Difference between FourCC codes "avc1" and "avc3"? avc1 with sound prob?

[mike23]

What is the difference between the two "FourCC" codes "avc1" and "avc3" (when encoding AVC H.264)?

I got the impression that a FourCC "avc1" causes occasionally audio output problems when playing MP4 videos on (some) Android Smartphones.

If I encode the video with "avc3" and same other parameters then audio is working

[benwaggoner]

I found this via Google (https://stackoverflow.com/questions/28213793/how-do-i-know-the-structure-about-avc3-of-mp4-box#:~:text=The%20sample%20description%20entry%20%27avc3%27%20is%20structurally%20identical,find%20the%20definition%20in%20ISO%2FIEC%2014496-15%203rd%20edition.):
The sample description entry 'avc3' is structurally identical to the 'avc1'. The difference is only in the semantics: in 'avc3' streams the parameter sets can be in band, in the IDR samples. You can find the definition in ISO/IEC 14496-15 3rd edition.