2nd pass capped at quant 4? celtic_druid's xvid.cvs.head.2005.01.10

[Mug Funky]

something's odd - my 2-pass encodes have started capping themselves at quant4, and seriously undershooting the bitrate target.

i haven't changed the quant ranges. the only thing i touched outside the defaults was turning AQ on, and setting the profile to a AS level 0 and 2 (which i then changed back to unrestricted and a number of other profiles).

i re-installed (and tried a couple different compiles, all of the same CVS date), but haven't been able to get my quant 2's back on 2 pass mode.

[edit] oops, it seems to be using higher quants now, but only quite far into the encode, and now it's seriously overshooting the bitrate i set without increasing quality. this is strange.

[edit 2] tried a different encode and it came out capped at 3, and undershot the bitrate. very strange. i'll try to find what's causing this.

[edit] tried some anime and ratecontrol works pretty much perfect (within +- 2kbps). strange that it's choking on DV footage, downsized or not. will try more samples.

Okay here's what i'm noticing - as noise level increases, final bitrate gets lower. i'm experimenting with AddGrain, and it seems to bear this out. i'm using short clips (about 1000 frames) to test.

[Sharktooth]

1000 frames is not enaugh for testing.
However it seems the last builds have hard times hitting the correct final filesize.
Sometimes i have to compensate, something i never did with older builds...

[Mug Funky]

yes... that's what i was getting at. i wanted to know whether other people were experiencing this before i went for some longer encodes - my machine is exceedingly slow, and i think a large variety of sources need to be tested.

at the moment i think it's just the noise level that's screwing things up, but it could be something else. indeed, xvid is typically used with very clean sources - usually filtered DVD rips, and i'd wager most of that is anime. i guess we've got to start throwing some different stuff at it and seeing what happens.

but yes, i've never had a problem with ratecontrol before, hence my confusion.

[Sharktooth]

Well i have made many DVD backups (both anime and movies) with xvid and got an excellent quality, but honestly i have no video capture devices and i never tried to encode that materials.
Noisy and grainy sources (old movies) can create some problems but usually i do those backups with VP6 (now i'm trying with nero digital too).

[Mug Funky]

what's strange is the last backup i did was reasonably grainy and was spot on. i think this might be a recent occurence in xvid, but i'm not sure how recent (1.0.3 seemed to have been behaving the same, so i think i'll have to use longer clips to confirm)