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Unofficial VirtualDub Support Forums > Newbie Questions > Bitrate Setting Has Little Effect

Posted by: curmudgeon Oct 12 2002, 05:11 AM

Hi. I already posted this in the everwicked DIVX forum, but
thought I could crosspost in at least one forum here (and this
one seems as good as any

).

Some details:

Latest versions of Virtualdub and Divx.
Windows 2000 machine with boatloads of RAM and CPU.

Have a 45 minute AVI (17.2 GB) I want to compress to
225-240 MB using Divx.

Have Variable bitrate mode to "1 pass."

Set encoding bitrate to 640 kbps, get 330.9 MB file).
Set encoding bitrate to 480 kbps, get 326.4 MB file).
Set encoding bitrate to 320 kbps, get 325.8 MB file).

I have pretty much left everything else at the defaults.

Can somebody explain this? 640 kbps should give
2700 sec X 80 kBps = 216 MB (plus 10 MB for audio),
but even with a bitrate of 320 kbps, the Virtualdub
info window shows more than 100 kBps while encoding
(the MP3 audio totals about 7 MB).

Thank you in advance.

Posted by: fccHandler Oct 12 2002, 05:34 AM

MP3 audio is 7 MB for a 45 minute video??? (Hard to believe)

Anyway, I'm not sure why you are getting those results. You could try 2-pass encoding and see if it comes out differently.

BTW: "1-pass" is CBR, "1-pass quality-based" is VBR.

Posted by: BaronVlad Oct 12 2002, 08:27 AM

I dont know exactly, but maybe this could be your problem (Dont care about GKnot, the problem is codec related):

http://gknot.doom9.org/faq-general.html#gq8