Re: [AVT] Fwd: I-D Action:draft-perkins-avt-rapid-rtp-sync-03.txt

[Randell Jesup <rjesup at wgate.com>]

Stefan Döhla <stefan.doehla at iis.fraunhofer.de> writes:
>>> Then I think my assumption was correct, that you need to pre-filter the
>>> NTP timestamps so that they increase roughly linearly - but at least
>>> monotonically with each according RTP timestamp - otherwise it would be
>>> possible to align samples from several layers but it is no more
>>> guaranteed that they have the timestamps in correct order).
>>
>> I need an example to follow you here :-)
>
>The example would be related to the bad behaviour of some implementations
>that create quite rough RTCP SRs when it comes to timestamp creation. I
>think Asterisk was a good example of NTP timestamps that jump back and
>forth. If the same bad clock would be used to write the NTP timestamp for
>the HDR_EXT, then you would end up with subsequent packets where the RTP
>timestamp is e.g. monotonically increasing but the NTP timestamp is not
>because there's a high jitter added.

"jumping around" doesn't even come close to describing what Asterisk does
to RTCP timestamps.  "Virtually random" is closer, or "totally useless".

Sorry, sore point. 1/2 :-)

-- 
Randell Jesup, Worldgate (developers of the Ojo videophone), ex-Amiga OS team
rjesup at wgate.com
"The fetters imposed on liberty at home have ever been forged out of the weapons
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