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IDProjectCategoryView StatusDate SubmittedLast Update
0000568KdenliveMLTpublic2009-01-05 14:202009-11-15 23:33
Assigned To 
Platform64 bitOSDebian LinuxOS Version4.0
Product VersionRecent git 
Target VersionFixed in Version 
Summary0000568: Sound stutering
DescriptionI have three computers installed with Kdenlive. During the week-end, I took the laptop and was surprised that sound was stutering playing simple Mpeg2 HDV files. It seems like a problem of low latency of the ALSA driver.

I can only reproduce this problem on my laptop.

Would it be possible to set the latency of the ALSA audio driver (if this is the explanation)?
TagsNo tags attached.
Build/Install MethodManual build from SVN
Attached Files

- Relationships
has duplicate 0001221new Persistent Audio distortion during preview after stuttering 

-  Notes
ddennedy (developer)
2009-01-05 21:13

We just SDL and there is very little control through the API. I doubt it is the latency, but you could try the DSP option to use OSS and see if it is different. Also, make sure that your default ALSA PCM is not routed through PulseAudio.

Finally, not too long ago HD MPEG-2 decoding was an issue and really required XvMC, hardware-assisted decoding for full performance.

Please change the category to MLT, and I will take assignment because MLT does need some improvement to prevent sound stuttering when decoding is not fast enough. It tries, but it is still not good enough. Also, change the priority to low. Thanks.
jmpoure (developer)
2009-01-06 13:26

Done. Maybe this can be addressed together with H.264 decoding too? Maybe a solution would be decoding only I frames? Bye.
repli2dev (reporter)
2009-01-06 15:47

I have exactly same problem. Problem is appearing in any kind of video and audio files if I do overflow my CPU for a few moments, but after it stutering stay (without reason - CPU is back to normal).
ddennedy (developer)
2009-01-06 22:29

> Maybe a solution would be decoding only I frames?

Yes, the thought has occurred to me previously.
madsdyd (administrator)
2009-01-10 23:49

Acknowledged by ddennedy.
jmpoure (developer)
2009-04-05 10:54
edited on: 2009-04-05 10:58

I was not able to test OSS as I don't have OSS running in recent kernels.

Same problem reading a long Audio file.

IMHO, this could be a latency problem using Alsa driver. My computers are all dual core and problems only arize on certain audio cards. Therefore I think this is a latency problem. Sometimes the default latency is too short.

Users should be able to set a default latency in Kdenlive/MLT, whenever possible.

What you mean is that latency problems arise in the SDL portion of MLT, before it is being routed to Alsa or whatever sound system.

Kind regards,

raps (reporter)
2009-10-24 23:38

I have the same problem on Xubuntu 9.04.
Using standard configuration (ALSA driver ?) I had no sound problems (but annoying crashes when playing a video and after that selecting a clip in the tree view).
After re-installing pulseaudio I have no crashes any more but a cracking sound.

The clips are coded in DVD PAL 16:9 format, container avi.
VLC is playing the clips without problem.
CPU usage goes high when playing the video in the timeline or with VLC, as my computer has a weak configuration (CPU intel celeron M processor up to 1.5 GHz).

Until now I never managed to get Kdenlive not crashing and playing sound when I uninstall pulseaudio... I would be a good test.
raps (reporter)
2009-11-15 23:33
edited on: 2009-11-15 23:34

I could reduce the stuttering problem on my system this weekend.
I followed the instruction of this page: [^]

Q. PulseAudio is working correctly, but I am noticing some stuttering on my system. Is there anything I can do to help?
A. Edit the file /etc/pulse/daemon.conf:
sudo mousepad /etc/pulse/daemon.conf

Find the following lines (usually at the bottom):
default-fragments = 8
default-fragment-size-msec = 10

I use 20 and 2 for my sound card.
I only have a light cracking noise when the sound level gets high (when a sound volume in the video gets high). I would say that 95% of the problem is solved for me.
Hope this helps.
Note: to restart pulseaudio simply use "pulseaudio -k", it kills the process.

- Issue History
Date Modified Username Field Change
2009-01-05 14:20 jmpoure New Issue
2009-01-05 14:20 jmpoure Build/Install Method => Manual build from SVN
2009-01-05 21:13 ddennedy Note Added: 0002075
2009-01-06 13:25 jmpoure Priority normal => low
2009-01-06 13:25 jmpoure Category User Interface => MLT
2009-01-06 13:26 jmpoure Note Added: 0002080
2009-01-06 15:47 repli2dev Note Added: 0002082
2009-01-06 22:29 ddennedy Note Added: 0002086
2009-01-10 23:49 madsdyd Note Added: 0002099
2009-01-10 23:49 madsdyd Status new => acknowledged
2009-01-15 08:43 jmpoure Note Added: 0002151
2009-01-15 08:43 jmpoure Note Deleted: 0002151
2009-04-05 10:54 jmpoure Note Added: 0002639
2009-04-05 10:54 jmpoure Note Edited: 0002639
2009-04-05 10:58 jmpoure Note Edited: 0002639
2009-10-24 23:38 raps Note Added: 0004206
2009-10-27 03:47 ddennedy Relationship added has duplicate 0001221
2009-11-15 23:33 raps Note Added: 0004282
2009-11-15 23:34 raps Note Edited: 0004282 View Revisions

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