Xvid b-frame decoding problem

[Gaia]

I noticed strange decoding problem. I am not sure what is latest Nic decoder(tried few versions) but there are sometimes strange "flashing" white or black horizontal lines. They don't go through whole screen, sometimes they are shorter sometimes bit longer. I tested ffdshow and Divx5 fourcc and couldn't spot them so it must be decoding problem. There's no point to give any specific settings because they are really hard to reproduce. Now then i think i have seen few of those lines in every Xvid b-frame movie i have encoded but now i am trying to encode movie called "The Bunker" and there's lots of them. This can be also hardware problem. Have anyone else noticed this? I can't give screenshot right now because i am in the middle of encoding. I can't be 100% sure but i think this happends only with b-frame movies.

[Rrrough]

sounds a bit like a hardware-prob. you surely ticked divx5-compatibility and disarmed packed bitstream. all my b-frame decoding problems (until now) were related to not using divx5-compatibility resp. trying packed bitstream and of course the famous b-frame + gmc prob.
were u using 11/18 build with qpel and/or gmc ? just some thoughts.

cheers

[Gaia]

It happens with all the builds. It doesn't matter what settings i use. Ffdshow and Divx5 fourcc works fine. In most cases it's just 1 or 2 line in whole movie but the latest movie was full of them. I am having some strange hardware problems but because ffdshow and Divx5 works perfectly... Anyway this is not that big problem.

[Isibaar]

@Gaia:

This is a known issue with b-frame decoding currently. There is some common code between the b-frame (decoding) and the qpel interpolation process. Since I had to change the qpel interpolation code several times recently to match the standard, those changes also affected b-frame decoding (and unfortunately introduced the horizontal lines).

So your problem is for sure not hardware related and it's nothing to worry too much about (hey, it's just a decoding flaw in the dev-api-3 tree after all ;)). I'm planning to rewrite the whole interpolation code anyway soon (but I want to have GMC settled down a bit before), so the bug will be fixed then.
I could also commit a quick fix if it's really important (but since besides you noone noticed yet... ;))

@Rrrough:

I've fixed some "packed bitstream" encoding bug fixes last week as well as added proper packed b-frames decoding support. So it would be quite interesting to know if the "packed bitstream" option still introduces artefacts.
Unfortunately VDub has no special support for XVID bframes yet, so for the time being better set the FOURCC to DX50 in the XVID config dialog if you want b-frame encodings without delays...

[Rrrough]

I've fixed some "packed bitstream" encoding bug fixes last week as well as added proper packed b-frames decoding support. ok, I'll give it a try. thanks for the tip with vdub.
nice to see all you devels here, thank you all for this incredible masterpiece of code ;)

cheers

[Isibaar]

I've commited a fix for the horizontal line problem. I've also added bframes+qpel decoding support as well as some speedups for qpel and bframe decoding in general.

Please report if your problem is fixed now...

[Rrrough]

did a small test clip with uManiacs 11/20 build and can confirm that the packed bitstream is working nicely now. qpel + bframes are giving great results when used together ! decoding works nicely.
thanks again for your work. the only thing missing now would be mpeg/custom quantizers working with b-frames ;).

cheers