DVD Authoring With Unix?

An Anonymous Coward, with an interest in the multimedia sector, asks: "DVD authoring may one day be the next test of 'what you can do with a computer'. Can a professional-quality DVDs be created using Unix software? Are there sufficient tools, commercial or otherwise, to handle all the phases? MPEG-1 encoding? Different sound formats? Overlays? Branching? NTSC/PAL? And what's the user to do if s/he wants to do something simple, like burn some stills to a CD-R?"