ao_alsa: try to fallback to "default" device if device is busy

ALSA is crap. It's impossible to make multichannel playback just do the
right thing. dmix (the default on most distros) can do stereo only, and
will refuse to play multichannel. On the other hand, if you try like mpv
(and mplayer) to open a multichannel device (like "surround51" etc.),
this will actually open a hardware device, which will either fail if
dmix is active, or block out dmix if opening succeeds.

This commit falls back to "default" (i.e. dmix) if opening a
multichannel device fails, which is a tiny step towards the right
behavior. (Although fixing it fully is impossible.)

1 files changed, 6 insertions, 1 deletions

diff --git a/audio/out/ao_alsa.c b/audio/out/ao_alsa.c
index 4e54f161fe..efa32e46e3 100644
--- a/audio/out/ao_alsa.c
+++ b/audio/out/ao_alsa.c
@@ -461,17 +461,22 @@ static int init(struct ao *ao)
         if (strcmp(device, "default") != 0)
             device = talloc_asprintf(ao, "plug:%s", device);
     }
+    const char *old_dev = device;
     if (ao->device)
         device = ao->device;
     if (p->cfg_device && p->cfg_device[0])
         device = p->cfg_device;
+    bool user_set_device = device != old_dev; // not strcmp()
 
     MP_VERBOSE(ao, "using device: %s\n", device);
     MP_VERBOSE(ao, "using ALSA version: %s\n", snd_asoundlib_version());
 
     err = try_open_device(ao, device, p->cfg_block ? 0 : SND_PCM_NONBLOCK);
     if (err < 0) {
-        if (err != -EBUSY && !p->cfg_block) {
+        if (err == -EBUSY && !user_set_device && strcmp(device, "default") != 0) {
+            MP_WARN(ao, "Device '%s' busy, retrying default.\n", device);
+            err = try_open_device(ao, "default", 0);
+        } else if (err != -EBUSY && !p->cfg_block) {
             MP_WARN(ao, "Open in nonblock-mode "
                     "failed, trying to open in block-mode.\n");
             err = try_open_device(ao, device, 0);