White video output on some mpeg files

[Andy Finch]

Some mpeg files display a white screen after they have been cut with the razor tool. This issue was originally reported on the forum as white output when the video is muted, however I have found that just cutting a clip is enough to display the white output.

http://openshotusers.com/forum/viewtopic.php?f=11&t=121

Steps to reproduce:

1. Drop the attached mpeg file on to the time line.
2. Cut the file into 3 roughly equal portions.
3. Set to play - when the playhead reaches the 2nd clip the video output is white.

The only other mpeg file I had (from a different source) wasn't affected by this, but it was only 11 seconds long, so not sure if it is related to length or some other property of the file.

Reproduced on bzr version 181, Jaunty 32 bit, MLT version 0.4.4 (from TJ's old repository).

[Olivier Girard (eolinwen)]

Today, i have reproduced it on a MPG file with the same steps.
I have cutted it in three parts. When i preview the file, i'm reading the first part but at the second and after the third i have a white ouput, each time that i want to see it.
I'm testing on the bzr version 181, Karmic 64 bit, MLT 0.44 (official version) AMD 4850 graphic card with Compiz actived.
NB just bevore cut the file in three parts , i have none problem when i was previewing.
It's perhaps because we have done a cut not a key frame (just a throught) . You know the images I (B and J are not essentials about the informations that they contain, if i well remember on a Gopfile (mpeg,mpg)). In fact, our cut is not precised and it missed some informations in the file and it's why we can't read it.

[Andy Finch (fincha)]

Yes that could well be it regarding the I frames.

2010/1/5 cenwen <email address hidden>

> Today, i have reproduced it on a MPG file with the same steps.
> I have cutted it in three parts. When i preview the file, i'm reading the
> first part but at the second and after the third i have a white ouput, each
> time that i want to see it.
> I'm testing on the bzr version 181, Karmic 64 bit, MLT 0.44 (official
> version) AMD 4850 graphic card with Compiz actived.
> NB just bevore cut the file in three parts , i have none problem when i was
> previewing.
> It's perhaps because we have done a cut not a key frame (just a throught) .
> You know the images I (B and J are not essentials about the informations
> that they contain, if i well remember on a Gopfile (mpeg,mpg)). In fact,
> our cut is not precised and it missed some informations in the file and it's
> why we can't read it.
>
> --
> White video output on some mpeg files
> https://bugs.launchpad.net/bugs/503112
> You received this bug notification because you are a direct subscriber
> of the bug.
>

[Bob Heide (rheide)]

I reported this problem originally in the forum.

I'm using Karmic 32 bit, MLT 0.4.4-2build1 and Mobile Intel Graphics Media Accelerator X3100 with Compiz active.

[Dan Forster (sm0ked0g)]

I am also having this problem on Ubuntu 10.4 Release Candidate using Openshot 1.1.3 with an mpg file.

[Giorgio M. (motolo79)]

i have the same problem on ubuntu 10.04.

[Guraknugen (guraknugen)]

Same problem, Ubuntu 10.04 and the 1.1.3 version of OpenShot from the repositories. MLT? Don't know what that is, sorry.

The problem occurs for me on all mpg clips I tried so far. If I split a clip the first part of the clip is unaffected, so it seems like it needs the very first frame of the clip to be able to produce pictures. I have also tried to trim clips. When I trim the end of a clip nothing bad happens. The white frame thing only happens when I trim the beginning of a clip, however at least once I tried it, it actually worked as it should with no white frames.

I can include a short mpg file here if you want, but I noticed someone else already did, so I'll wait for a request instead.

[Matias Fernandez (matiasfernandez-hda)]

I have the same problem since I use 10.04, sorry that has not yet been able to solve, there is no better program to edit video on Linux.

[Lukáš Neoproud (neoproudek)]

It affects my videos, too. Please solve this problem.

[Andy Finch (fincha)]

I spent some time looking at this bug tonight. I haven't been able to fix it, but did notice a couple of things which might be pointers to the problem.

Cutting the same video in Kdenlive does not result in white output. Comparing the xml files between Kdenlive & Openshot, there is a difference of 2 frames in the in & out points & overall length of the clip (the length in frames is reported as 1705 in melt, 1707 in Openshot). This may or may not be relevant.

While working with the clip, the line:

[mpeg1video @ 0xaf0a5640]Missing picture start code

was output occasionally, which may indicate that we are cutting in a segment that doesn't contain an I Frame - I'm not sure under what conditions ffmpeg throws out that error. Mpeg video contains I frames (key frames), P frames (predicted frames) & B frames (bi-directional predicted frames), it is not possible to playback a segment of video before the first I frame in the segment, so if we are cutting out the I frame, this would explain the white output.

I'm not sure how we can ensure the cut segment includes an I frame, or even if that is desirable, as that would result in the cut being a number of frames away from where it was intended to be (there are usually 12-15 reference frames per I frame).

More research required.

