Wikipedia dixit :

Video (MPEG2)

• 16 kbit/s — videophone quality (minimum necessary for a consumer-acceptable "talking head" picture)
• 128 – 384 kbit/s — business-oriented videoconferencing system quality
• 1.25 Mbit/s — VCD quality
• 5 Mbit/s — DVD quality
• 15 Mbit/s — HDTV quality
• 36 Mbit/s — HD DVD quality
• 54 Mbit/s — Blu-ray Disc quality