[Live-devel] fJitter may be wrong?

[Fangweiwei]

Ross Finlayson,hi£¡

	I don't know why RFC 3550 computes it as that.

    Now I do some work as Network Emulation. And when I changed the virtual network, from good to bad (eg.packet loss), I calculate the packet jitter using standard deviation fomula.and It reflects that the network quality. If packet loss too much, the packet jitter will become big...

    but unfortunately, I find the fJitter changes slightly.I don't know why?

    Thank you very much for all your answer! 

======= 2004-10-22 04:44:00 You Wrote in your letter£º=======

>
>>           As I know, Jitter is standard deviation of inter-packet time
>
>Not quite.  In the RTP specification (RFC 3550, section 6.4.1), the 
>"interarrival jitter" is defined as
>         "An estimate of the statistical variance of the RTP data packet
>       interarrival time, measured in timestamp units and expressed as an
>       unsigned integer.  The interarrival jitter J is defined to be the
>       mean deviation (smoothed absolute value) of the difference D in
>       packet spacing at the receiver compared to the sender for a pair
>       of packets."
>
>>but As in the RTPSource.cpp:
>>
>>       fJitter += (1.0/16.0) * ((double)d - fJitter);
>>
>>       May be it is wrong??
>
>No, because this is the same formula given in section 6.4.1 and Appendix 
>A.8 of RFC 3550.
>
>
>	Ross Finlayson
>	LIVE.COM
>	<http://www.live.com/>
>
>_______________________________________________
>live-devel mailing list
>live-devel at lists.live.com
>http://lists.live.com/mailman/listinfo/live-devel
>

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¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡Yours Sincerely
 
				 
¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡Fangweiwei
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¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡2004-10-22