Use larger buffer sizes for lower power on Linux.

media/audio/cras/audio_manager_cras.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/cras/audio_manager_cras.h"
 
 #include "base/command_line.h"
 #include "base/environment.h"
 #include "base/logging.h"
 #include "base/nix/xdg_util.h"
@@ skipping 12 matching lines @@
       AudioDeviceName(AudioManagerBase::kDefaultDeviceName,
                       AudioManagerBase::kDefaultDeviceId));
 }
 
 // Maximum number of output streams that can be open simultaneously.
 static const int kMaxOutputStreams = 50;
 
 // Default sample rate for input and output streams.
 static const int kDefaultSampleRate = 48000;
 
+// Define bounds for the output buffer size.
+static const int kMinimumOutputBufferSize = 512;
+static const int kMaximumOutputBufferSize = 8192;
+
 bool AudioManagerCras::HasAudioOutputDevices() {
   return true;
 }
 
 bool AudioManagerCras::HasAudioInputDevices() {
   return true;
 }
 
 AudioManagerCras::AudioManagerCras(AudioLogFactory* audio_log_factory)
     : AudioManagerBase(audio_log_factory) {
@@ skipping 53 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 AudioManagerCras::GetPreferredOutputStreamParameters(
     const std::string& output_device_id,
     const AudioParameters& input_params) {
   // TODO(tommi): Support |output_device_id|.
   DLOG_IF(ERROR, !output_device_id.empty()) << "Not implemented!";
-  static const int kDefaultOutputBufferSize = 512;
-
   ChannelLayout channel_layout = CHANNEL_LAYOUT_STEREO;
   int sample_rate = kDefaultSampleRate;
-  int buffer_size = kDefaultOutputBufferSize;
+  int buffer_size = kMinimumOutputBufferSize;
   int bits_per_sample = 16;
   int input_channels = 0;
   if (input_params.IsValid()) {
     sample_rate = input_params.sample_rate();
     bits_per_sample = input_params.bits_per_sample();
     channel_layout = input_params.channel_layout();
     input_channels = input_params.input_channels();
-    buffer_size = input_params.frames_per_buffer();
+    buffer_size =
+        std::min(kMaximumOutputBufferSize,
+                 std::max(buffer_size, input_params.frames_per_buffer()));
   }
 
   int user_buffer_size = GetUserBufferSize();
   if (user_buffer_size)
     buffer_size = user_buffer_size;
 
   return AudioParameters(
       AudioParameters::AUDIO_PCM_LOW_LATENCY, channel_layout, input_channels,
       sample_rate, bits_per_sample, buffer_size, AudioParameters::NO_EFFECTS);
 }
@@ skipping 17 matching lines @@
     case 24:
       return SND_PCM_FORMAT_S24;
     case 32:
       return SND_PCM_FORMAT_S32;
     default:
       return SND_PCM_FORMAT_UNKNOWN;
   }
 }
 
 }  // namespace media