Feature Request - MP4 bitrate control property

[Charles Wiltgen]

Urs,

> …I have not found any information about such an "acbf" atom. Could
> you please give detailed information such as a link to a specification
> where exactly this information can be found in m4a files?

`acbf` is a custom atom written by Apple's Core Audio framework. The
integer values map to kAudioCodecBitRateControlMode constants in Apple's
AudioToolbox framework, documented in Apple’s Technical Note TN2271.

https://developer.apple.com/library/archive/technotes/tn2271/_index.html

The kAudioCodecBitRateControlMode constants are also defined in Apple's
public developer headers. Hope that’s useful!

— Charles