Nic's DSF postprocessing bug

[Rober2D2]

Version used to encode:

XviD BUILD (Koepi 17.02.2003 18:17:50)
Mode: 2 Pass - (1st pass + 2nd pass int.)
Discard 1st Pass: OFF
Motion Search Precision: 6 - Ultra
Quantization Type: h.263 + New Modulated HQ
FourCC Used: XVID
Max I-frame Interval: 300, Min I-frame Interval: 10
Lumimasking: OFF
Interlacing: OFF
Greyscale: OFF
Max B-frames: 4
B-frames Quantizer Ratio: 150%
Packed Bitstream: OFF
DX50 B-VOP Compatibility: ON
Print debug info on each frame: OFF
Min I-frame Quantizer: 2, Max I-frame Quantizer: 6
Min P-frame Quantizer: 2, Max P-frame Quantizer: 16

Decoder used: Nic's DSF 30/03/2003
Player: BSPlayer 0.86 build 494
OS: Windows 2k Professional.
APP used to encode: Virtualdubmod 0.1

PROBLEM SUMMARY:
I have problem when I try to playback some films encoded with old Koepi's versions. The screen goes completely black if I check any off the Nic's postprocessing options before beginning playback. The problem seems to be caused because of a bug in some old Koepi builds. They added a few frames at the beginning of the film that virtualdub detects as [D] type (Normally the four frames after the first keyframe).

There is no problem if I use ffdshow or I turn on postprocessing in NIC's DSF when the film is already playing. To test about this problem I cut a few frames from the beginning of a film that has this problem, and a few from the middle (Direct stream copy). Obviously only the segment from the beggining had the same problem, so it seems clear that it is caused by the pad [D] frames.

I put a sample from the begining of the film where is the problem in this address:Here (http://us.f1.yahoofs.com/users/b5ed438e/bc/Clips/Beginning+of+the+film.ogm?bc4bwr.AM0lwaMKs)

PD: Don't forget to switch on any postprocessing feature before beginning playback (Deblock, dering or brightness)

[Nic]

Someone's been reading the "how to post bugs" sticky :)
Thanks for the full report, ill look into that soon :)

Cheers,
-Nic

[mf]

Originally posted by Rober2D2
Quantization Type: h.263 + New Modulated HQ
Max B-frames: 4
Modulated quant and B-Frames together are not allowed.

[N_F]

Originally posted by mf
Modulated quant and B-Frames together are not allowed.

This is just the kind of info that needs to be in some sticky and/or FAQ somewhere :)

[Nic]

I must admit that off the top of my head, I dont know why there not allowed without searching. I think perhaps with the upcoming 1.0 maybe we should all gang together and come up with a concise guide/html/faq of all the things you need to know about xvid.

Mmmm. Just searched:
http://forum.doom9.org/showthread.php?s=&postid=261135&highlight=modulated+bframe#post261135
(Koepi's post)

Yup ill add that to the FAQ then, cheers for the reminder mf :)

-Nic

[kilg0r3]

@Rober2D2

Although I can say nothing about the problem, I just wanted to thank you for taking the time to write a good posting. Keep up the good manners! :)

[Rober2D2]

Modulated quant and B-Frames together are not allowed.

Thanks mf. I already knew it is not recommended, but I am not unhappy at all with the results so I think I will continue using it.



Although I can say nothing about the problem, I just wanted to thank you for taking the time to write a good posting. Keep up the good manners!

Someone's been reading the "how to post bugs" sticky
Thanks for the full report, ill look into that soon

Cheers,
-Nic

May be because I am developer too :) and I know what is a vague report from a user. Sorry, no idea about video compression :p

[mf]

Originally posted by Rober2D2
Thanks mf. I already knew it is not recommended, but I am not unhappy at all with the results so I think I will continue using it.
[..]
and I know what is a vague report from a user.
And you don't know the headaches from non-compliant MPEG4 files? Please do not create them. Thank you. Also, modulated + B-frames aren't just out of spec, they are also buggy. That is why.

[snowbeach]

Doom9 used B-frames with MPEG quant type in his last codec comparison. Is his output MPEG4 compliant or not?

Which settings are not MPEG4 compliant in XviD?

[Wuntvor]

MPEG is of course valid, its modulated that is not mpeg4 compliant.

If i recall B-frames works with modulated , but not the way you expect them to :-)
The reason is that modulated changes quantization between mpeg and h263 in a header of some sort, that isnt available in the bframes, so it isnt "modulated" as often as it should.
Ok, I dont swear that this is 100% accurate , but I am sure that the problem is somewhere along these lines..

regards
/wuntvor

[crusty]

If so, wouldn't it be possible to somehow put that header into the b-frame? Or is that so incredibly out-of-spec that it would break everything?

[Nic]

Lets just face it, modulated is not in the spec, so use at your own peril. :)

modulated quant should be the only non-spec compliant thing right now. (I think, but I might be forgetting something...its been a long day ;) )

Cheers,
-Nic

[Assault]

@ crusty

It doesn't matter if that's possible or not because I think the developers won't try to make that work. Why? Well, as already mentioned, modulated quantization isn't mpeg4 compliant and that's one of the most important aims of XviD.

Regards
Assault

[mf]

Originally posted by crusty
If so, wouldn't it be possible to somehow put that header into the b-frame? Or is that so incredibly out-of-spec that it would break everything?
It would probably be possible but as modulated itself is actually already out of spec it'll only encourage more people to use it. And by the time of dev-api-4 (I have an impaired vfw build of it) you won't be able to use it anymore anyway.

[crusty]

@assault & mf:

Ok I understand.
But say the developers invent all sorts of neat tricks and features that would make xvid far better either in quality or compression than any mpeg4-compliant codec, wouldn't it be useful to implement this in xvid as some form of superset of mpeg4. After all, compatability and compliance is only usefull if you need it.
I mean, I for one don't use Divx to watch xvid and I think many others either use ffdshow or xvid as well. And since many hardware devices that are supposed to be able to run divx, like dvd-players and sorts, are built with upgradeable firmware.
There is also a trend now to using PC's much more as media players, especially with the popularity of barebone systems and microatx systems.
I wouldn't mind if xvid would not be mpeg4-compliant if it would be far better than mpeg4 could ever be.
Just some thoughts...

[Assault]

@ crusty

If the developers break mpeg4 compliance it wouldn't be XviD anymore. ;) But I know what you mean. Look into that thread where mf mentions Kludge. http://forum.doom9.org/showthread.php?s=&threadid=51634&perpage=20&pagenumber=2 I think that's exact that what you want. :)

Regards
Assault