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, 4 insertions, 0 deletions

diff --git a/media/audio/linux/alsa_wrapper.h b/media/audio/linux/alsa_wrapper.h
index d7686dd..5ab3c84 100644
--- a/media/audio/linux/alsa_wrapper.h
+++ b/media/audio/linux/alsa_wrapper.h
@@ -15,6 +15,10 @@ class AlsaWrapper {
   AlsaWrapper();
   virtual ~AlsaWrapper();
 
+  virtual int DeviceNameHint(int card, const char* iface, void*** hints);
+  virtual char* DeviceNameGetHint(const void* hint, const char* id);
+  virtual int DeviceNameFreeHint(void** hints);
+
   virtual int PcmOpen(snd_pcm_t** handle, const char* name,
                       snd_pcm_stream_t stream, int mode);
   virtual int PcmClose(snd_pcm_t* handle);