ao_coreaudio: do not accept unknown channel layouts

Coreaudio gives us a channel map with all entries set to
kAudioChannelLabel_Unknown. This is translated to a mpv channel map with
all channels set to NA, which has special meaning: it's an "unknown"
channel map, which acts as wildcard and can be converted from/to any
channel layout. Not really what we want.

I've got this with USB audio, playing stereo. The multichannel layout
consisted of 2 unknown channels, while the stereo channel map was
stereo (as expected).

Note that channel maps with _some_ NA entries are not affected by this,
and must still work.

0 files changed, 0 insertions, 0 deletions