Bitrate is not as high as it should be in XviD

[nonoitall]

I'm using VirtualDubMod to do a two-pass encode on a (about an hour and 45 minutes) video and have a target bitrate of 1680 kbps for the video part (which I have set in the codec). However, the final encode ends up being around 1600 kbps, which makes the file smaller than is preferable. Any tips on getting the size a little closer to my desired rate?

[celtic_druid]

1. What is or would have been (could have discard 1st pass enabled) the size of the 1st pass?
2. Are you capping quants?
3. To do with 2, what build of XviD are you using? Older builds by default capped quants to 2-31. Newer ones have it set to 1-31. With 2-31 a 2nd pass can't be larger than the 1st.

[nonoitall]

The first pass had a rate somewhere in the 17 or 18 hundreds (don't remember exactly what it was), so it definitely can go up to 1680 kbps. On first and second passes all types of frames had 2-31 quantizer limits. And I'm using XviD build XviD-1.1.0-Beta2-04042005 (which I think is the most current beta). Thanks for any suggestions - as you can probably tell I'm a bit of a newbie.

[celtic_druid]

You must have changed the settings to 2-31 then since the default is 1-31.

Beta2 is indeed the latest beta. There have been quite a few changes since it though.

Still sounds like a case of the encoder becoming saturated. You might want to varify the size of the first pass to check.

Personally I have always used the size setting for 2 pass encodes and it has always been very accurate.

[nonoitall]

Will give that a try and let you know how it turns out in the morning. Thanks.

[nonoitall]

That got the average up to 1637. If there aren't any more suggestions to get it closer that will probably work okay.

[manono]

Hi-

This is all pretty basic stuff which you should know already. If your first pass bitrate was 17-1800, as you say, then you're not taking advantage of the MPEG-4 compression abilities if you want a final bitrate of 1680. You've saturated the codec, as celtic_druid says. You can raise the resolution, use a sharper resizer (Lanczos, instead of Neutral Bicubic, for example), turn off the B-Frames, give the AVI better audio (AC3, instead of MP3, for example) so the video bitrate is lowered, knock off any filtering you may be using, etc. Personally, I would never place myself in a position where I needed to use Quant 1, and as celtic_druid, I always get the final size I aim for .

[celtic_druid]

I'd leave bframes enabled, but use a higher quality quant matrix.

[nonoitall]

What's a good one?

EDIT: Also already using Lanczos and the highest resolution possible.