View Full Version : BIG Custom Matrix problem

crOOk
22nd October 2002, 20:31
I'm having trouble using custom matrices. The result usually turns out very blurry, with lots of trails, artifacts etc., just like a very high quantizer would have been used, but the size is 28kB larger than the MPEG quantizer video (Both viedos are constant quantizer 2 - 2Pass, FirstPass). I've appended a short 30 frame clip of the beginning of the seventh chapter of Shrek, PAL DVD. It looks horrible, believe me. This is my AVS script:

LoadPlugin("c:\dvd\MPEG2Dec3b6.dll")
LoadPlugin("c:\dvd\lanczos3.dll")
MPEG2Source("C:\dvd\S\1.d2v",cpu=0,iDCT=1,moderate_h=40,moderate_v=60)
crop(1,4,718,568)
lanczos3Resize(576,320)

I used Nic's DVD2AVI version and his newest (10/21/02) XviD build. The problem appears with older builds, too, though. These are my settings:
Motion Search Precision 6, FourCC is XviD, there is one I-frame (which looks perfectly fine) in the clip, No lumi masking, interlacing or B-frames have been used. In the example clip I set the matrices to CG Animation, but the problem appears with every Custom Matrix, even the official MPEG one. I've been having this problem for a while, but since I want to encode Shrek now, I'm really curious how it will affect the quality/size to use the CG animation matrix when reencoding this clean animated source. Would - Someone - Please - Help - Me?
-h
22nd October 2002, 21:30
Are you using ffdshow to decode the sequence? There were a couple bugs in libavcodec concerning custom matrix quantization.

Try playing the file in VirtualDub - if the same artifacts appear, it's an XviD problem.

-h
-h
22nd October 2002, 21:36
I just tried your attachment, and it worked fine for me. I am using the latest compiled version of ffdshow.

-h
crOOk
23rd October 2002, 04:15
That would be a pretty lame mistake, wouldn't it? Well, however, I'm gonna try it out right now and will post my answer by tomorrow... Thanx for the quick reply!
crOOk
23rd October 2002, 04:41
Downloaded dev build 10/14, was using build 9/20 before. It works fine now. Don't know why I didn't think about looking at the frames... Thank you -h!
MrBunny
8th November 2002, 13:27
Hi, I'm sorry for reviving an old thread.
I ran into this problem as well, and it seemed to be resolved using Nic's dshow decoder. However, I was hoping that someone could confirm for me that custom matrices are completely MPEG-4 compliant (and if there are any min/max values accepted by the standard). AFIAK, ffdshow is a "generic" MPEG-4 decoder, and thus problems with custom matrix playback seems to worry me in this regard. Especially with all the issues surrounding Qpel, ffdshow and the MPEG-4 standard, I prefer to be on the safe side.

TIA

Mr. B
-h
8th November 2002, 18:05
XviD's custom matrix support appears to completely match the standard, and works with standards-compliant decoders. I don't have access to the spec right now, so I can't check if there are any min/max values specified. You may have to use trial and error checks.

-h