audio_manager_linux: Allow CRAS to decide if sample rate conversion is needed.

media/audio/linux/audio_manager_linux.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/linux/audio_manager_linux.h"
 
 #include "base/command_line.h"
 #include "base/environment.h"
 #include "base/logging.h"
 #include "base/nix/xdg_util.h"
@@ skipping 333 matching lines @@
 }
 
 AudioParameters AudioManagerLinux::GetPreferredLowLatencyOutputStreamParameters(
     const AudioParameters& input_params) {
   // Since Linux doesn't actually have a low latency path the hardware buffer
   // size is quite large in order to prevent glitches with general usage.  Some
   // clients, such as WebRTC, have a more limited use case and work acceptably
   // with a smaller buffer size.  The check below allows clients which want to
   // try a smaller buffer size on Linux to do so.
   int buffer_size = 0;
   if (static_cast<size_t>(input_params.frames_per_buffer()) <

[DaleCurtis, 2012/09/25 19:56:55]

Mind collapsing this to:

int buffer_size = GetAudioHardwareBufferSize();
if (input_params.frames_per_buffer() < buffer_size)
  buffer_size = input_params.frames_per_buffer();

While you're here?

       GetAudioHardwareBufferSize()) {
     buffer_size = input_params.frames_per_buffer();
   } else {
     buffer_size = GetAudioHardwareBufferSize();
   }
 
+#if defined(USE_CRAS)
+  // CRAS will sample rate convert if it is needed, pass the desired frame rate.

[DaleCurtis, 2012/09/25 19:56:55]

To keep style with the above code, why not:

int sample_rate = GetAudioHardwareSampleRate();
if (UseCras())
  sample_rate = input_params.sample_rate();

I don't think the IF_DEF is necessary since UseCras is always defined and
returns false in non-cras case.

+  if (UseCras())
+    return AudioParameters(
+        AudioParameters::AUDIO_PCM_LOW_LATENCY, input_params.channel_layout(),
+        input_params.sample_rate(), 16, buffer_size);
+#endif
+
   // TODO(dalecurtis): This should include bits per channel and channel layout
   // eventually.
   return AudioParameters(
       AudioParameters::AUDIO_PCM_LOW_LATENCY, input_params.channel_layout(),
       GetAudioHardwareSampleRate(), 16, buffer_size);
 }
 
 }  // namespace media