2nd pass bitrate adjustment possible?

[daniel]

a question: is it possible to re-calculate the bitrate for the 2nd pass on basis of the result of the 1st pass?

for example: before the 1st pass gknot says: 1000 kb/s
if you're doing the 2nd pass also with a birate of 1000, the file turns out to be too small, but if you had chosen 1013, the file size would be exactly the correct size

[DJ Bobo]

Possible, but not recommended ("bitrate accuracy may be degraded")

"if the variation stay within a 30% limit, say 1st pass 1000kbps, 2nd between 700kbps and 1300kbps"

BTW, I recommend reencoding the audio part instead of the video part if you get a smaller size than predicted.

[daniel]

what I actually mean is: is there sort of a test which can determine the exact new value of the bitrate for the 2nd pass?

is this possible by looking at the result of the 1st pass?

I hope I'm clear with the question...

[manono]

Hi-

If you're talking about something like GKnot's Modified Stats File for DivX3.11, or Koepi's StatsReader for XviD, then I don't believe there is such a thing for DivX5.

However, more to the point is why you're getting 8 MB or so undersized for a 1 CD rip, which is quite a lot. How are you calculating the bit rate in the first place? If you're using GKnot, are you making sure to tick the box for DivX5 and not use the bit rate for DivX3? Are all your rips equally undersized? Are you changing anything, such as filters, between the first and second passes?

[daniel]

well, they aren't 8 mb undersized; just a couple mb's (2 or 3)

- between 1st and 2nd pass i don't change anything
- in gknot i choose divx 5
- they aren't equally undersized

how do i determine the bitrate:
- first i encode the audio
- then rip the subtitles
- in gknot i choose 350 mb (buffy eps) and i select the mp3 file
under 'audio file' and the subtitles under 'add files'; muxing
overhead is on; i'm getting a bitrate arond 1000, but actually it
must be 1010 or something...

[manono]

Hi-

I've read of the undersized problem, but haven't encountered it myself. All I can suggest is to set the bitrate 1% over what Gknot tells you, and then adjust for the 2nd episode on the CD if the first episode comes out under-oversized. It looks to me as if you're doing everything by the book. Maybe someone else has a suggestion.

[DJ Bobo]

Complaining about +/- 2~3MB?! this is nothing to worry about, this is almost normal. Forget about it.

BTW, you won't ever see the difference between a 1000 and a 1010kbps encoding.

[daniel]

i know (btw sometimes i do have got eps with let's say 6 mb!)
but...i'm a perfectionist..... you know :)

and it isn't about the difference in quality (which you can't see) but it just looks better if something is exactly 350 mb instead of 346 for example...

[mikeson]

daniel:

1. Try divx4log method...
2. You can try encode movie and credits separately, so you can adjust final size (+/- few megs) by reencoding credits on higher/lower bitrate

[daniel]

thanks i will try the program!

[daniel]

hmm.. i'm experimenting with divx4log and read the doom9 guide for the program, but it's only about keyframes and deltaframes, not about b-frames

so how do i have to configure the settings on b-frames?

[mikeson]

divx4log 0.48 supports b-frames

[daniel]

Originally posted by mikeson
divx4log 0.48 supports b-frames

yes i know, but that isn't the problem: i just don't know how to handle the b-frame settings ('cause in the doom9 guide only the other frames are explained)

[mikeson]

@daniel:

I personally set divx4log as following:
- I-frame quantizers 2-2
- P-frame and B-frame quantizers 2-x (x depends on target bitrate), so B-frame quants to the same level as P-frame quants.
- I leave B mult untouched (so 2.00).

- for movie I use square quantizer distribution for all quantizers (it doesn't matter for I-frame quants, cause I set them to 2-2)
- for credits I use root quantizer distribution
- source always based on motion
- no trimming

[daniel]

thanks! i'm gonna try it!

[mikeson]

@daniel:

Don't forget to do 1st pass with quants 2-2 and bitrate 10000 and exact codec settings (Qpel,GMC,B-frames and PSY) in both passes, but I'm sure you know that ;)

[daniel]

Originally posted by mikeson
@daniel:

I personally set divx4log as following:
- I-frame quantizers 2-2
- P-frame and B-frame quantizers 2-x (x depends on target bitrate), so B-frame quants to the same level as P-frame quants.
- I leave B mult untouched (so 2.00).

- for movie I use square quantizer distribution for all quantizers (it doesn't matter for I-frame quants, cause I set them to 2-2)
- for credits I use root quantizer distribution
- source always based on motion
- no trimming

a couple of questions:
- are you using the same settings (with split settings) for slow and fast?
- is it good to check 'discard divx5 junk frames'?
- do you encode you movie and credits seperately?
- what does b-mult do?

[mikeson]

are you using the same settings (with split settings) for slow and fast?

I don't use splitting at all but if I would I won't use the same settings for slow and fast. But I would always use 2-2 for all I-frames.

is it good to check 'discard divx5 junk frames'

I'm not sure about this option so I would rather leave it unchecked. ;)

do you encode you movie and credits seperately?

Yes, I always do that, because you can do fine size tuning by reencoding credits to lower/higher bitrate.

what does b-mult do

It changes b-frame multiplicator. I recommend this article http://forum.doom9.org/showthread.php?s=&threadid=29140&highlight=bframe+multiplicator

[daniel]

hmmm.. i did the 2nd pass with the same settings of the 1ste pass (except the log i changed) and the file is way too big: normally 350 mb and now 496 mb!!
maybe i did something wrong, but i just changed the quantizers in divx4log and it indicated a bitrate of 1004 kb/s (same asgknot indicated without divx4log)

these are the settings:
- source: motion, 0%
- i-frames: linear
- p- and b-frames: square
- fps: 25
- b-mult: 2.00

- split settings:
- slow:
i-frames: 2,2
p- and b-frames: 2,4
- fast:
i-frames: 2,2
p- and b-frames: 2,6

at that moment i realised that these values are actually too low, but divx4log indicated the right bitrate so i just assumed it would be right

what did i do wrong? :confused:

[mikeson]

Can you send me both logs?
Which movie did you encode?
What was desired file size?

[daniel]

it was an episode of buffy the vampire slayer (43 min)
desired filesize was 350 mb
i uploaded the 2 logfiles
use winrar to extract them

http://members.home.nl/dvsanchez/log.rar

[daniel]

does anyone understand why the file is that big after the 2nd pass?

has anyone checked the 2 logs?

'cause i still don't get it...