[Live-devel] normalization of frame presentation time in live555ProxyServer

[Massimo Perrone]

Hello Ross, thanks for the response,

I see, the values of NTP time and rtp timestamp in the RTCP SR packet 
are based on the wall clock time of the RTSP proxy, so they don't depend 
on the (synced) presentation time of the incoming frame.

Just to know if I am understanding correctly the issue: could we have 
the same effect by not synchronizing the source on the reception of a 
RTCP SR ? At that point the presentation time of all the incoming frame 
would be automatically synchronized with the proxy wall clock time, and 
the RTSP proxy could eveb send an initial SR (as it does by default).

Thanks again,

Massimo Perrone


On 25/01/2019 18:31, Ross Finlayson wrote:
>> I cannot exactly understand what is the purpose of the PresentationTimeSessionNormalizer used in live555ProxyServer.
> The issue here was that our RTSP *server* implementation (code) depends on the presentation times for outgoing frames (transmitted by the server) being aligned with the server's ‘wall clock’ time (in order for the server’s outgoing RTCP “Sender Reports” to be correct).
>
> Therefore, when our ‘server’ is actually a proxy server (which takes its input from some other, ‘back-end’ server, not necessarily implemented by us), we can’t just use the presentation times that came from the ‘back-end’ server ‘as is’.  Instead, we need to adjust them so that they’re aligned with the proxy server’s ‘wall clock’ time.  That’s what “PresentationTimeSessionNormalizer” (and “PresentationTimeSubsessionNormalizer”) does.
>
> Ross Finlayson
> Live Networks, Inc.
> http://www.live555.com/
>
>
> _______________________________________________
> live-devel mailing list
> live-devel at lists.live555.com
> http://lists.live555.com/mailman/listinfo/live-devel