Sample budget #2
Bit budgeting for a 120-minute video with three audio tracks, two subtitle tracks, two motion menus, and a one-minute movie preview to be burned to an 8.54 GB disc proceeds as follows: - Calculate the total available disc space in bits. An 8.54 GB (gigabyte) disc contains 8,540,000,000 bytes; each byte contains 8 bits. 8,540,000,000 x 8 = 68,320,000,000 bits = 68,320 Mbits.
- Calculate the disc space available for video. Combine the size of the audio, subtitles, motion menus, movie preview and 4% of the disc capacity (for overhead, just to be safe) and then subtract that sum from the total available space you calculated in step 1.
- Three 120-minute audio streams, two with a data rate of 0.192 Mbps and one with a rate of 0.448 Mbps: (2 x (120 min. x 60 sec/min x 0.192 Mbps) + (120 min x 60 sec/min x 0.448 Mbps) = 5,990.4 Mbits.
- Two subtitles with a data rate of 0.010 Mbps: 2 x (120 min x 60 secs/min) x 0.010 Mbps = 144 Mbits.
- Two 24-second motion menus with an estimated data rate of 8 Mbps: 2 x (24 sec x 8 Mbps) = 384 Mbits.
- One-minute movie preview with a data rate of 4.5 Mbps: 60 sec x 4.5 Mbps =270 Mbits
- 4% overhead: 0.04 x 68,320,000,000 bits = 2,732,800,000 bits = 2,732.8 Mbits.
- Total audio, subtitles, motion menus, preview, and overhead sizes: 5,990.4 Mbits + 144 Mbits + 384 Mbits + 270 Mbits + 2,732.8 Mbits = 9,521.2 Mbits.
- Disc space available for video: 68,320 Mbits - 9,521 Mbits = 58,799 Mbits.
- Calculate the data rate of the video. Divide the disc space available for video that you determined in step 2 by the amount of video (in seconds) the project contains. 58,799 Mbits / (120 minutes x 60 seconds/minute) = 8.16 Mbps.
- Determine the maximum video data rate. Subtract the combined audio and subtitles data rates from the maximum DVD video data rate of 9.8 Mbps: 9.8 Mbps - (0.192 + 0.192 + 0.448 + 0.010 + 0.010) = 8.95 Mbps.
So the video will fit on the disc using a data rate of 8.16 Mbps, which is below the maximum video data rate of 8.95. Further, since the target video data rate of 8.16 Mbps is above 6 Mbps, you do not need to use VBR.
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