For archiving videos where quality loss is to be avoided, use lossless codecs

Example of lossless video codecs

FFv1
Huffyuv
Lagarith
x264 in lossless mode.

Note that generally lossy codecs is used to keep file size down. (for example h264 is usually encoded in lossy mode where some data is discarded)

Also, to maintain audio quality, also use lossless audio codecs such as flac. MP3 and AAC are common lossy audio codecs where some data is discarded.