n-pass questions?

[george_zhu]

I once saw people in this forum said xvid did not need any 3rd or 4th pass and the other codecs needed it probably only because they did not tweak it enough. I thought there are some things in setting can only be decided in the end, like VHQ. How does the algorithm decide to spend the saved bits? It looks one needs one more pass to rearrange it. Am I right? Or all these things has been done in the 1-pass?

In my encoding process (2-pass), the 1-pass is about the 60fps while the 2-pass is about 35 fps. Is that normal? I used to do the DivX, which usually has the similar speed on every pass.

[kadajawi]

About your second question, yes, its normal. Allthough your results are very fast :) They deactivated a few flags in the first pass because they are not important for the second pass. So it got faster.

[Mug Funky]

to be honest, i have no idea why encoders would need more than 2 passes. but i don't have the answer ready for you...

[symonjfox]

Originally posted by Mug Funky
to be honest, i have no idea why encoders would need more than 2 passes. but i don't have the answer ready for you... I got it.
Adding nth passes is a nice workaround for a not well tuned 2 pass implementation.

In theory, if the first pass analizes in a good way, the second pass just have to encode the final stream, so other passes are just a waste of time. Instead using DivX or CCE, a third pass increase the quality quite a lot.
IMO Xvid is smart enough and 2 passes give beautiful results.

[chilledoutuk]

logic says that if xvid had nth pass encoding its bitrate alocation could be further improved just like cce and divx.
I dont think its likely that xvid is perfect at 2pass bitrate alocation that it would not benifit from extra passes.

[Prettz]

Originally posted by chilledoutuk
logic says that if xvid had nth pass encoding its bitrate alocation could be further improved just like cce and divx.
I dont think its likely that xvid is perfect at 2pass bitrate alocation that it would not benifit from extra passes.
well its bitrate allocation is a whole hell of a lot better with 2 passes than Divx 5's is with 3, so xvid is clearly doing something right.

[temporance]

Originally posted by Prettz
well its bitrate allocation is a whole hell of a lot better with 2 passes than Divx 5's is with 3, so xvid is clearly doing something right. Really? My experience is that they are equivalent after 2 passes of each.