I would like to know if is it possible to increase the brightness or gamma of a video without full re-encoding. For example some versions of ffmpeg allow certain special bitstream filters described here - presumed we have a h264 video - :
http://forum.doom9.org/showthread.php?t=152419 which can alter some of the video characteristics without re-encoding the video. Some containers also can store such a meta information about the video gamma or brightness, as far as I know matroska, and QuickTime, and maybe there are some video players too which can deal with this information. I know that a similar modification, namely cropping the video is possible without a full re-encode merely by setting the cropping information at container level.
For example such a video uploaded to youtube are cropped at the values which were set at the container level. So this could be a quick fix for unneeded logos and black bars.