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Audio scrubbing problems

stephans
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Audio scrubbing problems

Thu Apr 24, 2014 2:48 pm
Hi everyone,
I use Kdenlive for Audio Dubbing. Although it is not specifically made for this task it works really good. One feature that is essential for me is audio scrubbing. On the first machine I installed it it worked great, but now I set up another machine (a notebook) and there audio scrubbing is not really working. When I scrub/do frame by frame playback, I hear random audio samples here and then but most of the time I hear nothing. What I can say is:

* I use Ubuntu Studio 14.04
* as there are no Ubuntu-Trusty packages in Sunab's repository I used Kdenlive from the distribution
* Audio codec is AAC
* I tried Pulseaudio and alsa for audio playback
* According to top the CPU is at ~50% while scrubbing

Does anybody have an Idea what could cause this problem and where I should look to debug it? What do you think this could most likely be: a Kdenlive/Ubuntu/Soundcard/Whatever issue? Any hints are welcome as I am stuck here.

Thanks! Stephan
User avatar bcooksley
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Re: Audio scrubbing problems

Fri Apr 25, 2014 12:11 am
Are there any differences in software versions, etc which could account for the failure of audio scrubbing to work? If the scrubbing process requires recording audio, you may wish to verify that is working as it is intended to - Pulseaudio has been known to garble this in the past.


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stephans
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Re: Audio scrubbing problems

Mon Apr 28, 2014 10:31 am
Thanks for your reply! At least Kdenlive, MLT, libav and frei0r are only different in ubuntu specific subversions. I did some more testing and definitely got pulseaudio out of the loop without any change of my problem. What do you mean by "If the scrubbing process requires recording audio"?
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Re: Audio scrubbing problems

Tue Apr 29, 2014 10:24 am
I'm not familiar with the audio scrubbing process - hence why I asked if it involved recording audio (which is where Pulseaudio could have interfered).
In any case, removing Pulseaudio hasn't altered the problem...

The Ubuntu specific sub-versions could be important here - could you try making them match if possible? It may be that a distribution specific patch or a patch backported by the packagers is fixing / breaking this.


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stephans
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Re: Audio scrubbing problems  Topic is solved

Sun May 04, 2014 1:22 pm
I think you were right about the ubuntu specific changes. I forced kdenlive back to the last "saucy" version and the scrubbing worked again! My guess is that it was caused by the upgrade to 0.9.6-3 ("Move from ffmpeg to avconv"). Thank you for your help!
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Re: Audio scrubbing problems

Tue May 06, 2014 9:24 am
Thanks for the confirmation - please post an Ubuntu bug about that so they can investigate further and correct the issue.


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