[SOLVED] ALSA / Skype / Pulseaudio conflict issue

[dibl]

I've been an occasional audacity user for quite a few years, and was using it for recording as recently as last winter.  I happened to want to open a .wav file in audacity today, and while it appeared to open, the audio was totally nonfunctional.

I went to Edit > Preferences to see whether there was some issue with the non-free libraries, and those buttons are grayed out, so I could not do anything with it.

I do have the most current ffmpeg and lame packages from dmo installed.

Neither google nor the release notes for 2.0.4 were of any help with this issue.

I happen to have a *buntu VM with 2.0.3, and that one works as expected, so I got my work done that way.

This is just FYI -- I don't intend to spend further time trying to fix it since I have the VM to work around the issue.

[seasons]

audacity is not yet compatible with libav 9 and needs to be ported first. Until audacity has been ported, support for some audio formats (AC3, M4A, MP4, WMA) is not available.

http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=692809

[dibl]

Well, maybe ... I don't see .wav listed, but I do have current libav-tools installed.

[seasons]

Well, then that's a different bug. Wav support shouldn't be affected by third-party libraries or lack thereof...

[Gabriel_M]

Audacity does not support file formats owners of Microsoft.
I am a frequent audacity user.
I am converting my audio files to mp3 by using the command:

ffmpeg -i input.wav -f mp3 -ab 192 output.mp3

After using this command I imported the file without problems in Audacity.

[seasons]

WTF are you talking about?

Audacity does not support file formats owners of Microsoft.

Audacity does support .wav files...

I am converting my audio files to mp3

mp3 is patent-encumbered and it's a lossy format (not a good substitute for wav). Why don't you convert to FLAC (or vorbis if you need the disk space)?

[michaa7]

No problems here with Audacity 2.0.4 and .wav (32bit)

[dibl]

A little investigation -- this issue is more subtle than I first thought.  On a second 64-bit siduction system, also KDE, also with both ALSA and Pulseaudio installed, the same audacity version will open and play .wav files.  The File > Preferences > Libraries buttons are also grayed out on that one.

So, it appears to be something about the configuration of my main desktop system, unless it has to do with the driver for the sound chip.

[seasons]

The File > Preferences > Libraries buttons are also grayed out on that one.

That is expected for libav/ffmpeg libs because of the aforementioned bug, but you should have lame available.

[dibl]

I have narrowed down the issue to ALSA, but it is strange. Looking at a .wav file with Dolphin, if I open it with bangarang, kaffeine, or vlc, it will play perfectly.  But if I open it with alsaplayer or audacity, it produces a horribly scratchy "digital" noise.  So I guess I need to get out my ALSA engineering book and see what in the world could be the problem.

[dibl]

I have discovered the problem that caused this issue, and solved it, kinda-sorta.  It's not a pretty situation -- probably there are others who will want to understand it (to the extent that I have it correct).  I guess we can call this "Score 1 for the pulseaudio-haters."  ;-)

1. Skype audio didn't work, and I wanted to fix it.  Googling led me to a solution: in the file /etc/pulse/pa, find the line that reads "load-module module-udev-detect" (line 56 in my current file), and add the following to the end of it:

"tsched=0", so that the edited line reads:

"load-module module-udev-detect tsched=0"

Good news -- this fixes skype audio and it works perfectly, using the "pulse" device.

2. A few days or a week after "fixing" the skype issue, I experienced a problem playing a .wav file with audacity.  At first I thought it was a non-free codecs issue, but eventually I found that nothing that used ALSA was working, although other players such as vlc, kaffeine, and bangarang worked just fine.  Today I made a further investigation, with other KDE systems that I have, and eventually I remembered the above modification that I had made to two different systems in order to use skype.  Upon reversing the modification, ALSA works here again, and skype does not.

So, you can have one of the following, but not both:

-- ALSA and pulseaudio and all sound apps except skype working

-- pulseaudio and skype working, but no ALSA apps

or else ALSA only, and whatever non-pulseaudio combination of packages that you can get working.


I have marked this one solved, and changed the title to better reflect the real issue.

[dibl]

Today from arch forums I learned that the skype audio problem can be resolved by launching it with

Code Select Expand


env PULSE_LATENCY_MSEC=30 skype %U

With this option, the "tsched=0" modification in /etc/pulse/default.pa is not necessary, and ALSA is not impacted.