qtdemux: Add support for (parsing) audible AAX files
Audible AAX files are mp4 containers with an encrypted AAC audio stream.
The structure is almost the same as an MP4A file, only the mp4a atom is replaced by a proprietary 'aavd' atom, containing a standard 'esds' extension atom and an 'adrm' atom which holds the key material required for decrypting the content.
This MR does not implement the decryption but leaves this to a separate element, like done for the standard "Common Encryption" scheme.
An example decryptor element is available here: https://github.com/StefanBruens/gst-aavddec
Edited by Sebastian Dröge