Motion-JPEG (M-JPEG) is a variant of the ISO JPEG specification for use with digital video streams. Instead of compressing an entire image into a single bitstream, Motion-JPEG compresses each video field separately, returning the resulting JPEG bitstreams consecutively in a single frame.
There are two flavors of Motion-JPEG currently in use. These two formats differ based on their use of markers. Motion-JPEG format A supports markers; Motion-JPEG format B does not. The following paragraphs describe how QuickTime stores Motion-JPEG sample data. Figure 3-1 shows an example of Motion-JPEG A dual-field sample data. Figure 3-2 shows an example of Motion- JPEG B dual-field sample data.
Each field of Motion-JPEG format A fully complies with the ISO JPEG specification, and therefore supports application markers. QuickTime uses the APP1 marker to store control information, as follows (all of the fields are 32-bit integers):
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