Generate Sample Encryption Information Box for Storage of Sample Auxiliary Information

[kqyang]

CENC v2 introduces an optional box to store Sample Auxiliary Information: Sample Encryption Information.

The Sample Encryption Box contains sample auxiliary information, including the initialization vector for each sample, and clear and encrypted byte ranges of partially encrypted video samples (“subsample encryption”). It MAY be used when samples in a track or track fragment are encrypted. Storage of ‘senc’ in a Track Fragment Box makes the necessary Sample Auxiliary Information accessible within the movie fragment for all contained samples in order to make each track fragment independently decryptable; for instance, when movie fragments are delivered as DASH Media Segments.