How can I determine the CODECS value for a m3u8 playlist?

Question

I am creating a master m3u8 file to allow adaptive streaming of two streaming videos. Both have the readable codec name MPEG-4 AVC (part 10) (avc1)

How can I translate this into the CODECS value that should appear in my master m3u8 playlist file, as in this example:

#EXT-X-STREAM-INF:PROGRAM-ID=1,BANDWIDTH=1755600,CODECS="avc1.42001f,mp4a.40.2",RESOLUTION=354x240

How do I get the value to replace avc1.42001f,mp4a.40.2

Apple's specs say "Valid format identifiers are those in the ISO file format name space defined by RFC 6381 [RFC6381]" but I have no idea how to read the RFC 6381 documentation.

Answer 1

Each codec string is codec specific. For audio, mp4a indicate its mpeg audio 40 means its mpeg 4.0 (I think) and the last integer is the "audio object type". AAC-LC is 2. The full list can be found here. https://wiki.multimedia.cx/index.php/MPEG-4_Audio#Audio_Object_Types

For video, in your example case, The video codec is h.264, also known as "advanced video codec" aka avc1. The hex string is 3 bytes representing the codec profile, flags, and level. Those can be found in the first 3 bytes the the SPS.

Other codecs are different.