[Ffmpeg-devel] [PATCH] RTCP valid receiver statistics....

Michael Niedermayer michaelni
Wed Nov 1 00:59:15 CET 2006


Hi

On Tue, Oct 31, 2006 at 03:17:40PM -0600, Ryan Martell wrote:
[...]
> >[...]
> >>+#if 0
> >>+/**
> >>+* This function is currently unused; without a valid local ntp  
> >>time, I don't see how we could calculate the
> >>+* difference between the arrival and sent timestamp.  As a  
> >>result, the jitter and transit statistics values
> >>+* never change.  I left this in in case someone else can see a  
> >>way. (rdm)
> >
> >the system time should be used
> 
> really?  how do I get system time in 64 bits, without just taking  
> time_t and shifting appropriately? 

hmm i dont think there is a portable way (or at least iam not aware of one)
on x86 rdtsc could be used, there are probably also a few gnu extensions with
which you could get an accurate time though i dunno how accurate and all
that wouldnz help non gnu non x86 ...
iam not sure how important that jitter stuff is? getting an accurate 
time will likely be more complicated then i thought at first, rdtsc
would also require the ticks/sec to be known ...


> I don't know what the server does  
> with the jitter, but i would be afraid of screwing something up if  
> the two machine's times aren't close.

the jitter calculation in rfc1889:
D(i,j)=(Rj-Ri)-(Sj-Si)=(Rj-Sj)-(Ri-Si)
J=J+(|D(i-1,i)|-J)/16

is invariant under adding a constant to either the source or destination
time, so it doesnt matter if one is of by an hour or 5000 years
but of course accuracy matters ...


[...]
> >[...]
> >>+#if defined(DEBUG) && 0
> >>-#if defined(DEBUG) || 1
> >
> >unrelated change?
> 
> Nope; I am replacing the old method of checking sequences with the  
> new method.
> 
> This version of the patch strips it out. (and fixes the above, except  
> system time, which I would like to put in a later patch to setup the  
> jitter).

ok and patch looks ok

[...]
-- 
Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

In the past you could go to a library and read, borrow or copy any book
Today you'd get arrested for mere telling someone where the library is




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