"Unknown PCM" issue with LADSPA? Here's a solution!

voidzero · Bodhisattva Joined: 21 Jul 2002 Posts: 265 Location: Grnn

I was having issues with my LADSPA config. I'm using alsa (1.0.25-r1) and pulseaudio (2.1-r1).

In short - I was able to use my own PCM devices, set in ~/.asoundrc, as root, but not as a normal user. Even though I had already added the user into the audio group, when I tried something like speaker-test -c2 -Dladspa, I always got an error that said something like Unknown PCM ladspa; Playback open error: -17 File exists.

After a lot of trial and error (which felt like searching for a needle in a haystack), I solved this issue as follows. It seems that ~/.asoundrc (as well as /etc/asound.conf) is being loaded twice: once by /usr/share/alsa/alsa.conf and once by /usr/share/alsa/alsa.conf.d/51-pulseaudio-probe.conf.

As I said, I'm using pulseaudio, so I ended up editing /usr/share/alsa/alsa.conf and I commented line 19, which now contains #~/.asoundrc. Now it'll just be loaded once which is how it should be - no more File exists error.

This was enough to get my LADSPA PCMs to work again. Yay! I'm sharing this titbit of info lest anyone else who faces this problem has to go through the same boring trial-and-error search routine as I had to just now.

*Edit* this bug seems to be fixed on newer versions.
_________________
Diplomacy is the art of letting the other party have things your way.
-- Daniele Vare

voidzero · Bodhisattva Joined: 21 Jul 2002 Posts: 265 Location: Grnn

So... no one else experienced this issue?
_________________
Diplomacy is the art of letting the other party have things your way.
-- Daniele Vare

MiaoRenFeng · n00b Joined: 10 Feb 2015 Posts: 1

It is 2015 now, having this same issue in Debian stable "Wheezy" and yet this worked like a charm.
I guess stable uses really old versions (alsa 1.0.25+3~deb7u1)

Thanks a lot for documenting this here.

Cheers.

_________________
-Somewhere in time

voidzero · Bodhisattva Joined: 21 Jul 2002 Posts: 265 Location: Grnn

steveL · Posted: Wed Feb 11, 2015 10:05 am Post subject:

Well, I'm glad this got bumped as I never even knew about /usr/share/alsa let alone the myriad amount of settings being configured under there.

WTF? When did we go to having conf in /usr/share of all places?

Anyhow, thanks, now I know where to look for the sound snafus..