iec61937: force hw_param channels to stereo

In case of pass-through, iec frames are sent over a stereo PCM
stream. So alsa device should be configured with channels = 2.
This is needed to be compatible with SPDIF electrical/optical output
that supports only stereo in PCM mode and up to 8 channels in iec61937 mode.

Signed-off-by: Arnaud Pouliquen <arnaud.pouliquen@st.com>
1 file changed