[asterisk-users] Change Asterisk MulticastRTP codec

[Larry Moore]

On my Asterisk 11 system I have the following in extensions.ael for 
chan_sip.

         8001    => {
                 Set(SIP_CODEC=alaw);
//Dial(MulticastRTP/linksys/224.168.168.168:34567/224.168.168.168:6061);
Page(MulticastRTP/linksys/224.168.168.168:34567/224.168.168.168:6061,q,5);
                 Hangup();
         };


I believe in your case you need to set PJSIP_MEDIA_OFFER(ulaw) in a 
pre-dial handler prior to making the call.

See 
https://wiki.asterisk.org/wiki/display/AST/Pre-dial+handlers+Specification.




On 1/10/2015 1:51 AM, Matthew Murphy wrote:
> Greetings everyone,
>
> I was wondering if there was a way to change the codec that Asterisk 
> uses when streaming via MulticastRTP. Or perhaps a way to transcode 
> the multicast stream.
>
> In the CLI, when I have a multicast stream in progress, I am typing 
> 'core show channel MulticastRTP/0x7f7........' to get lots of helpful 
> information.
>
> I have noticed that when I do a MULTICAST page and* send data from 
> MP3Player*, I get no sound on my speakers and get the following from 
> 'core show channel PJSIP/xxx':
>
> NativeFormats: (slin)
> WriteFormat: slin
> ReadFormat: slin
> *WriteTranscode: No *
> *ReadTranscode: No *
>
> I have noticed that when I do a UNICAST page and* send data from 
> MP3Player*, everything works flawlessly and I get the following from 
> 'core show channel MulticastRTP':
>
> NativeFormats: (ulaw)
> WriteFormat: slin
> ReadFormat: slin
> *WriteTranscode: Yes (slin at 8000)->(ulaw at 8000)*
> *ReadTranscode: Yes (ulaw at 8000)->(slin at 8000)*
>
>
> The *only* thing that is changing is the following line in my 
> extensions.conf file:
>
> ; For Multicast Paging
> same => n(next),Page(MulticastRTP/basic/239.1.1.2:6061,q)
>
> ; For Unicast Paging
> same => 
> n(next),Page(PJSIP/107&PJSIP/108,ib(pjsip-auto-answer-header^addheader^1)|p})
>
>
> Is there any way to get the MP3Player stream to transcode (as it does 
> on the UNICAST stream) when I try to MULTICAST?
>
> Thanks for the help,
>
> --Matt
>
>

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