DivX5.1 3-pass compared to 2-pass

[DarkWave]

Hi,

there´s just a little question from me. I compared a 2-pass encoding with DivX5.1 to a 3-pass encoding.
And what should i say? Quality is nearly the same except of one huge problem: there are lots more macroblocks in the 3-pass than in the 2-pass.

My settings
2-pass:
GKnot, lanczos, Resolution: 640x352 Pal, Filmlenght: 0:42:25, File Size: 350MB (to get 2 files on one CD), Bitrate: 925KBit/s, 1st/2nd standard/slowest, no mv, pv low, b-frames, no gmc, no qpel

3-pass:
VDubMod, same settings as above, 1st/2nd/3rd standard/standard/slowest, no mv, pv low, b-frames, no gmc, no qpel

Anything wrong with that settings?

DarkWave

[temporance]

Did you accidentally use the output of the 2nd pass as input for the 3rd pass?

[DarkWave]

what i did, was the following:
- i converted the dvd2avi output with VFAPIConv so vdub could handle it
- edited the params for 1st-pass (btw with 4000KBits/s), added it as film.avi to the job-queue
- edited the params for the 2nd pass (920KBits/s), then again added it as film.avi to the job-queue
- 3rd pass, same as 2nd pass - changed only standard to slowest mode, and again, saved it as film.avi
- then i opened the jobs-menu and started the whole queue...

was it wrong to use 920KBits/s in 2nd AND 3rd pass? must i only use it in 3rd pass and give 2rd 4000KBits/s?

DarkWave

[kl33per]

All passes should use the same bitrate.

[DarkWave]

Originally posted by kl33per
All passes should use the same bitrate.

sure? in all guides you find informations, that the 1st-pass uses a higher bitrate than the other passes...or did i misunderstood these guides?

[N_F]

Originally posted by DarkWave
sure? in all guides you find informations, that the 1st-pass uses a higher bitrate than the other passes...or did i misunderstood these guides?

While the codec does indeed do something like that, it'll do it automatically without your input. You should use the same bitrate for every pass.

[DarkWave]

Hi,

@kl33per & N_F
thx for your comments. for me it was clear to use the same bitrate in the nth passes, but ´cause of the possibility to enter a value for the first pass, i thought i had to do it manually.

but the old problem is still there: macroblocks in a 3-pass encoding, even when using a denoiser (source is a bit noisy - stargate sg-1 1st season box).
3-pass leaves less artifacts around people or objects, but produces more blocks, especially in scenes with a high amount of blue colors...

EDIT: you can find some screenshots here... (http://members.lycos.co.uk/muliekino/sg/)

DarkWave

[Acaila]

Actually AFAIK when doing the first pass, the codec encodes it with the bitrate you specify, not with 'extra high quality'. That way it will gather the complexity/motion information for the correct bitrate so the 2nd pass won't deviate too much from the known info.
GordianKnot on the other hand performs a compressibility test with a constant quant 2 file, not with a normal 1st pass file. Also, XviD's 1st pass is done with a constant quant 2 encode as well, not bitrate mode like DivX.

[N_F]

I've been away too long... I had XviD in my mind while writing that.