A correctly configured AVAudioSession is needed on iOS to:
- allow the application to capture microphone audio (in some cases)
- avoid playback being silenced in silent mode
Without this, initializing AudioUnit for capture can fail on iOS >=17 (from my testing).
Since AVAudioSession has a lot of settings, in most cases its setup should be handled by the user/app.
However, just to have a basic default scenario covered, let's configure the bare minimum ourselves,
and allow anyone to disable that behaviour by setting configure-session=false on src/sink.
Part-of: <https://gitlab.freedesktop.org/gstreamer/gstreamer/-/merge_requests/7856>
Adds the `atenc` element capable of encoding AAC-LC audio, using the AudioToolbox framework.
It's able to encode up to 7.1 channel configurations.
Comes with basic knobs for rate control (bitrate for CBR, quality for VBR).
Support for more profiles (LD, HE-AAC) should be simple, but is not included here because of bugs
with parsing of the AudioSpecificConfig.
Part-of: <https://gitlab.freedesktop.org/gstreamer/gstreamer/-/merge_requests/6254>
osxaudio has a few helper methods potentially useful in atdec (or future atenc), like GStreamer -> CoreAudio
channel mapping. Doesn't make sense to duplicate them in applemedia, and atdec is the only audio-oriented
element there anyway.
Part-of: <https://gitlab.freedesktop.org/gstreamer/gstreamer/-/merge_requests/6223>
