vc4.ko brings unusable&unstable ALSA sinks

[Diederik de Haas]

Hi,

On dinsdag 30 maart 2021 03:22:55 CEST Ryutaroh Matsumoto wrote:
> sorry for my emails not being much helpful...

They are helpful, they just didn't result in a working audio. There's also 
frustration on my side, which may have resulted in a wrong tone.

> > In both cases mpd started playing but I heard nothing.
> > diederik at rpi-mpd:~$ aplay -l
> > diederik at rpi-mpd:~$ pactl list cards
> 
> It should work... At least I had no problem under similar situations...
> vc4.ko's HDMI audio output works fine with my RPi4B,
> but I am not very sure if vc4.ko works with HDMI audio of your RPi3.

That's indeed another one of those variables. The RPi4 is (importantly) 
different from the RPi3 (and earlier models).
In other configs I got all kinds of error msgs or mpd refused to start playing.
Now I get no error msgs and mpd starts playing. The only thing missing is the 
actual sound itself, which is also important ;-P

> My weak suggestions are
> (1) module_blacklist=vc4 if you don't need it... Or

IIRC that did work, but only for stereo sound, not multi-channel audio. As I 
want the device to handle all audio, including from Kodi (films/TV shows), the 
latter is important to me.
Maybe I'll give it another try.

> (2) Comment out load-module module-udev-detect and load-module module-detect
> from /etc/pulse/default.pa, and add
> load-module module-alsa-card device_id=number,
> where "number" is the card number of snd_bcm2835.ko found in
> /proc/asound/cards.
> 
> For (2), I found that vc4.ko's HDMI audio does not work with
> "module-alsa-sink" in default.pa... "module-alsa-card" works...

That's an important clue, thanks :)

> Raspberry Pi OS kernel latest version now works fine with pulseaudio.

Is that a 32bit or 64bit kernel? AFAIK, all the problems are with 64bit.
Unfortunately Debian isn't going to support 32bit for the RPi3B+, but I might 
even resort to compiling my own kernel (minimal patch set on top of Debian's).
But I really prefer not to.

> Their solution is to completely disable HDMI audio output of snd_bcm2835.ko,
> and only vc4.ko's HDMI audio is used and enabled by them.

I'm not interested in audio via the 'headphone jack', I want to use the HDMI 
cable to transfer the audio. I guess, but don't know for sure, if that's the 
same as HDMI audio.
It can/could output video as well, but the system is setup to be run headless, 
hence system-wide pulseaudio.
I previously asked what the role/purpose was of vc4hdmi, but got no answer.
So I don't know if I should use one OR the other or that they're supposed to 
work together in 'some' way.
Only using vc4hdmi looks the most promising ... but I still want to actually 
hear sounds ;)

> I hope the above is useful...

Yes, thanks.

> ... I probably found all the workaround ... They are summarized at
> https://github.com/emojifreak/debian-rpi-image-script#comments-on-linux-510-> and-rapsberry-pi-4-as-of-march-2021 

Thanks, I'll take a look.

> Best regards, Ryutaroh

Cheers,
  Diederik
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