Blocks during high motion scenes

[Shinzon]

Hi,

I tried to encode my Extended Edition of a famous movie(playtime 3h 45m) with GordianKnot and XviD-24062003-1 to a size of 1500MB including two vbr mp3 audio files. The result looks very good but during fast scenes blocks or noise appears. I tried to play the encoded movie with ffdshow and the normal Xvid direct show filter, but the blocks still appear.

My Settings:

codec: XviD-24062003-1
average bitrate: 754kBit/s
resolution: Pal 16:9 720 x 576 resized and cropped to 544 x 224

1 Pass:
quantization: h.263
VHQ: Wide Search
max b-frames: 2
b-frames quantizer ratio: 150
b-frames quantizer offset: 75
b-frames treshhold: 40 (I read this value is good for low bitrate)
chroma motion on
quaterpel on
choma optimizer on

2 Pass:
same settings
quantizer restrictions default

Before encoding I reseted Xvid to default settings!
I did several encodings and changed the b-frame treshhold and the amount of b-frames, but the blocks always appeared.

Please help :)

[EthanoliX]

Some things I tried to avoid blocks esp. during high motion scenes:

- for 2pass 2nd pass try lower values for max. overflow improvement/degradation, but be aware that this might lead to unpredictable filesize

- try mpeg matrix. I know that h.263 is recommended for low bitrates, but even with 1pass @ quant. 2 and default settings, h.263 produces blocking artifacts (Dreamworks trailer, panning through the clouds)

- try newer version of XviD

Hope this helps

[Blue_MiSfit]

definatley try a new version of XviD... RC1 / Beta3 are vastly superior to the old dev-api 3 builds IMHO.

~misfit

[K_R]

Lots of people will say that quant capping is pointless because the RC can handle everything perfectly, but I suggest giving it a go. Say, something like i:2/4, p:2/8, b:2/31. The reason you get blocks in high motion scenes is due to the RC calculating that since it's high motion it can increase the quant because the quality loss will be less perceptible, I think. But if your show is not easily compressed the quant gets pushed up into values where the blocks become painfully visible.

[Shinzon]

I will try your suggestions.
Thanx for your help.

[Kb_cruncher]

You might like to try using my default b-frame settings.

max b-frames: 3
b-frames quantizer ratio: 175
b-frames quantizer offset: 125

I find these to give the best results at low bitrates for me.Having more bframes will allow a better iframe quant, which you get a lot of during high motion scenes.
I too also recommend using the latest XviD RC1 release.
If you decide to give this release a try, i would recommend using Trellis,Adaptive Quantisation and ChromaMotion together as they give very good compression when combined.

You don't mention what resizer you use.Try "BicubicResize(544,224,0.333,0.333)".
This is a soft resize and will help to reduce those artifacts some more.

Of course, you can always increase the bitrate.You will be glad you did in the end;)