[Linphone-developers] Linphone, Opus and the current RTP draft

[Fredrik Bergholtz]

Hi. I am very new to this code-base. In fact it took me many hours to even get it to compile on my brand new MacBook.

The first reason for me to get involved at all is that the current draft of the Opus RTP packaging RFC (http://tools.ietf.org/html/draft-ietf-payload-rtp-opus-01) states that the rtpmap line of the SDP MUST always state a 48000 rate and 2 channels regardless of actual sample rate or channel count.

Has there already been a discussion on this topic and a fix on the way or should I try to dig into the code?

I made a feeble initial attempt to just change the default value in ms_opus_enc_init() but since that didn't help, I assume that the iPhone app explicitly sets the number of channels somewhere and that this changes both the "stereo" fmtp parameter AND the rtpmap channel count. So far I have not yet managed to figure out where and how this happens and what other problems might occur when de-coupling(?) the channel count of the rtpmap and the actual encoder/decoder.

Any thoughts?

Best regards
Fredrik