ao_oss: Fallback to stereo when the device does not support >2 channels

ioctl(..., SNDCTL_DSP_CHANNELS, &nchannels) for not supported
nchannels does not return an error and instead set nchannels to
the default value.

Instead of failing with no audio, fallback to stereo.

1 files changed, 10 insertions, 6 deletions

diff --git a/audio/out/ao_oss.c b/audio/out/ao_oss.c
index f037812e70..4a1e483cfb 100644
--- a/audio/out/ao_oss.c
+++ b/audio/out/ao_oss.c
@@ -336,19 +336,23 @@ static int reopen_device(struct ao *ao, bool allow_format_changes)
             mp_chmap_sel_add_map(&sel, &oss_layouts[n]);
         if (!ao_chmap_sel_adjust(ao, &sel, &channels))
             goto fail;
-        int reqchannels = channels.num;
+        int c, nchannels, reqchannels;
+        nchannels = reqchannels = channels.num;
         // We only use SNDCTL_DSP_CHANNELS for >2 channels, in case some drivers don't have it
         if (reqchannels > 2) {
-            int nchannels = reqchannels;
-            if (ioctl(p->audio_fd, SNDCTL_DSP_CHANNELS, &nchannels) == -1 ||
-                nchannels != reqchannels)
-            {
+            if (ioctl(p->audio_fd, SNDCTL_DSP_CHANNELS, &nchannels) == -1) {
                 MP_ERR(ao, "Failed to set audio device to %d channels.\n",
                        reqchannels);
                 goto fail;
             }
+            if (nchannels != reqchannels) {
+                // Fallback to stereo
+                nchannels = 2;
+                goto stereo;
+            }
         } else {
-            int c = reqchannels - 1;
+stereo:
+            c = nchannels - 1;
             if (ioctl(p->audio_fd, SNDCTL_DSP_STEREO, &c) == -1) {
                 MP_ERR(ao, "Failed to set audio device to %d channels.\n",
                        reqchannels);