[Olivier Girard (eolinwen)]

| t is not possible to playback a segment of video
before the first I frame in the segment, so if we are cutting out the I
frame, this would explain the white output.

I'm thinking the same thing : good analyze. And i said more : that could explain the problem with the output video and output audio that some people was having met. And certainly the same thing for the ogg format because the I frame contain some informations that not having the others because it is a duplication partial or total of the I frames.

[Dan Dennedy (dan-dennedy)]

Does "MPEG" mean MPEG-1, MPEG-2, MPEG-4p2, MPEG-4 AVC, or all of the above?

I see one comment that indicates "mpeg1video." FFmpeg has known problems with seeking on some MPEG-1 video files. Sometimes the problem goes away after recoding them with ffmpeg:

ffmpeg -i original.mpg -sameq -acodec copy -vcodec mpeg1video %1.mpg

[Dan Forster (sm0ked0g)]

In my case it is a "MPEG-1 Layer 2" file, according to GSpot (windows app).

I will try what you suggested and see if it works for me, thanks for the tip.

[Dstl (dstilio)]

My case:

the videoclips I use were created through Openshot (from a MTS video of my camera) with the profile:
Vimeo HD --> 720p 25 frames --> high quality (I think it generates mp4 x264 files?)

I have this problem in a very intense way when I use any one of these videoclips and try to generate a new video clip by going to the "speed" tab and make the video play backwards (reverse).

Then at the beginning of the new exported video I get black and white frames.
So it is from Vimeo HD to Vimeo HD export.

[Olivier Girard (eolinwen)]

What is your version of MLT ?
If you are using the 0.5.6 you should update it with those (0.5.10) is in the sunab repository.

[Dstl (dstilio)]

cenwen,

I have the 0.5.10 from sunab. Still this bug is there.
As I said, I mainly see this issue in the reversed video clips. not sure if this bug always appear if not in reversed video clips.
I have to check.

[Olivier Girard (eolinwen)]

Hi Dstl,
Did this bug is always present with the last version of MLT (at least the 0.6.0 or greater ) ?
Thanks.

[Dstl (dstilio)]

Hi cenwen,
the problem is still here with the following configuration:
Ubuntu Lucid 10.04
frei0r-plugins: 1.1.22git20090409+repack-0ubuntu3
libmlt++3,
libmlt-data,
libmlt3,
melt,
python-mlt3 --> all of them are now at 0.6.2-2~ppa1~lucid1 version
Openshot: 1.3.0-1nf1~ppa1~lucid1

[Olivier Girard (eolinwen)]

Hi Dstl,
Did this bug is always present with the last version of MLT (at least the
0.72) ?
To have the last version of MLT (
http://openshotusers.com/forum/viewtopic.php?f=12&t=758)
Thanks.

2011/2/27 Dstl <email address hidden>

> Hi cenwen,
> the problem is still here with the following configuration:
> Ubuntu Lucid 10.04
> frei0r-plugins: 1.1.22git20090409+repack-0ubuntu3
> libmlt++3,
> libmlt-data,
> libmlt3,
> melt,
> python-mlt3 --> all of them are now at 0.6.2-2~ppa1~lucid1 version
> Openshot: 1.3.0-1nf1~ppa1~lucid1
>
> --
> You received this bug notification because you are a member of OpenShot
> Developers, which is subscribed to OpenShot Video Editor.
> https://bugs.launchpad.net/bugs/503112
>
> Title:
> White video output on some mpeg files
>
> Status in OpenShot Video Editor:
> Confirmed
>
> Bug description:
> Some mpeg files display a white screen after they have been cut with
> the razor tool. This issue was originally reported on the forum as
> white output when the video is muted, however I have found that just
> cutting a clip is enough to display the white output.
>
> http://openshotusers.com/forum/viewtopic.php?f=11&t=121
>
> Steps to reproduce:
>
> 1. Drop the attached mpeg file on to the time line.
> 2. Cut the file into 3 roughly equal portions.
> 3. Set to play - when the playhead reaches the 2nd clip the video output
> is white.
>
> The only other mpeg file I had (from a different source) wasn't
> affected by this, but it was only 11 seconds long, so not sure if it
> is related to length or some other property of the file.
>
> Reproduced on bzr version 181, Jaunty 32 bit, MLT version 0.4.4 (from
> TJ's old repository).
>
> _______________________________________________
> Mailing list: https://launchpad.net/~openshot.developers
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> Unsubscribe : https://launchpad.net/~openshot.developers
> More help : https://help.launchpad.net/ListHelp
>

--
Olivier
Cenwen un elfe sur la banquise/ an elve on the ice
Mon blog perso sur le multimédia, Ubuntu, Linux et OpenShot :
http://linuxevolution.wordpress.com/
Le forum d'Openshot où vous me trouverez : http://openshotusers.com/
http://openshotusers.com/forum/index.php

[Andy Finch (fincha)]

This seems fixed now when using MLT v0.7.6