It also has requirements on the box tree structure and order and what boxes are required/optional. Then there are also mapping per codec (see https://mp4ra.org/

It also has requirements on the box tree structure and order and what boxes are required/optional. Then there are also mapping per codec (see https://mp4ra.org/ https://mp4ra.org/) that have additional requirements on boxes and how the samples should be encoded. For example PNG in MP4 is mapped by having a stsd (sample descriptor) box that has a mp4v format/box which itself should includes a esds (mpeg elementary stream descriptor) box which will include a decode configuration stating that the stream type is video and the object type is PNG. You can see a decode using fq (https://github.com/wader/fq https://github.com/wader/fq) of the file used in the poster here https://twitter.com/mwader/status/1596219922304360448 https://twitter.com/mwader/status/1596219922304360448 Hope that was helpful