Do re-rendered AVI files loose quality?

hmartine_67 wrote on 9/14/2003, 4:27 PM
If I have an original AVI file and I edit it by cutting parts of it that I dont like,
will the the new edited AVI file loose quality if I re-render it to the same format?
A good way to say what I am trying to ask is... like when you compress WAVE files to MP3s, we all know that there is loss in the quality of the file. Is it the same situation with avi files??

Thanks.

Comments

Chienworks wrote on 9/14/2003, 5:25 PM
Here's the formula:

First, anything that alters a frame in any way will cause it to be decompressed and recompressed, resulting in a (very small) loss in quality. These changes include fades, brightness, color correction, effects, compositing, titles, cropping, rotation, movement, etc. Simple cuts and splices don't alter the frames left behind so cuts won't introduce a need for de/recompression since the frames will simply be copied bit for bit.

The straight copying only applies for certain file types. There are three combinations of input and output files that will be copied instead of being de/recompressed. These are:

- Uncompressed AVI -> Uncompressed AVI
- DV compressed AVI -> Uncompressed AVI (well, this still involves decompression)
- DV compressed AVI -> DV compressed AVI

Any other combination will require recompression and the resultant loss in quality.
hmartine_67 wrote on 9/15/2003, 10:41 AM
>>"..anything that alters a frame in any way will cause it to be decompressed and recompressed... Simple cuts and splices don't alter the frames left behind.." You answered my question right here, because that's what I am trying to do. I copied anolog video, using DV pass-through. We all know that by doing this, VF/ScreenBlast does not detect the end of clips and it does not start a new clip file everytime. So, I have a twenty minutes movie clip. I want to come back and split big files and save smaller files out it. That was my concern about loosing quality if I saved the new clips to new files.

Chienworks, thanks a lot for help in the matter. I really apreciate it.