recompressing without losing quality and keep the size????

[Fking]

I have a mpeg, Gspot says it's MPEG1Payload

i need to add a logo and split it into smaller pieces, i'm using virtualDUB-MPEG, trying with different conversions (XViD MPEG-4, DivX MPEG-4 fast motion) methods but always the output files are bigger than the source file (with around 50%)

gspot can't tell me what's the frame rate and the bitrate of the source file


so here are the questions
- how to understand what compression method to use with what options in order to get the same quality in the same file size or smaller
- is there a way to tell virtualdub to split the whole file in equal 2mins pieces (now i'm doing it manual)

[Baldrick]

change the audio and video bitrate to change the output size. xvid has a built in bitrate calculator.

[Fking]

thank you, but how to understand how low i can go, without losing quality?

[junkmalle]

If you don't care about the exact size of the final file use XVID's Quantization mode. This is a constant quality setting. You pick the quality you want and then encode.

You'll probably want somewhere between 2 and 4. At 2 you will be hard pressed to see any differences between the input and output, even in still frames. At three you'll see a little difference in still frames but it won't be noticable at normal playback speeds. At 4 you'll be able to see minor differences at normal playback if you look closely.