Showme plays on an 8 bit colormap. Mtv plays in TrueColor and can be run as a netscape plugin. Usually we do not simply want to make mpeg's from directly captured video. At our department we use AVID Media Suite Pro, running on an Indigo 2. The internal file format of media suite is omf.
Omf files can contain video and audio clips and editing lists, and have lots of bells and whisles.
The quality loss during this process is significant. Output must be a seekable file, as omf2sgi writes in two passes. Of the input files, only the audio file needs to be seekable. Thus the video file can e.g. be read directly from a backup tape. Performance of the converter was measured on local disks of a Sun Enterprise server.