Pauses with B-frames

[sam_b]

I apologise if this has been noted before but..

I have recently tried encoding a clip (futurama fom DVB) which has a scrolling scene at the very start and then stays fairly static for a few frames. It appears that when using b-frames there is a pause just after the scrolling part of the scene the same as the maximum consecutive b-frame interval. There is also some corruption of the surrounding part of the picture during the pause. I would be greatful if someone could confirm this problem or if it's just my system.

If the attatchment is worth approving, it contains an stable-build encoded clip which can be properly decoded by xvid (but not ffdshow alpha... take note) so you can re-encode it to test. I have no idea why ffdshow fails on it. When re-encoded with b-frames it goes wrong with any decoder for me. I used a custom matrix for everything, in case it should matter.

Oh, I tried a couple of alpha builds, and it happened with both.

P.S. please rename attatchment to .ogm, as .ogm is not a valid attatchment type it seems.

[Aktan]

I'm not sure but I think b-frames are still not stable... The 'stable' build that you got, was it from uManiac? If it was, his 'stable' build were not stable for a couple of days, but it should be stable again, (aka no new features enabled)

[sam_b]

It was koepi's 04102002

[bond]

Originally posted by sam_b
It was koepi's 04102002 b-frames arent enabled in this build :rolleyes:

[sam_b]

@bond: Please take the time to read my post properly. The stable build was used only to be used as a working source clip to allow other people to make tests of their own. I used it BECAUSE it does not contain B-frames. The fact that ffdshow fails on this (stable) source clip is just a warning if people try to watch it.

Me providing a faulty clip does not help much as you do not have the original. I am providing the means to test the bug.

This is why I say:
If the attatchment is worth approving, it contains an stable-build encoded clip which can be **properly decoded** by xvid (but not ffdshow alpha... take note) so you can **re-encode it to test**. I have no idea why ffdshow fails on it. When re-encoded with b-frames it goes wrong with any decoder for me.

I could have provided the original MPEG2 stream but this saves on bandwidth and works just as well, as quality does not matter.

[frodoontop]

@sam_b:
I have noticed the same problem with bframes. First I thought I was imagining things, but your clip proves that the problem is with xvid and not with my eyes.

I encoded your clip with Koepi's 17-02-2003 and the problem was there indeed. I just loaded the clip into VirtualDubMod, fast recompress and this is the result:
testclip with bframes.avi (http://members.lycos.nl/xvid/testclip with bframes.avi)
As you can clearly see, there are some skipped frames somehow. While the source file didn't have such problem.

This seams really a bug in current bframes, which need some attention of the developers.

Greetings,
Frodo

P.S.:Forgot to tell you my Xvid settings:
Bframes 3-100-200, Qqpel, Chroma Motion, GMC, no Lumi, no VHQ

[frodoontop]

Can nobody confirm this problem? The problem shows itself in VirtualDubmod very clearly. While in the source there are no duplicate frames, there seems to be some in the file with bframes. You'll find that frames 23 and 24 are the same as well as frame 26, 27 and 28.
By the way I already tested the clip with bframes without gmc. Doesn't matter, problem is definitely b-frames.
To have the source in .avi format, find it here:
testclip without bframes (http://members.lycos.nl/xvid/testclip without bframes.avi)
Hoping for some responses now.....

Greetings,
Frodo

[echo]

I got some dropped b-frames during an x-files episode encode. There was a skipped frame in four cases where there was a fast fade from one scene to another. The middle frame was always dropped. The problem appeared in all latest builds. Admittledly my settings were a bit extreme (5/150/200), but when I tried the 09122002 build by koepi, there were no dropped frames at all. In all cases I was using only b-frames and no other new features at all. So my guess is that something that changed in xvid's code since 09-12-2002 produces this.

Regards

echo

[Morbo]

Its because of Futurama,I gave up on tape and got a dazzle....:D