Apple DVD Studio Pro 4 - Manual (Page 639)

For the DVD-5 disc, you need to subtract the total audio amount from the total disc size:
37.6 gigabits – 7.684 gigabits = 29.916 gigabits for the video. Dividing the available space
by the video duration provides a new bit rate: 29.916 gigabits ÷ 7926 = 3.77 Mbps. You
can see that the audio has considerably affected the original bit rate for the DVD-5 disc
(4.74 Mbps). The use of PCM audio for the second video asset in this example has forced
the video bit rate to drop below 4 Mbps, making the use of a DVD-5 disc questionable
because a bit rate that low may not provide suitable quality.
For the DVD-9 disc, you end up with 60.636 gigabits available for the video (68.32 gigabits
– 7.684 gigabits). The adjusted video bit rate is now 7.65 Mbps (60.636 gigabits ÷
7926 seconds)—easily high enough to provide good quality.
Stage 6: Calculating DVD-ROM Allowances
If you intend to include DVD-ROM content on the disc, you need to subtract it from the
disc space before coming up with your video bit rate.
Because the size of your DVD-ROM content is expressed in binary megabytes, you must
convert it to the same standard as used for the DVD disc size. In this example, there is a
total of 36 MB of data. Each computer MB is equal to 1,048,576 actual bytes. To convert
the DVD-ROM content, you need to multiply its size (36 MB) by 1,048,576 to get the actual
size of 37,748,736.
The next step is to convert this number into bits by multiplying it by 8, providing a final
size of approximately 0.3 gigabits. While this is not a large amount of space, you should
take it into account if you are trying to maximize usage of the disc’s available space.
Stage 7: Calculating Other Allowances
There are several other factors that should be taken into account when determining
available disc space.
• Slideshows: Each still in a slideshow requires approximately 200 kilobytes (KB) of disc
space. A full slideshow with 99 stills requires about 20 MB of disc space. If the slideshow
contains audio, you will find that the audio can require as much or more disc space
than the stills. If your disc contains many stills, you will need to take them into account.
• Still menus: Each standard still menu requires about 300 KB of space, depending on
the number of buttons.
Layered menus can require a lot more space than standard menus because a new menu
is created for each button in each of its separately specified states (normal, selected,
and activated). This can mean as many as 12 menus are created to support 4 buttons.
See
Creating Menus Using the Layered Method for more information on layered menus.
Note: Menus that use button shapes with motion assets assigned are considered to
be motion menus, and need to count as a video asset.
639 Appendix C Calculating Disc Space Requirements