Greetings, new to Linphone and new to the list. We've been testing the AAC-ELD implementation, which I was very surprised and happy to find. We see that the call used by MediaStreamer2 is "kAudioFormatMPEG4AAC_ELD". This is actually only using half of the capabilities of ELD, the other half being Spectral Bandwidth replication, which allows it to sound much better at low data rates. Was this intentional? Industry standard AAC-ELD implementations (like used for broadcasting) all include SBR (It's kind of the point of ELD).
The call to run the codec with SBR would be "kAudioFormatMPEG4AAC_ELD_SBR"
Also, where did the choice of bitrates come from? To be compatible with most other implementations 48KHz would be the choice.