An AVIF Is an MP4 With One Frame

GIF's structure was a header, some tables, and a sequence of blocks with a one-byte type code. MP4 is stricter than that, and the strictness is the whole design. Every byte in the file lives inside a box, and every box starts the same way: 4 bytes size, big-endian, including this header 4 bytes type, four ASCII characters That is it. Eight bytes, and any parser that knows nothing else about the…