Re: [gentoo-user] ALSA wizard...

[Mark Knecht <markknecht@gmail.com>]

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On Sun, Apr 26, 2020 at 12:09 PM Jorge Almeida <jjalmeida@gmail.com> wrote:
>
> On Sun, Apr 26, 2020 at 5:58 PM Mark Knecht <markknecht@gmail.com> wrote:
> >
> >
> >
> Mark,
>
> I recompiled the kernel with more stuff as module, but I just had an
> idea to make sure the Behringer is the only card in the game: I
> disabled HD audio in the firmware settings. So: both Opera and Chrome
> play Youtube. aplay plays music files just fine, as it did before.
> Audacious also works (it requires modifying the former settings;
> that's probably what was missing before). So, I would say everything
> works, except stuff like discord. To my shame, I didn't check the logs
> with enough attention: it says:
>
> [000:000] [5256] (audio_device_pulse_linux.cc:1547): failed to load
symbol table
> [000:000] [5256] (audio_device_pulse_linux.cc:145): failed to
> initialize PulseAudio
> [000:000] [5256] (audio_device_impl.cc:377): Audio device initialization
failed.
>
> (To my defence: the ebuild does't try to pull pulseaudio; one would
> assume that it would be a dependency)
>
> Hence: no mystery at all, just the usual with linux nowadays.
>
> I'll keep searching for some audio chat package that works. mumble
> seems promising, but it requires an available server. zoom (which most
> people @work use) doesn't emerge. slack does emerge and vomits a
> totally unresponsive window (well, not *totally* unresponsive: Ctrl+Q
> works :))
>
> Since you use pulseaudio (per your latest post): can you send the
> contents of a wav file to an external DAC via toslink, without
> pulseaudio messing with the file? (Most people don't seem to care
> whether the signal is first converted to analog, and resampled, and
> converted to digital, and whatnot, before leaving the computer...)
>
> I appreciate the enormous amount of effort you put on this.
> Thanks
>
> Jorge

I'll investigate what I can do sending files by hand. However on the USB
only machine all the internal sound card hardware is blacklisted so modules
aren't loaded. I don't know that I want to upset the environment on that
machine very much but a bit more about this at the bottom of this post.

A bit of extra info:

<SNIP>
> First, I have only 1 card, the Focusrite Scarlett. Keep in mind I'm using
Kubuntu (KDE) and there is pulseaudio installed. I do not know what role
pulseaudio is playing in my sound stack but I assume it's involved.
<SNIP>

pavucontrol-qt (in KDE) gives me a clear view of what pulseaudio is doing,
in case you find out it's installed and running on your system. You
probably don't have the qt version on a non-KDE system I suspect.

I am tending to trust this link for a description of pulseaudio's purpose.

https://superuser.com/questions/144648/how-do-alsa-and-pulseaudio-relate

It provides a horizontal VU meter corresponding to what an application is
producing.

The description seems consistent with Matt's earlier post. Essentially in
the old days Alsa itself could only handle one application's audio on each
(logical) channel of a given card. This meant you couldn't run two audio
apps at the same time unless you mixed the audio in a mixer outside of the
machine. The original solution for this problem - say you're playing a CD
but want to hear system sounds also - was (I believe) dmix but it was
difficult to use for the average desktop user. Anyway, after some time
pulseaudio came along as a means of automatically combining lots of
software sound sources into a single stream that goes to whatever card you
want it to go to. On paper anyway it supports Alsa, Jack and OSS as the
underlying audio hardware target and mixes any sound sources that know how
to talk to pulseaudio.

On my big machine I have a lot more audio hardware enabled:

(base) mark@science:~$ cat /proc/asound/cards
0 [DSP            ]: H-DSP - Hammerfall DSP
                     RME Hammerfall HDSP 9652 at 0xfbef0000, irq 16
1 [Intel          ]: HDA-Intel - HDA Intel
                     HDA Intel at 0xf9ff8000 irq 37
2 [NVidia         ]: HDA-Intel - HDA NVidia
                     HDA NVidia at 0xfb9fc000 irq 38
(base) mark@science:~$

On this machine all KDE audio (notifications, youtube, vlc, whatever) goes
to card 1, the HDA Intel motherboard device. card 0 is 'disabled' in KDE
but has Alsa drivers loaded (obviously - it's in the list above) so I can
talk to it directly with Mixbus. Essentially KDE and pulseaudio don't even
know it's there. My outboard DAC is attached to the HDSP spdif port. KDE
audio goes out the headphone port and back into the machine through an 8
channel outboard ADC and is 'mixed' in the HDSP with audio created in my
'creative' environment. There's a bit of extra latency (50ms) doing it this
way but it works great. On this machine I'm pretty much free to play with
virtual cards and the like which I might do.

Anyway, last thing for now would be that I'm still willing and slightly
interested in looking at discord/zoom/whatever for my own needs. If I make
some headway, or if you want to collaborate in that area let me know,
either through gentoo-user of privately.

Cheers,
Mark

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