[Freeswitch-users] RTP timestamps jumping backwards

Richard Brady rnbrady at gmail.com
Fri Mar 28 15:39:09 MSK 2014


Thanks Peter

That's really useful. I opted for rtp-rewrite-timestamps but had missed
that one and will try it next if I don't see an improvement. There's also
RTP_BUG_SEND_LINEAR_TIMESTAMPS.

I'm quite confident I can work around the issue but would like to make sure
that if there is an RFC non-compliance in default FS we get it resolved for
the benefit of others.

My understanding:

The marker bit makes it ok to jump the timestamp for silence suppression /
discontinuous transmission etc.

BUT the marker bit doesn't make it ok to change the timestamp SOURCE (and
jump the timestamp backwards for example). In that case the SSRC MUST
change too.

Regards,
Richard

On 28 March 2014 11:08, Peter Olsson <peter at olssononline.se> wrote:

> There is actually a setting to force new SSRC in a condition like that.
>
> Internally it's called RTP_BUG_CHANGE_SSRC_ON_MARKER. If I remember
> correctly it should be set in the sofia profile config:
>
> <param name="auto-rtp-bugs" data="CHANGE_SSRC_ON_MARKER"/>
>
> Try that out and see if it helps.
>
> /Peter
>
>
> 2014-03-28 11:37 GMT+01:00 Richard Brady <rnbrady at gmail.com>:
>
>> Hi Anthony and team
>>
>> I have a situation where the timestamp in a RTP stream generated by FS
>> jumps backwards. Version 1.2.22.
>>
>> It seems the cause of this is that media from the A leg starts late. So
>> in the meantime we start generating media on the B leg with our own
>> timestamp.
>>
>> Then media starts arriving on the A leg so we relay it and we start using
>> that timestamp instead of our own.
>>
>> FS sets the marker bit when this happens but I'm not sure this makes it
>> OK to turn back the timestamp. I think we should actually be using a new
>> SSRC.
>>
>> Any thoughts? (happy to raise a Jira ticket and verify in master).
>>
>> Richard
>>
>> --
>> Richard Brady
>> M: +44 (0)7771 623 348
>> T:  +44 (0)20 8144 8160
>> E: rnbrady at gmail.com
>>
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