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[MPEG-4 Video Export Options
When you export a movie to MPEG-4 format (by choosing File > Export and then choosing Movie to MPEG-4), you access the following options by clicking Options and then clicking Video. File Format: To ensure operability with devices made by ISMA members, choose MP4 (ISMA). For more information, go to www.isma.tv.Preserve Aspect Ratio Using: If you are changing the image size, use this option to
specify an option in case the movie needs to be scaled to the new dimensions.
Letterbox will scale the source proportionally to fit into the clean aperture, adding
black bars to the top and bottom or sides as necessary. Crop centers, scales, and
trims to the clean aperture. Fit Within Dimensions adjusts to the destination size by
fitting to the longest side, scaling if necessary.