Re: [Ccrtp-devel] adapative jitter buffer example

[Michel de Boer]

Hi David,

I did not really study the code for jitter that you posted, but I am 
triggered by
the topic of this mail thread. Has there always been jitter handling in 
ccRTP or
is this just new functionality?

If it is new, I would like it if the functionality is optional, i.e. it 
can be enabled
or disabled. Currently I am handling the jitter myself in my application 
(just a
simple static jitter buffer).
In the future I might remove my own jitter buffer coding in favor of the 
ccRTP
jitter buffer stuff.

You refer to modifying your jitter handling algorithm based on received RTCP
jitter reports. I wonder how you will do that. The received RTCP jitter 
reports
only give you information on the jitter experienced at the far-end, so 
that is
the RTP stream you are sending out. I don't see how this can help you 
handling
the jitter you experience on the RTP stream you receive.

Regards,
Michel


David Sugar wrote:

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>
> This is a section of code I developed over the last two weekends while
> rewriting the Bayonne SIP driver code and working on the Troll server.
> It essentially attempts to implement an adaptive jitter buffer in the
> run method of a Symmetric RTP stack.  Basically, it waits for some
> "initial" packet(s) to arrive, absorbs them, and then backs off to an
> additional packet timing frame, before processing further input, one
> frame at a time, all the while maintaining a wall clock for streaming of
> outgoing data.  If there are dropped (or silence suppressed) inbound
> packets, and the input queue hence becomes empty again, it simply
> resynchronizes to the next arriving packet(s) all over again.
>
> Federico thinks it could be adapted to be more flexible in the way it
> handles jitter by offering a settable jitter timing window larger than
> one packet frame, or perhaps even to further modify it's behavior based
> on rtcp jitter reports.  I may look at that.  Having an example of a
> reference implementation for Jitter handling in ccrtp, at least in in
> the documentation, if not in an actual example app, I think also would
> be very useful.
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>
> ------------------------------------------------------------------------
>
> void RTPStream::run(void)
> {
>        size_t r, n;
>        size_t size = info.framesize;
>        unsigned char buf[size];
>        timeout_t timer;
>         bool first = true;
>         bool jitter;
>
>        setTimer(0);
>
>        for(;;)
>        {
>                incTimer(info.framing);
>                setCancel(cancelDeferred);
>                enter();
>                if(source)
>                {
>                        source->getBuffer(buf, size);
>                        putBuffer(buf, size);
>                        r = dispatchDataPacket();
>                }
>                leave();
>                setCancel(cancelImmediate);
>
>                 if(first)
>                 {
>                         while(isPendingData(0))
>                         {
>                                 setCancel(cancelDeferred);
>                         r = takeInDataPacket();
>                         if(r < 0)
>                                 break;
>
>                                 jitter = false;
>                                 first = false;
>
>                                 enter();
>                         n = getBuffer(buf, r);
>                         if(sink)
>                                 sink->putBuffer(buf, n);
>                         leave();
>                         setCancel(cancelImmediate);
>                         }
>                 }
>                 else if(jitter)
>                 {
>                         if(isPendingData(0))
>                         {
>                                 setCancel(cancelDeferred);
>                                 r = takeInDataPacket();
>                                 if(r < 0)
>                                         break;
>
>                                 enter();
>                                 n = getBuffer(buf, r);
>                                 if(sink)
>                                         sink->putBuffer(buf, n);
>                                 leave();
>                                 setCancel(cancelImmediate);
>                         }
>                         else
>                                 first = true;
>                 }
>                 else
>                         jitter = true;
>
>                timer = getTimer();
>
>                if(timer)
>                        Thread::sleep(timer);
>        }
> }
>  
>
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