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Referencing Two Data Files With a Single Track

The data reference index to be used for a given media sample is stored within that sample’s sample description. Therefore, a track must contain multiple sample descriptions in order for that track to reference multiple data files. A different sample description must be used whenever the data file changes or whenever the format of the data changes. The sample-to-chunk atom determines which sample description to use for a sample.

The sample description atom would contain the following data values:

If there is only 1 sample per chunk and the first 10 samples are extracted from sample description 2 and the next 30 samples are extracted from sample description 1, the sample-to-chunk atom would contain the following data values:

The data reference atom would contain the following data values:

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