Sample budget #1


    Bit budgeting for a simple project containing 2 hours and 13 minutes of video, without any audio, to be distributed on a 4.7 GB disc proceeds as follows:

  1. Calculate the total available disc space in bits. A 4.7 GB (gigabyte) disc contains 4,700,000,000 bytes; each byte contains 8 bits. 4,700,000,000 x 8 = 37,600,000,000 bits.
  2. Calculate the disc space available for video. Combine the size of the audio, subtitles, motion menus 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. Since this example has no audio, subtitles, or motion menus, you subtract only the 4% for overhead (1,504,000,000 bits) to get a value of 37,096,000,000 bits.
  3. 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. 37,096,000,000 bits / (133 minutes x 60 seconds/minute) = 4,648,621.55 bits/second. Divide the bits/sec amount by one million bits/Mbit to convert the video data rate to Mbps. 4,648,621.55 / 1,000,000 = 4.7 Mbps (Megabits per second).
  4. Determine the maximum video data rate. Subtract the combined audio, subtitles, and motion menu data rates, zero in this instance, from the maximum DVD video data rate of 9.8 Mbps. 9.8 Mbps - 0 = 9.8 Mbps. Since this is very close to the maximum rate for DVD, you can lower it to 9.0 Mbps to be safe.
  5. So the video will fit on the disc using a data rate of 4.7 Mbps. 4.7 Mbps is low enough (below 6 Mbps) that you should use VBR encoding. The maximum video data rate for VBR encoding is 9.0 Mbps.