Re: Fwd: Odd issue with ALSA connecting directly to HDMI audio output

[Geraldo Nascimento <geraldogabriel@gmail.com>]

On Wed, Jul 19, 2023 at 02:39:44PM +0200, Takashi Iwai wrote:
> On Wed, 19 Jul 2023 14:27:21 +0200,
> Ico Bukvic wrote:
> > 
> > 
> > Thank you, Takashi.
> > 
> > On Raspberry Pi 400 (one with built-in keyboard, although any RPi or Linux
> > computer with HDMI monitor with loudspeakers will do), open pd-l2ork (a
> > variant of pure-data available at http://bit.ly/pd-l2ork; pure-data also has
> > this same problem) and enable DSP. Do the same after changing audio settings
> > via the Preferences window (Edit->Preferences), where you can switch among
> > backends (ALSA vs Portaudio, vs JACK; JACK does not work with any setting). If
> > you have proper audio settings (0 in, 2 out, and a supported SR, r.g.
> > 44,1kHz), you will hear the buzz, and will also hear the desired audio
> > produced (e.g. by running Media->Audio Tester) faintly, with buzz bring at the
> > forefront. Or, you will hear everything OK (default Pulse settings), or
> > nothing. ALSA and PortAudio settings are default Raspbian(RPi)/Ubuntu
> > (desktop). Thank you.
> 
> Well, the question is how the ALSA PCM device is opened, how
> configured and how played.  As Geraldo already suggested, VC4 HDMI on
> RPi has a special format with IEC958 encoding.  Also it has IEC958
> status bit setups.  So, for example, if you'd need to play a normal
> PCM stream with aplay, you'd need to open the device with "hdmi:$CARD"
> device -- then the rest is done in alsa-lib's plugin, and that's
> almost equivalent with what PA does.

Hi Takashi, thanks for taking Ico's report. Perhaps the right
configuration that he needs to use aplay could be:
https://github.com/alsa-project/alsa-lib/blob/master/src/conf/cards/vc4-hdmi.conf

That is, if I understand correctly?

Thanks,
Geraldo Nascimento