4.0

The image buffer
A new concept for DVD authors is managing the image buffer for the graphics you include in menus. In
DoStudio Authoring, this includes your pop-up menus and your First Play image.
DoStudio Authoring creates all of the pop-up menus as BD-J (Blu-ray Disc Java) so you can use 32-bit
graphics. The image buffer size varies depending on the profile of the Blu-ray Disc player. BD-J allows a
maximum graphics buffer size of 45.5 MB for profile 1.0/1.1 players and 61.5 MB for profile 2.0 players.
These numbers are misleading, however, because you cannot cram 45.5 MB of graphics into the buffer and
expect your disc to function properly on many Blu-ray Disc players due to the overhead of processing the
graphics.
We have found though extensive testing that all players can handle 32.5 MB of graphics buffer and
DoStudio Authoring limits you to 32.5 MB so that your discs will play successfully on all players. When you
compile your project or run the validation in the Control Panel, DoStudio Authoring calculates the total file
size for each menu element and warns you if you have exceeded the 32.5 MB limit.
How is the image buffer size calculated?
The size of the image buffer is based the fact that each pixel in an image uses 4 bytes of memory. This is
because every pixel uses four colors: red, green, blue, and an alpha channel to determine the color and
transparency of the image. The equation for calculating the image buffer size is as follows:
Width x Height x 4 = number of bytes
For example, an image that is 1920x128 image takes up 124 KB of space:
1920 x 128 x 4 = 124,000 bytes
Tips for managing the image buffer size
n Do not create images with a lot of extra transparencies around the actual image. Even a
transparent pixel takes memory.
n Create a small first play image, such as the text loading.
n Reuse a background image for all sets by placing the background image on the menu block instead
of on each set.
n Remove any images for the selected and activated state that are not being used.
n Keep in mind a wide image that is applied to a set can be used to remove a lot of extra pixels from
memory.
n Keep in mind an image that is 512 pixels by 256 pixels will take up 1 MB of image memory.
n Design your menu using rectangles and keep track of a rough estimate of how many bytes each
rectangle will use. Remember buttons have up to three images per rectangle.
DOSTUDIO AUTHORING BASICS13