Bit rate for MP4 audio tracks

[gino0631]

Bit rate for MP4 audio tracks

[JamesHeinrich]

Thank you for the detailed breakdown, and links to the Chromium example, that was helpful.
I've implemented it at ce4a159
Please feel free to suggest any changes or improvements, PRs (very) welcome.

[gino0631]

Thanks for the implementation, I am so glad the references were helpful!

It is difficult with PRs without knowing the code well enough. As for the improvements, I think you already had a function to read the sizes - quicktime_read_mp4_descr_length() is quite similar to quicktime_readESsize().

[JamesHeinrich]

Sometimes I don't know the code that well myself -- most of getID3 was written 20 years ago...

You're right, quicktime_read_mp4_descr_length is a better implementation, I have removed quicktime_readESsize.