On Sun, Jul 26, 2020 at 11:32 PM Samuel Sieb <samuel@sieb.net> wrote:

> mythtv@seveneves ~]$ amixer -c0 scontrols
> Simple mixer control 'PCM',0
> Simple mixer control 'PCM Capture Source',0
> Simple mixer control 'PCM',1
> Simple mixer control 'PCM',2

Maybe I should have asked for the more verbose option.  It's probably
one of these.

mythtv@seveneves ~]$ amixer -c0 controls
numid=10,iface=CARD,name='Clock Source 21 Validity'
numid=15,iface=CARD,name='Clock Source 22 Validity'
numid=18,iface=CARD,name='Clock Source 23 Validity'
numid=30,iface=CARD,name='Clock Source 24 Validity'
numid=35,iface=CARD,name='Clock Source 25 Validity'
numid=16,iface=CARD,name='Headphone - Output Jack'
numid=19,iface=CARD,name='IEC958 In - Output Jack'
numid=36,iface=CARD,name='Keep Interface'
numid=24,iface=CARD,name='Line - Input Jack'
numid=20,iface=CARD,name='Mic - Input Jack'
numid=31,iface=CARD,name='Mic - Input Jack',index=1
numid=11,iface=CARD,name='Speaker - Output Jack'
numid=7,iface=MIXER,name='PCM Playback Switch'
numid=12,iface=MIXER,name='PCM Playback Switch',index=1
numid=17,iface=MIXER,name='PCM Playback Switch',index=2
numid=8,iface=MIXER,name='PCM Playback Volume'
numid=13,iface=MIXER,name='PCM Playback Volume',index=1
numid=29,iface=MIXER,name='PCM Capture Source'
numid=27,iface=MIXER,name='PCM Capture Switch'
numid=28,iface=MIXER,name='PCM Capture Volume'
numid=25,iface=MIXER,name='Line Capture Switch'
numid=26,iface=MIXER,name='Line Capture Volume'
numid=21,iface=MIXER,name='Mic Capture Switch'
numid=32,iface=MIXER,name='Mic Capture Switch',index=1
numid=22,iface=MIXER,name='Mic Capture Volume'
numid=33,iface=MIXER,name='Mic Capture Volume',index=1
numid=23,iface=MIXER,name='Auto Gain Control'
numid=34,iface=MIXER,name='Auto Gain Control',index=1
numid=9,iface=MIXER,name='Input Gain Pad Control'
numid=14,iface=MIXER,name='Input Gain Pad Control',index=1
numid=5,iface=PCM,name='Capture Channel Map'
numid=1,iface=PCM,name='Playback Channel Map'
numid=6,iface=PCM,name='Capture Channel Map',device=1
numid=2,iface=PCM,name='Playback Channel Map',device=1
numid=3,iface=PCM,name='Playback Channel Map',device=2
numid=4,iface=PCM,name='Playback Channel Map',device=3

I wanted to use "cset ... unmute", because the iec958 device seems to be muted by default sometimes, but I couldn't figure out how to specify that control. The amixer man page says:

 cset <CONTROL> <PARAMETER> ...
              Sets  the card control contents. The identifier has these compo‐
              nents: iface, name, index, device, subdevice,  numid.  The  next
              argument specifies the value of control.
 
...but I couldn't figure out correct values for all these components. My attempts always got:

[mythtv@seveneves ~]$ amixer cset numid=19,iface=CARD,name='IEC958 In - Output Jack' unmute
amixer: Cannot find the given element from control default


 > $ aplay -D iec958:CARD=SoundCard,DEV=0

Add "-vv" or "-vvv" to the command to be able to tell if it's actually
sending something.  Also, try this command with "DEV=1" as well. 

Using DEV=1, I get:

 [mythtv@seveneves ~]$ aplay -vv -D iec958:CARD=SoundCard,DEV=1 /pub/flac/music/rock/CDs/Country_Joe/CollectedCountryJoe/CCJatFT05.wav
aplay: main:830: audio open error: No such file or directory

Using -vv on the DEV=0 version does show the "meter" with the pound signs bouncing up and down, so it thinks it's sending something. But the optical cable is not lit. I did check the obvious and the stupid, and it does appear to be fully seated into the card. While I was at it, I also tried using a different optical cable that I know is good, but still no sound.

If you
still don't hear anything, then run alsamixer and turn up all of those
PCM outputs and try both of them again.

Turning them all up in alsamixer was the first thing I tried. They are all maxed out.
 

It's strange that pulseaudio and ALSA know about the digital output, but
you can't select it. 

That is not an encouraging sign, but I have learned more about how this stuff works from this conversation than I ever knew before, so there is a lot I don't know.
 
Something that I should have asked earlier though
is whether or not the optical cable is lit up.

Funny, I thought of this as I was going to sleep last night. I guess it's evidence that I spent too much time on this yesterday and got too frustrated; my brain was not working very well. I should have thought of that much earlier.

--Greg