Move Alsa device opening into the audio thread, and add in support for multi-channel audio.

Moving the device opening into the audio thread will prevent browser hangs for badly behaving alsa implementations (like pulseaudio) that can hang snd_pcm_open if pulseaudiod is wedged, even if SND_PCM_NONBLOCK is requested.

For multi-channel audio, device enumeration has been added to try and find a multi-channel device with a stable channel mapping.  According to http://0pointer.de/blog/projects/guide-to-sound-apis.html, default should only be used with mono and stereo stream because the channel ordering is not defined by Alsa. To get a well-defined channel ordering, one must use one of the surround40, surround51, etc., device names.  However, these device names do not always allow multiple opens, so a fallback scheme is implemented to use default if necessary.

BUG=20945,17703
TEST=listened with built-in soundcard and USB soundcard with various other audio programs running.

Review URL: http://codereview.chromium.org/275022

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@29299 0039d316-1c4b-4281-b951-d872f2087c98

1 files changed, 1 insertions, 2 deletions

diff --git a/media/audio/mac/audio_output_mac.cc b/media/audio/mac/audio_output_mac.cc
index a8f34f3..42e80a1 100644
--- a/media/audio/mac/audio_output_mac.cc
+++ b/media/audio/mac/audio_output_mac.cc
@@ -171,7 +171,7 @@ void PCMQueueOutAudioOutputStream::GetVolume(double* left_level,
 // TODO(fbarchard): Switch layout when ffmpeg is updated.
 namespace {
 template<class Format>
-static void SwizzleLayout(Format *b, size_t filled) {
+static void SwizzleLayout(Format* b, size_t filled) {
   static const int kNumSurroundChannels = 6;
   Format aac[kNumSurroundChannels];
   for (size_t i = 0; i < filled; i += sizeof(aac), b += kNumSurroundChannels) {
@@ -274,4 +274,3 @@ void PCMQueueOutAudioOutputStream::Start(AudioSourceCallback* callback) {
     return;
   }
 }
-