[SR-Users] RTPEngine / Transcoding question

[Richard Fuchs]

On 29/05/2019 03.25, Carsten Bock wrote:
> Hi,
>
> the problem is, the device (a VoLTE phone) will ALWAYS offer AMR-WB 
> and AMR-NB and we will need to do transcoding to G722 / G711 in most 
> cases (unless the B-Party actually offers AMR-WB/AMR-NB).
> The Answer may be pure G711 (RTPEngine will do Transcoding G711 <=> 
> AMR-WB [meaningless]) or G722 (RTPEngine will do Transcoding G722 <=> 
> AMR-WB [Makes sense]) or AMR-NB/-WB (no Transcoding [ideal]). If I 
> could limit the Answer from RTPEngine to contain only AMR-NB, that 
> would ideal, as AMR-NB has less complexity, than transcoding into 
> AMR-WB and it would additionally save bandwidth (which is important in 
> our case).

Ah I see. As explained already, making this decision at the time the 
answer comes through doesn't really work, because the codec in question 
might already be in use at that time. What you would like to see instead 
is to make a decision at the time of the offer: Transcode one of the 
offered transcoded codecs to a particular one of the original offered 
codecs ("offer G.722 and transcode to AMR-WB"), and transcode another 
offered transcoded codec to another one of the original offered codecs 
("offer G.711 and transcode to AMR-NB"). Something along those lines, 
correct? That's simply a feature that doesn't yet exist, as right now 
transcoding always happens to the first supported original codec (i.e. 
if AMR-WB is first in the list, then that's what will be used).

Cheers