Video
What bitrate fits a 2-hour film on a 4.7 GB DVD?
4.8Mbps of video
5.22 Mbps in total for 120 minutes in 4.7 GB, minus a 448 kbps audio track. In practice leave a few percent for the disc's file system.
Working backwards from the space you have to the bitrate you can afford is how people encode for discs, upload limits and email. Remember the audio shares the same space.
The arithmetic
- 4.7 GB × 8 = 37,600,000,000 bits
- 120 minutes = 7,200 seconds
- 37,600,000,000 ÷ 7,200 = 5.22 Mbps for everything
- Less one Dolby Digital 5.1 audio track at 448 kbps (assumption): 4.77 Mbps for the video
| Running time | Total bitrate | Video bitrate |
|---|---|---|
| 60 min | 10.44 Mbps | 10 Mbps |
| 90 min | 6.96 Mbps | 6.51 Mbps |
| 120 min | 5.22 Mbps | 4.77 Mbps |
| 150 min | 4.18 Mbps | 3.73 Mbps |
| 180 min | 3.48 Mbps | 3.03 Mbps |