Is HE-AAC (v1 and v2)
_encoding_
possible on iOS?
Judging from this link
https://developer.apple.com/library/content/documentation/AudioVideo/Conceptual/MultimediaPG/UsingAudio/UsingAudio.html
where HE-AAC is mentioned only in the decoding table it would seem
that encoding isn't supported.
OTOH, judging from the comment at this link
https://developer.apple.com/reference/audiotoolbox/1559928-audio_converter_properties/kaudioconverterpropertyformatlist?language=objc
even v2 should be supported...
Finally, modifying the ExtendedAudioFileConvertTest example/demo
source code to produce HE-AAC v1 files
_works_ but
_does
not work_ if I try v2
(with "Couldn't set the client format on the destination
file!")...