Writing an MP4 Muxer for Fun and Profit | OBS

by Rodney July 12th, 2024

(Except there is no profit, only pain)

In OBS 30.2 I introduced the new “Hybrid MP4” output format which solves a number of complaints our users have had for pretty much all of OBS’s existence; It’s resilient against data loss like MKV, but widely compatible like regular MP4.

Getting here was quite a journey, and involved fixing several other bugs in OBS that were only apparent once diving this deep into how the audio and video data is stored.

In this post I’ll try to explain how MP4 works, what the drawbacks were to regular/fragmented MP4, and how I tried to solve them with a hybrid approach.

And at the end of the document:

Thanks & Acknowledgements

NOT the ISO for paywalling these specs and making it a god damn paperchase where every time you get one document it references three others that are also paywalled