Sluggish video preview with mlt 0.7.0

[Richard]

1. Fedora 14 x86_64
2. RPM (RPMFusion)
3. Openshot 1.3.0

I'm the Openshot maintainer for Fedora. I got a but report against mlt in RPMfusion that the upgrade to 0.7.0 made playback sluggish. For him, 1 frame every 10 seconds. A quick test on my system with AVCHD video showed stuttering but still watchable video.

Downgrading to mlt 0.6.2 seemed to help.

Is 0.7.0 supported or is it too new? Kdenlive doesn't appear to be affected.

[Andy Finch (fincha)]

The best way to test it is to use the melt command line player to playback the videos (this is independent of Openshot or Kdenlive).

[Richard (hobbes1069)]

Ok, I got a response from the user. You can see the full details here:

https://bugzilla.rpmfusion.org/show_bug.cgi?id=1688#c19

But to summarize. He's got 1080HD video with PCM audio, Ogg music track, transparent PNG's on top.

It seems the first clip plays slow but OK and goes south after the first transition.

I assume the command line player will just play a video, right?

[Olivier Girard (eolinwen)]

MLt 0.70 seems bring a lot of problem and I have some users who have backported to the official release for re-finding a normal system, see here the comments of Nicolas : https://answers.launchpad.net/openshot/+question/147390 .

[Richard (hobbes1069)]

I took German in high school, not French so I'm glad Google does a pretty good job of translating. :)

It seems the answer is to stick wit 0.6.2.

[GMaq (info-bandshed)]

Hi.

I can confirm this bug exists in Debian (AV Linux) as well, following an update to Kdenlive 0.8 Openshot preview in a project with 1080 HD AVC files is broken showing only a single frame for every few seconds. I see a 7.2 version of MLT is in the works, is the MLT developer aware of the Openshot issues and is the 7.2 version likely to contain a fix ? Unfortunately going back to 0.6.2 is not really an option for my circumstances.

Glen MacArthur - AV Linux Maintainer

[Richard (hobbes1069)]

I'm not sure if upstream MLT are aware of the problem or not... I've pulled the 0.7.2 source and I'm building it now but I will not be able to test it until I get home from work.

[Richard (hobbes1069)]

I have test packages of mlt-0.7.2 available for Fedora

https://docs.google.com/leaf?id=0B4A6of0Rl4nUNWJjNzdhZGEtNmUwMC00ZTk4LThjNDYtYjcyNGQ0ZmYxYzBh&hl=en

[Richard (hobbes1069)]

User report states that 0.7.2 is no better than 0.7.0 for video preview.

https://bugzilla.rpmfusion.org/show_bug.cgi?id=1688#c25

[Jonathan Thomas (jonoomph)]

I have not personally tested OpenShot with MLT 0.7.+ yet, as I've been working on a new project which is taking much of my time. However, I'll give this a test tonight, and contact upstream MLT if needed. Thanks!

[GMaq (info-bandshed)]

@Richard

Thanks for sharing that info, 0.7.2 predictably is still problematic here on Debian as well unfortunately.

Hi Jonathan,

Thanks for looking into it, I realize this is not a convenient time for this issue to pop up when you are already busy and have a new release just about ready, such is the life of a Linux developer it seems...

Hopefully it isn't too major to fix, We'll look forward to what you find out.

[Jonathan Thomas (jonoomph)]

I did some testing with the newest version of MLT (0.7.2) and the latest GIT version, and I don't see any problems with my test videos. The 0.7 series of MLT introduced some multi-threading (i.e. pthreads), and I wonder if that might be slowing down computers with only 1 or 2 cores. My computer has 4 cores, and AVCHD seems about the same as it's always been. In other words, AVCHD is a bit choppy, but still usable and watchable.

It might be helpful to attach a "small" AVCHD video clip to this bug report, and other users can test for choppiness. It might have something to do with the resolution, bit rate, codec, or some other factor. However, at this point, I can not reproduce the problem, and so I don't feel like it will be helpful to contact the MLT developers at this point. If we can learn a bit more, that will help us make a case. =)

[Richard (hobbes1069)]

Here's the response from my user:

https://bugzilla.rpmfusion.org/show_bug.cgi?id=1688#c27

It looks like he's using a quad core machine, the main problem seems to be transitioning between videos.

[GMaq (info-bandshed)]

Hi,

I am seeing this issue on a Quad core as well, the interesting thing is if I import a single clip into Openshot and play it back it works, however opening an existing project with many joined short clips from the same source files results in the playback issues, it is so pronounced than on many of the short clips only a single frame is displayed in the preview window.

For what it's worth the files are 1920x1080 .mov files with AVC Video and PCM Audio from a Canon Digital Camera. I'm uploading one for the sake of testing here (May not be finished uploading until a while after I post this):

http://bandshed.net/files/MVI_2503.MOV

[Jonathan Thomas (jonoomph)]

I have been able to reproduce the error, or mostly reproduce the case where the stuttering seems completely unusable after using the same clip a few times and seeking around a bit. So, I have reported the problem upstream to the MLT developers, and I'll keep everyone posted on this bug report. Thanks!

[Jonathan Thomas (jonoomph)]

Dan Dennedy (MLT maintainer) has found the problem, and it is due to a de-interlacing bug which apparently is slowing down preview pipeline. He expects to check-in a fix this week-end, and I'm not sure when the next version of MLT will be released, but hopefully sooner than later. I'll post another update once I see the fix checked in. Thanks!

[Richard (hobbes1069)]

Good to know! Thanks!

[Jonathan Thomas (jonoomph)]

I have just tested a patch (from Dan) to MLT that fixes (for me at least) all the performance issues (i.e. stuttering and freezing) in the 0.7+ series. Dan has not committed it yet, but I expect it will make it into the source code soon. Probably the next release of MLT will include it.

[GMaq (info-bandshed)]

Hi,

Thanks very much Jonathan (and Dan) for getting this fixed.

I can confirm that the patch has been committed to MLT GIT and an MLT build tonight (20110509) from GIT solves the issue here as well. Seeking is much smoother and the preview no longer has stuck frames. I still see a slight pause when moving from one clip to the next but I'm guessing that issue differs from the original problem/symptom and therefore was not addressed by this patch.

 It is always amazing to see this level of co-operation between developers.

Thanks again!

[Richard (hobbes1069)]

Awesome! I may try doing a GIT build but I would rather wait for an official release if it will happen relatively soon.

[Andy Finch (fincha)]

MLT have released a new official version, 0.7.4 that includes this fix.