Xvid Brightness & Contrast Control

[turbines]

I have some good copies of some old B&W movies that have been compressed using Xvid and DivX. The problem is that all frames are rendered too dark and important details are missing. I would like to edit these using Virtualdub or some other application that allows the use of brightness and contrast adjustments and then save the file with approximately the same size and quality as the original. I know that I can use the B&C filters in VD but I also see that the Xvid encoder has a brightness slider in it's configuration properties that can be used with fast recompress as opposed to full processing. Is there any advantages to using fast recompress? Can someone explain the best way to do this?

[LoRd_MuldeR]

"Fast recompress" will connect the Decoder directly to the Encoder with no video filters in-between.
This avoids unnecessary color-space conversions and thus should speed-up the re-encoding.
But in your case "Fast recompress" won't be suitable, because you obviously need to use a filter ;)

Nevertheless in your case I would re-encode the videos in Avidemux.
It has all the filters you will need and you can set the Xvid encoder to "Same Qz as input" mode.
The latter should give you approximately the same output quality as the input was.
AFAIK the VfW interface of Xvid does not offer "Same Qz as input", so you can't use that option in VDub!
Of course re-encoding always kills some quality, but that can't be avoided :(

Only way to avoid re-encoding and keep 100% quality is:
Keep your video as-is (no re-encode) and correct the brightness/contrast at playback time!

[turbines]

This was helpful. Thanks

[turbines]

Another question. What is I wanted to maintain approximately the same size file whilst sacrificing quality a bit? The original is about 714 MB and I would like to the filtered re-encoded version to also fit on a CD-R

[LoRd_MuldeR]

Another question. What is I wanted to maintain approximately the same size file whilst sacrificing quality a bit? The original is about 714 MB and I would like to the filtered re-encoded version to also fit on a CD-R

Use Xvid in "2-Pass" mode and set the target files size to 700 MB.
This will give you the maximum quality for the given size :)

If you use Avidemux, see my comment "How can I set the target filesize (e.g. 700 MB) in Avidemux?" in the FAQ:
http://forum.doom9.org/showpost.php?p=1006659&postcount=1