Re: [Linphone-developers] Using oRTP to send supplemental data besides the audio

[Vadim Lebedev]

Steve Strobel wrote:
> I am using oRTP to send G.711u audio between some embedded devices 
> that use Blackfin processors;  that is working very well.  There is a 
> small amount of other data (status information only loosely related to 
> the audio) that I also need to pass between those embedded devices.  I 
> can think of at least three options for doing that (listed from 
> least-to-most preferable):
>
> - Open another socket directly from the application code and use it to 
> send the status information.  I would then have to manually deal with 
> STUN and other firewall/NAT issues that oRTP already takes care of.
>
> - Create a separate RTP session for the data, sending it like audio 
> data, but with a different payload type.  The data isn't a continuous 
> stream, so this seems like a kludge.
>
> - Send the data using the same RTP session as the audio.  This seems 
> to me like the cleanest method, but I am not sure of the best way to 
> accomplish it.
>
> Reading through the API documentation at 
> <http://savannah.inetbridge.net/linphone/ortp/docs/> three 
> possibilities jumped out at me:  telephone events (such as those used 
> to send DTMF digits), FMTP, and RTCP.  Is one of those well suited for 
> my task, or am I completely on the wrong track?  Thanks for any 
> suggestions.
>
>
> Steve
>
>
>
> ---
Hi Steve,

IMO it depends on the amount of additional data you want to send:
If it  3-4 bytes each time i'd use existing rtp session and would send 
it as DTMFs
Otherwise i would create a separate session, with jitter buffer 
deactivated and using 16 PCM as payload type.
You however need to be aware that in this case the data could be lost.

Thanks
Vadim