[iptv-users] Causes of jitter

[Frank Bulk]

Comments in-line.

Frank

-----Original Message-----
From: Dan White [mailto:dwhite at olp.net] 
Sent: Sunday, December 05, 2010 7:24 PM
To: Frank Bulk
Cc: iptv-users at puck.nether.net
Subject: Re: Causes of jitter

On 04/12/10 16:40 -0600, Frank Bulk wrote:
>One of our Calix rings is experiencing some very short video freezing (no
>perceptible interruption in the audio).  It appears to happen on all Calix
>nodes in that ring and appears to be regardless of channel.  Sometimes it's
>worse (almost unwatchable) and sometimes we get no complaints for days.
>Selective analysis of customer Calix ports counters show clean or very few
>errors, definitely nothing that I can attribute to physical plant.

What technology is it happening on? If ADSL, you might experiment with your
latency depth, assuming that the jitter was due to some problem on
the local loop.

FB> ADSL2+ and VDSL2.  We have the same latency depth on other networks, 
so I highly doubt that that's the problem.

>I watched one hour of programming Friday morning at a customer and counted
>15 freezing events, all of them but one very short.  We don't have any
>formal testing gear (yet), but a borrowed JDSU T-Berd is showing occasional
>jitter (up to 18 msec, sometimes 5 msec) and both the T-Berd and TS-Reader
>are showing identical Continuity Counter counter values.

You might ask your middleware vendor to check or verify the jitter buffer
size on your STBs.
FB> I asked our middleware vendor and she said "what's a buffer".

>Sometimes the freezing is accompanied by the CC going up by two (one for
>audio, one for video), other times the freezing doesn't have any change to
>CC, and sometimes the CC goes up and we don't perceive any freezing.
>
>I would like any and all input on:
>a) possible sources of the freezing

Other possibilities of freezing might be due to DHCP lease change or IGMP
timeouts.

FB> Not DHCP leases, but could be IGMP timeouts.  Hopefully the JDSU 
T-Berd would be telling us that.  

We've also seen encoder settings, and HDMI incompatibility (you might
verify it's happening on component) cause random freezes.

FB> Not an issue in other rings, so can't be encoder settings, and we
use this STB on other rings with all kinds of TVs, so can't be HDMI
compatibility.  Remember, other networks are fine.
-- 
Dan White