please HELP with video codec

hi, i have a digital camera that shoots video in a zoran zrswjpeg format 320x240 pixel 20 frame/sec with 8bit-11k ccitt u-law mono audio.

my problem is whenever i crop, brighten or enhance my videos with sony vegas, premiere or arcsoft videoimpression - i cannot find a suitable format to save the new video into.

if i save it uncompressed, it turns out to be about 10 times larger in file size.
And the compressed formats that are any good also result in huge file sizes.
most compressed formats that give low file sizes show a real bad loss in picture & audio quality.

is there any way that i can save my video in the SAME format -codec that it originated & keep it the same/similar file size while maintaining quality?
vegas shows an option for saving with a zoran jpeg decoder, but always says it cannot save with the current render settings- no matter what i change them to.

please help,
thanks tim