Subject: [AVT] RTCP transmission interval for HDTV

From: Alejandro Cabrera Obed <[email-masked]>
Date: Wed, 21 Sep 2005 14:30:20 -0300

Dear people,
 Suppose I have a HDTV transmission (audio + video) at about 1 Gbps.......I
will use RTCP in order to send synchronization information and some TFRC's
feedback.
 I suppose I have bandwidth enough, of course.
 I ask you: is it OK if I take 5% of the session bandwidth for the control
traffic (RTCP) bandwith ??? What do you suggest to me ???
 Thanks a lot,
 Alejandro

--
Alejandro Cabrera Obed
[email-masked]
_______________________________________________
Audio/Video Transport Working Group
[email-masked]
https://www1.ietf.org/mailman/listinfo/avt

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From: Magnus Westerlund <[email-masked]>
Date: Thu, 22 Sep 2005 09:49:46 +0200

Hi,

With the bandwidths you have 5% is usually way to much RTCP. The 
governing factor is the minimum interval for RTCP and not the bandwidth. 
However even that number using the default alternative formula for the 
minimal interval will yield a high rate of RTCP packets. The minimum 
interval for a 1 GB will be 360/1000000 = 0.00036 seconds which thus 
allows around 2700 RTCP packets every second. The reasonable rate of 
RTCP is at least once every RTT as this is the limit for doing network 
adaptation well. Considering the high data rates one also needs to watch 
for wrap around of the RTCP fields, however they should not be an issue 
here.

Cheers

Magnus

Alejandro Cabrera Obed wrote:
> ------------------------------------------------------------------------
> 

-- 

Magnus Westerlund

Multimedia Technologies, Ericsson Research EAB/TVA/A
----------------------------------------------------------------------
Ericsson AB                | Phone +46 8 4048287
Torshamsgatan 23           | Fax   +46 8 7575550
S-164 80 Stockholm, Sweden | mailto: [email-masked]

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From: Mark Baugher <[email-masked]>
Date: Thu, 22 Sep 2005 06:25:04 -0700

hi,

On Sep 22, 2005, at 12:49 AM, Magnus Westerlund wrote:

> governing factor is the minimum interval for RTCP and not the  
> bandwidth. However even that number using the default alternative  
> formula for the minimal interval will yield a high rate of RTCP  
> packets. The minimum interval for a 1 GB will be 360/1000000 =  
> 0.00036 seconds which thus allows around 2700 RTCP packets every  
> second. The reasonable rate of RTCP is at least once every RTT as  
> this is the limit for doing network adaptation well.

That seems reasonable, but RFC 3550 does not state that does it?  It  
seems that 3550 can be naively interpreted to mean that the RTCP rate  
is set to 5% of session bandwidth.

Mark
> Considering the high data rates one also needs to watch for wrap  
> around of the RTCP fields, however they should not be an issue here.
>
> Cheers
>
> Magnus
>