We should say that the ‘trak’ sub-parameters are as defined for the identified sample entry type when for the codecs parameter in 14496-12; similarly for the item type, when it is identical to a sample entry type for part 12. We need to think about operations, is it oper+oper+hvc1, for example? The hvc1 might need sub-parameters. Open questions: what to do about derivation chains, and sub-parameters for an item that does derivation.
m35038 A Sample Group for Reference Picture Identification in 23008-12
We like this for image sequences, where the number of reference pictures is likely to be small (delta sample numbers might work better in video). Also, this allows deleting some images without altering the group. The non-0 sample_ID groups must be linked to exactly one sample (one sample is a member). And we prefer 0 as the reference count for non-depending samples.
