ffmpeg/ffdshow h.264 cabac decoding buggy

[bond]

i recently did some tests with the h.264 decoder from ffmpeg (as used in ffdshow) and it seems that there is a bug somewhere as i got "jumping", "flickering" artifacts sometimes in some blocks

i tried different settings (with or without multiple reference frames/cabac/lopp filtering...) and it seems its handling of cabac is causing the artifacts

can anyone confirm this?

[stephanV]

in the latest ffdshow, H.264 is marked as "incomplete", so wheter this is a bug or not i don't know. i wouldn't use that part of the ffdshow-decoder yet though.

[bond]

Originally posted by stephanV
i wouldn't use that part of the ffdshow-decoder yet thoughwell incomplete can also mean that the decoder is simply not complete ;)
meaning it doesnt support decoding all tools offered in h.264 (as the mpeg-4 asp decoders also needed some time to be able to decode advanced tools like qpel, gmc aso...)

still it seems that ffmpeg already supports decoding multiple reference frames, variable block sizes, loop filter and cabac/cavlc, but cabac seems to be buggy (i started this thread to ask whether someone can confirm this)

[Nic]

Yup, cabac is buggy in decoding, seems buggy in the moonlight one too really (along with b-frames). Was working with the reference software last night, added AVS support (I know it's been done before, but couldn't find their code). Interesting stuff, got encoding to bareable speeds, encoded the new Aliens vs Predator trailer (with sound) with it, I'll upload it later for those interested...

-Nic

[bond]

thanks for confirming this, nic :)

btw if you have time maybe it would be nice if you could have a look at this issue in ffmpeg too :D
i think its very important to also have a good opensource decoder and not only commercial ones (which limit the usage a lot: only want to connect to their filters, only support specific 4ccs aso..)

cant wait to play with your h.264 goodies :)

[Nic]

I had to upload something for dragongodz so I uploaded the demo I did. Not very impressive, but seeing it was done with constant quant of 25, it shows what could be done with good ratecontrol (the bitrate control is pretty useless in the reference encoder if turned and doesn't makes good decisions ;) )

http://nic.dnsalias.com/avp.avi
(Alien vs Predator trailer, play with ffdshow for best results 4.15mb)

-Nic

[bond]

what settings did you use to encode the stream, nic?

[Nic]

Can't actually remember, and i've changed it now...remember the QP was set to 25 though...no cabac. That's all I can remember :(

[bond]

ok, just wanted to know cause i can decode it in realtime on my old pentium3 866mhz :D

[Sharktooth]

Where can i find the AVP trailer?

[Nic]

What? Do you mean the original?. The original was a sorrenson mov file off the apple website. My converted version is at the link in my post above.
i.e. http://nic.dnsalias.com/avp.avi

-Nic

[Sharktooth]

I mean the original. the one on the apple site is ... ehm... different... maybe they "updated" it :)

EDIT: Now there's a preview and a trailer...

[Nic]

Cheers for the info. Downloading it now :)
edit: downloaded. That's the one they are showing in cinemas round here at present...

[Sharktooth]

Too bad in italy AvP will come on 12/11/2004...
I'm still looking for good HD trailers.

[malkion]

@ Nic

For a QP25 encode, that h264 video looks very good.

However, that doesnt mean Quant 25 does it?

[Nic]

It does mean Quant 25, kinda ;) But H264 has quants from 1-51 unlike MPEG normally which is 1-31. So 25 isn't that bad.

[bond]

so when will we see you h.264 code, nic? ;)

[Nic]

LoL...Just been hacking around with it. Will do more. Did people have problems with the VFW interface? Works so well for me. I remember people mentioning that in VDub it says it only supports 24bit and 32bit input (but that only refers to RGB not YUV so it shouldn't cause any problems)...

Apparently when it comes to writing rate control code, I suck ;) lol My CBR exploits were a bit poor (kinda worked, but not accurate enough). So I'll go for two pass code, might see if Koepi is free to help me there... :)

I'll try profiling x264 to make it faster too, profiling and making the reference source code is easy, x264 is more tricky as it's already been optimised (so I don't have many clues on making it faster).

Can't wait for Skal's code to come out...Everything he does has genius written on it, so should be good :)

Just playing around,
-Nic

[pogo stick]

Is XviD project started that way? :)
By joining more and more people?
Somehow I have a good feeling about future of x264. :)

[Koepi]

Uh, uh, 2pass coding, let's talk on IRC, you know where :-) I'd like to code something that i'm capable of ;) (what about QuEnc 2pass code?...)

Regards
Koepi

[d'Oursse]

Nic: according to skal, it's not sure that he will release the source of his h264 codec. A company was interested in it. But nothing is sure (i asked him some days ago, when he was on #xvid). And yes, he is a quite impressive man, indeed :)

[Nic]

:( That's a shame, i'm sure it would be impressive. We'll I wish him the best of luck with it :)

edit: Maybe he could release it as GPL, but just license the sourcecode for commercial use. Like MySQL does it :) Hey I can dream... ;)

[CruNcher]

d'Oursse he said he only would if its Open Sourced :d

[d'Oursse]

Cruncher: you're sure ? i don't remember. If it's the case, it's cool :)

[bond]

i think this cabac with inter 8x8 problem has been fixed today, at least michael niedermayer closed my bug report on sourceforge

can anyone confirm this?