Hi!
I just noticed while testing the ALSA HDMI channel remapping code that my NVIDIA codec 0x10de0015 does not seem to follow the Audio Sample Packet (ASP) channel mapping (set by verb F34h as per HDA spec 7.3.3.41) when playing back stereo audio.
This can be reproduced by e.g.: $ speaker-test -c2 -Dhdmi:CARD=NVidia,DEV=0 -m FR,FL The channels are reversed compared to what the printout is (i.e. the codec plays the streams straight-through instead of swapping channels as instructed).
E.g. this works expectedly, however: $ speaker-test -c4 -Dhdmi:CARD=NVidia,DEV=1 -m FR,FL,RR,RL
(note that recent sound git master or for-next is needed for these kind of remappings to work properly at all)
On Intel HDMI codec 0x80862806 both work.
While stereo right-left swapping is admittedly a rather corner-case situation, I guess we should probably refuse such chmaps when they are not supported.
Aaron, do you have any information on whether this affects all NVIDIA HDMI codecs?