Enable low latency mode for audio playback on Android

Enable low latency mode for audio playback on Android

On Android, in order to use low latency mode for audio playback, it's required to use exact sampling rate and buffer size queried from the device.
This patch uses 2048 frames for IPC buffer and native size (queried from device) for buffer sent to the device.

BUG=243506
TEST=run https://apprtc.appspot.com/?debug=loopback on Google Android devices, e.g., Galaxy Nexus, Nexus4. The audio quality is much better than the exisiting setup.
R=dalecurtis@chromium.org

Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=206821

[wjia(left Chromium), 2013-06-17 21:41:03]

I'd move forward with this simple patch first to enable low latency audio
playback on Android. This patch uses native buffer size (queried from device) to
send frames to the device. IPC buffer size is set to 2048. Hopefully we have an
agreement on this front.

Regarding the rest change, I'd defer it to the future.

[DaleCurtis, 2013-06-17 21:49:08]

lgtm % adding a TEST= line to the description with some discussion on how this
sounds and your testing method.

[DaleCurtis, 2013-06-17 21:49:53]

https://chromiumcodereview.appspot.com/17209003/diff/4001/media/audio/android...
File media/audio/android/audio_manager_android.cc (left):

https://chromiumcodereview.appspot.com/17209003/diff/4001/media/audio/android...
media/audio/android/audio_manager_android.cc:129: // Return the optimal size as
a multiple of the low latency frame
Also delete this comment and just return  GetAudioLowLatencyOutputFrameSize();
directly too.

[wjia(left Chromium), 2013-06-17 22:04:09]

Thanks!

https://chromiumcodereview.appspot.com/17209003/diff/4001/media/audio/android...
File media/audio/android/audio_manager_android.cc (left):

https://chromiumcodereview.appspot.com/17209003/diff/4001/media/audio/android...
media/audio/android/audio_manager_android.cc:129: // Return the optimal size as
a multiple of the low latency frame
On 2013/06/17 21:49:53, DaleCurtis wrote:
> Also delete this comment and just return  GetAudioLowLatencyOutputFrameSize();
> directly too.

Done.

[DaleCurtis, 2013-06-17 22:05:12]

Make sure you test a WebAudio demo too.

[wjia(left Chromium), 2013-06-17 22:55:33]

Committed patchset #3 manually as r206821 (presubmit successful).