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Creating Video Tracks at 29.97 Frames per Second

NTSC color video is not 30 frames per second (fps), but actually 29.97 fps. The previous example showed how the media time scale and the duration of the frames specify the video’s frame rate. By setting the media’s time scale to 2997 units per second and setting the frame durations to 100 units each, the effective rate is 29.97 fps exactly.

In this situation, it is also a good idea to set the movie time scale to 2997 in order to avoid movie edits that don’t land on frame boundaries. The movie’s time scale is stored in the movie header atom.

With a time scale of 2997 in the media header atom, the time-to-sample atom would contain the following data values:

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