asking xvid encoder setting

Hi all,


anybody here have experience converting MJPEG to avi with Xvid?

I have matrox rainbow runner , i use it for capturing tv programmes.
Fyi, the mjpeg quality i choose is medium or better, and the 
resolution always 704x576-50 fields/sec.

Vdub 1.5.10 is the tool, with filters:
- smart deinterlace ,threshold : 10
- resize ,precise bicubic 0.75 : 640x480
- color equalizer (my mjpeg a li'l bit greenish) ,red 0 / green -9 / blue +9

Compression is 2 pass Xvid 1.0.3, default settings, bitrate 1000Kbps

Lately i realize that i got mixed-bag results.
When tv picture quality is crystal clear, the Xvid result is good ,
but many times the bitrate goes up to 3 times i set (in this case upto 3xxx Kbps).
When the picture quality has some noises, Xvid result is rather poor
(blocky, murky) even if I set the bitrate higher, still got poor result (especially
if compared with *cough!*x264*cough!* )
Somehow the codec seems to compress more when it sense the noise,
and the average bitrate reported is around 7xx-8xxkbps.
It's rather confusing, because usually noisy picture affect the codec
to compress lesser than it should, but in not my case.
I tried many settings: trellis, target size, chroma motion, qpel,
adaptive quantization, etc .
Even with version 1.1.0-beta2 , the situation hasn't changed .

Any suggestion, please?

If the dev team would like to have the 'raw mjpeg' (43Mbytes)
for tests, let me know the email address since i only have dialup connection
and will send it part-by-part (.rar) . Thanks.

Regards,
FirmanD