Adobe ENCORE 2 Manual page 32

Average asset size
Use the following averages for bit budgeting:
If compressed using the Dolby Digital Stereo standard, audio is generally 192,000 bps (0.192 Mbps). Use 0.192
Audio
Mbps or reference the settings for the audio encoder you plan to use.
Insignificant in terms of bit budgeting, unless you include subtitles. If you do include subtitles, use
Subpictures
0.010 Mbps per subpicture stream for calculations.
Typically have a data rate of 8 Mbps for the transcoded video; add this to the audio data rate. (If the
Motion menus
video is already DVD-compliant, then it won't be transcoded, and you should use the data rate of the video file.)
Typically insignificant in terms of bit budgeting and can usually be left out of the calculation. Still menus
Still menus
average 230 Kb in size.
The asset size for a slide show depends on whether you include transitions or the Random Pan Zoom
Slide shows
effect:
•
If the slide show contains no transitions or effects, the slides are written to the DVD as MPEG stills, which require
minimal space. Stills average 230 Kb in size, which is typically negligible for bit budgeting. If you have a large
number of images, however, you should include them in your calculation.
•
If the slide show includes transitions, then Encore DVD writes both stills and transcoded MPEG video files for
the transitions. For example, if a given image appears for 10 seconds, with a two-second transition at the beginning
and the end, then the still is written to the disc (displayed for six seconds) as well as two 2-second MPEG video
files that contain the transition frames.
•
If the slide show includes pan and zoom, then Encore DVD transcodes the stills into an MPEG video file. Slide
shows with pan and zoom, in essence, become video content and require the same space allotment as video files.
For example, a five-minute slide show that uses pan and zoom throughout counts as five minutes of video content
for bit-budgeting purposes.
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.
Calculate the disc space available for video. Combine the size of the audio, subtitles, motion menus, and 4% of the
2
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 36,096,000,000 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. 36,096,000,000 bits / (133 minutes x 60 seconds/minute) =
4,523,308.27 bits/second. Divide the bits/sec amount by one million bits/Mbit to convert the video data rate to Mbps.
4,523,308.27 / 1,000,000 = 4.5 Mbps (Megabits per second).
Determine the maximum video data rate. Subtract the combined audio, subtitles, and motion menu data rates,
4
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.
So the video will fit on the disc using a data rate of 4.5 Mbps. 4.5 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.
ADOBE ENCORE DVD 2.0 27
User Guide