I have an MPEG1 video I would like to convert to either Divx or Xvid.
Is there a way to calculate the optimal bitrate I should use?
Maybe the 1st pass can tell me that?
To convert to MPEG4 (DivX/XviD) you do not easily choose a bitrate, you choose a target size ie. 700MB (1 CD) incl. audio.
The encoder ie. GordianKnot will then calculate the precise bitrate that, combined with the audio and interlacing overhead plus any other extra files you wish included, will total 700MB.
Most AVI tools expect to work from MPEG2 DVD - to transcode from MPEG1 is trickier, the 'easy' tools like GKnot are not designed for this.
You may have to do it manually using VirtualDubMod ;^(
Work backwards from 700MB, subtracting the audiosize and calculating the bitrate to achieve the proper filesize using one of the freely available bitrate calculators.
The calculation is basically bitrate x minutes = 700MB
If you know the last two, you can calculate the first :^)
Hope this helps,
L8R
Calculating bitrate by target size is not new to me, however I thought there might be a better way, because guessing the optimal target size is about the same as guessing the optimal bitrate.
I've tried to halve the size of the MPEG1 and it worked without visible quality loss. I was wondering if halving the size is not just an "instinct", maybe there's an algorithm that can analyze the file and choose the bitrate.
