CODEWITHSUNDEEP
videomp4h.264
misterbiscuit
misterbiscuit

Reputation: 1797

Why does the AVC Decoder Config Record ISO 14496-15:2004 5.2.4.1.1 use arrays of multiple Sequence and Parameter Sets?

Why does the AVC Decoder Config Record ISO 14496-15:2004 5.2.4.1.1 use arrays of multiple Sequence and Parameter Sets?

It seems logical that you may have multiple different configurations in one track but how is the configuration for a specific period of time referenced in this index? Is there something in the H.264 spec which defines this or is it specific to the MP4 container?

Upvotes: 1

Views: 464

Answers (1)

Markus Schumann
Markus Schumann

Reputation: 8244

The Sample Description Index (one based) is used to choose the correct AVC Decoder Config Record. For any given sample you look up the index in your MP4 file 'stbl' -> 'stsc' -> entry[].sample_description_index. Based on the sample_description_index you choose the AVC Decoder Config Record. An AVC Decoder Config Record can contain multiple PPS and SPS. The slice header of a video coding unit inside the AVC stream contains the pic_parameter_set_id that references the correct PPS. The PPS contains seq_parameter_set_id referencing the correct SPS.

Upvotes: 2

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