normalization of frame presentation time in live555ProxyServer

[Massimo Perrone]

Hi all,

I cannot exactly understand what is the purpose of the 
PresentationTimeSessionNormalizer used in live555ProxyServer.

As far as I can see, the presentation time of the incoming frames are 
adjusted (as long as they have been synced with a RTCP Sender Report) by 
adding an offset, which is computed at the beginning as the difference 
from the current presentation time (fromPT) and the local wall clock 
time (timeNow). Once this adjustment is done, the sending of RTCP Sender 
Report on the downstream RTP sink is enabled.

But the NTP timestamp contained in a RTCP Sender Report packet is anyway 
constructed from a wall clock time, via gettimeofday(), so its contents 
does not depend on the actual frame presentation time. On the other 
hand, the RTP timestamp in each RTP  packet, even if computed starting 
from the frame presentation time, is relative, so it should not depend 
on  any adjustment.

May be there is something missing in the picture...

Thanks in advance,

Massimo