Xvid is undersized in matroska

Xvid consistently undershoots by a meg or two when I use the matroska format. I vaguely remember that Xvid takes into account the AVI overhead which I guess matroska does not have, so I guess I am asking whether is anyway to make xvid not assume an AVI output or fix this in some otherway.

use Gordian Knot for filesize/bitrate calculations, it can do the mkv overhead estimate and other things for you.

no I know and I do use gordian knot, and I still get undersized files. I think the problem is that XVID also does overhead prediction based on the AVI format, but when the xvid stream is muxed into an MKV it is too small. For example i recently encoded a movie where the target size of the video was 663242KB according to GKnot but the mkv with just the video stream was 661790KB i then muxed it into an avi and it was 663112KB. Which is pretty damn close to the target bit rate.

as this might be a problem with GKnot's MKV bitrate calculations I'm moving this to the GKnot forum.

You have to check carefully which overhead settings you're using in "Interleaving and AV-Overhead" section.

i thing rob is right... just check gknot calc and xvid calc... for the same settings of course example: 2h video on 1cd - 716800 kb (no audio) gnkot - 716800 target video size xvid - 718461 target video size bye

yes, XviD indeed has AVI overhead taken into account when producing video stream...