VP6 Undersize

[Ninokun]

I have a little problem. When i'm encoding video with VP6 (both simple and advance profiles), i'm always get my output file undersized. I'm use 6.0.9.2 version of VP6 and VirtualDub 1.5.10. I'm only interesting and try 2-pass encoding.

For example:

Source file: 29411 frames, 23,976 fps
Target video only size must be 128 MB
So bitrate must be 128*1024*23,976/29411=107 kilobytes/seconds

BUT, with whis bitrate my output filesize is around 120-123 MB. Maybe i do something wrong. Thanks for help.

[DevilsChild]

I have also been getting undersized files with VP6. Part of this may be due to roundoff error (VirtualDub won't let me enter a noninteger bitrate) but I suspect something else may be wrong...