Skipping during playback and record

[dlowerre]

I am very sad and frustrated.

I used to be able to play back audio and record at the same time (with play-thru turned OFF) without any skipping.

Now no matter what I try I get skips during recording.

My test setup is to import some raw audio, and just start recording. Eventually I hear the audio skip. If I go back and listen to the recording, there are audible gaps.

This used to work so well, and I have no Idea what I did to break it or how to get it back into working form. That is because there are so many options for Playback and Recording that it is almost impossible to find out what is not set right. I even tried removing the old .cfg file so that the program would go back to the defaults. Unfortunately this did not fix my problem.

I re-installed all of the ALSA packages using synaptic.

I re-installed audacity as well.

I would de-frag the disk but I am using Ubuntu and the consensus online is that there is no good reason to defrag a disk in Linux.

I set the 'NICE' value of Audacity to -20 but the problem happens anyway. I set the recording rate to 16K, with 16bit samples. Still the same problem.

I am using a Toshiba Laptop. Is it possible that the recording hardware has degraded in some way?

I did search this forum for a fix, honest, but I could not find a thread with a solution. Can anyone provide me with a link to a solution?

[steve]

Some things to check:

Before changing any of these settings, write down on paper the current settings - getting these settings right on Linux can be a pain in the A.

"Edit menu > Preferences Quality"

Default Sample Rate: either 44100 or 48000 do not go higher than 48000

Default Sample Format: try 16 bit (if we get Audacity running better with other changes, you can then try changing this to a 32 bit).

Real Time Conversion: Fast / None.

View Menu
Switch off "Show Clipping"


Watch out for the Ubuntu "Update Manager" - If your system is checking for updates, Audacity will slow right down.

Any improvement so far?
Be careful with this one and definitely write down the current settings:
"Edit menu > Preferences > Audio I/O"
Do you have "Alsa default" listed in the playback and recording devices? If it is listed, then select it.
If Alsa default is not available, exit from Audacity, and the shut down "pulseaudio", then restart Audacity - you should now have "ALSA default" available.

I hope something in there helps.

[dlowerre]

I am apparently way behind version-wise because some of the choices you mention are not available to me.

I am running 1.3.3 from the Ubuntu library. Perhaps I should upgrade to the latest beta?

BTW: My audio i/o settings were as you specified, so no improvement there.

I do not have a 'show clipping' option to turn off.

Finally: Alsa Default is available for both recording and playback. I have Alsa Default set for playback, but
I have ALSA Front selected for recording. When I try to use ALSA Default for recording, Audacity hangs
when I hit the record button. The System Monitor shows it gobbling up CPU but nothing ever gets recorded
and the whole interface freezes.

Oh and thanks for replying. I have seen a lot of your activity on this site and I am really impressed by how
helpful you are.

[steve]

Shutting down pulseaudio may be worth trying - it seems to make quite a bit of difference on my machine.

Regards upgrading, the best version so far on my Ubuntu box is Audacity 1.3.8 alpha
How do you feel about building from the cvs source? I'm no expert, but once you get all of the dependencies sorted out it is pretty straightforward. There's a write up in the Linux section of the forum that outlines most of the procedure - come to think of it, this post should really be in the Linux section.

[dlowerre]

Well, pulseaudio is definitely not the problem as I am running Gutsy.

Which might also be the problem, but this was working for me so well for so long.

I tried 1.3.4 using gutsy backports, but it was far worse.

[dlowerre]

My recap is as follows:

I grabbed an old ibm thinkpad that I have that only has 256mb ram, wiped the XP virus off it and installed xubuntu.

I then installed Audacity using Add/Remove and got 1.3.4

I had to run alsamixer from the console to get turn on and off the correct capture channels but everything worked and now I am able to play back and record at the same time on a machine that is far weaker than the one I was using previously.

Also, the benchmark fails on my newer machine.

So, I think my sound hardware is broken. I think that the sound device itself fails occasionaly when both the DAC and ADC are operating. When either is the only one working at a time they work fine. But playback during record is too useful to do without.

Once again I am impressed as ever by Audacity as I now have a working recording station on a computer that would otherwise be on the dungheap.

[steve]

Just a quick update on my current configuration:

Disabled pulseaudio from automatic start up, and set ALSA as the defaults for everything (system sounds still work).

Installed Audacity 1.3.8 alpha.

Set the recording input to "ALSA: default" and the playback device to "ALSA: dmix".

This seems to be the optimum configuration on this (Ubuntu 8.10) computer. I could possibly get better performance using a real time kernel, but the current set-up is sufficient for my needs, and I'm not inclined to update the kernel as the release of "Jaunty" is just round the corner.