Apple MPEG Media System: Can't Copy Part of an MPEG Movie

TECHINFO-0020655

TOPIC

I am using the Apple MPEG Media System and MoviePlayer to play a MPEG movie file. I copied a small part of the movie to a new MoviePlayer file, but when I save it as a self-contained movie, it saves as the same size as the original movie. If I saved it normally (with dependencies), the file size is small but cannot be played without the original MPEG movie. Why?

DISCUSSION

There is an inherent limit with MPEG which disallows a subset of the whole video to be moved out by itself. It is possible to extract only the parts you want to use, but it requires writing code to go and get certain required overhead information from the MPEG movie. So, it is possible to make a smaller subset of a larger video, but only if extra code is written. Without writing code, as you have discovered, when you copy a sequence from a MPEG video and save it as a self contained movie, it will be the same size as the original.

If you do not make an edited movie self-contained (not flattened), you have a "chapter marker" movie. Since the default save mode of Movie Player is a reference file (not a flattened/self contained file), the default movie format is very small since It is only a reference to a location within the full MPEG movie file.

Important: You cannot copy a MPEG movie from a video CD (CDi) to a hard disk for playback. The block sizes of the CD-ROM disc and hard drive are different, so checksums will not match.

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