Re: [rtcweb] JSEP: Issues with a=ssrc and RTP payload type switching

[Simon Perreault <[e-mail]>]

Le 2015-06-08 03:36, Magnus Westerlund a écrit :
> Harald Alvestrand skrev den 2015-06-08 11:19:
>> Den 08. juni 2015 10:48, skrev Magnus Westerlund:
> 
>>> However, this can't work as RFC 7160 says in Section 4.1:
>>>
>>>    An RTP Sender with RTCP turned on MUST use a different SSRC for each
>>>     different clock rate.  An RTCP BYE MUST be sent and a new SSRC MUST
>>>     be used if the clock rate switches back to a value already seen in
>>>     the RTP stream.
>>>
>>> Note the second sentence. One would still have to do a new round of
>>> signalling to prime a new SSRC for the previous rate after having
>>> switched to be able to switch back to that Payload Type.
>>
>> Hm. I missed that when reviewing the clock-rate doc.
>> So that means one uses up an SSRC for every clock rate switch. That
>> seems silly; is it possible that this should be considered an erratum
>> for RFC 7160?
> 
> No, it is highly intentional as I remember the discussion.

Can you please explain, for those of us with short memories? :)

>> Are there legacy gateways that will NOT fall over on a clock rate + SSRC
>> switch?
> 
> Good Question!

Depends what you mean by "legacy". My gateway will not fall over.

>> If so - what do these legacy gateways do when switching back to the
>> original PT? New SSRC, or back to a previously used SSRC?

As RFC 7160 says: new SSRC.

Simon