ALSA-LIB: xrun recovery in iec958 plugin for 8ch HDMI?

[Pavel Hofman <pavel.hofman@xxxxxxxxxxx>]

Hi,

Users of RPi's  hdmi:vc4-hdmi report random channel swapping after an 
xrun. Tested (among other clients) on speaker-test, details 
https://forums.raspberrypi.com/viewtopic.php?p=2187582#p2187540

Experienced RPi developer has diagnosed the driver - HDMI device and DMA 
are correctly reset at xrun recovery (i.e. snd_pcm_stop(XRUN) in the 
driver -> snd_pcm_prepare in the client).

Therefore an option is that alsa supplies misaligned 8ch samples after 
the xrun recovery.

Users checked the older HDMI driver bcm2835_audio (bcm2835-pcm.c) which 
accepts standard S16/24_LE formats and does not require the iec958 
plugin and xruns did not cause any channel swaps.

Hence aiming at the iec958 plugin. It seems to keep state (e.g. 
iec->counter) which perhaps may not be reset at snd_pcm_prepare.

Thanks a lot,

Pavel.