* context,
                                                const pa_server_info* info,
                                                void* user_data) {
   AudioManagerPulse* manager = reinterpret_cast<AudioManagerPulse*>(user_data);
 
   manager->native_input_sample_rate_ = info->sample_spec.rate;
   pa_threaded_mainloop_signal(manager->input_mainloop_, 0);
 }
 
 }  // namespace media