Dear Jacques,
On 10/25/2012 11:17 AM, Jacques Tiete wrote:
Hello Magnus,
I know what you're talking about, I'm working for a company specialized in
broadcasting (from studio's to stations to satellites...) and in this
world correct
timing is paramount, we live by the 1/25 second rythm and even less if you
have to sync on a line in the image ;-).
Some time ago we were instaling a complete TV station and had huge problems
with image stability and also especially the correct starting time of a
clip or transmission.
Nobody wants to start his newsreel at eg. 20:00:05;23... it must be
20:00:00;00
We were looking into this and noticed that the customers servers (Win!)
where
synced by SNTP, this is plain c..p!
Have a look @
http://technet.microsoft.com/en-us/library/cc773013(WS.10).aspx
Especially where it says:
*/"Important
The W32Time service is not a full-featured NTP solution that meets
time-sensitive /*
*/application needs and is NOT SUPPORTED by Microsoft as such. For more
information, /*
*/see Microsoft Knowledge Base article 939322, Support boundary to
configure the /*
*/Windows Time service for high-accuracy environments."/*
Also have a look @ http://support.microsoft.com/kb/939322
It says:
*/"We do not guarantee and we do not support the accuracy of the W32Time
service /*
*/between nodes on a network. The W32Time service is not a full-featured
NTP solution/*
*/that meets time-sensitive application needs. The W32Time service is
primarily /*
*/designed to do the following:/*
*/Make the Kerberos version 5 authentication protocol work.
Provide loose sync time for client computers.
The W32Time service cannot reliably maintain sync time to the range of 1
to 2 seconds. /*
*/Such tolerances are outside the design specification of the W32Time
service."/*
So it is... 1 to 2 seconds....!!!!!!!!
These are very valuable references, many thanks for bringing them to my
attention.
Our video playout servers are decent super stable units that use heaps
of Xilinx FPGA's
for coding/decoding videostreams supervised by a mil-spec VXworks OS, it
uses the
so-called LTC for synchronising the playout, implemented mostly in
hardware so
I did not suspect our machines. I did install a new TCG (TimeCode
Generator) where
I also had heaps of problems with, I did debug the stuff together with
the manufacturer's
R&D and finally got a perfectly synced station AND a Stratum-1 NTP
(everything in
double with automatic failover, a requirement for a TV-station). (Thanks
to lurking for
years as a genetically predispositioned Time-Nut, my father was a
watchmaker...So I
knew more or less what a was talking about and could prove things thanks
to my TBolt etc.)
Then I did install Meinberg NTP-client on every Win machine and all was
suddenly
perfectly running, everybody happy!
This also solved some frequent file versioning problems for storing
different versions of
videoclips especially in a mixed Win/Lin environment where Linux proved
to be the
more logical/strict way of implementation.
This is a valuable experience to share. Many thanks!
Another thing, being considered as the local video timenut a colleague
called me from
Saudi Arabia where he was having timing problems on two locations spaced
700km. apart
where he had funny image jumps at the exact same time, both stations
were synced by
each the same TCG with GPS option (same as above), could the americans
jam the GPS
signals over there, somebody heard about this? It could be a real
problem for us, we
may need to use another method for station timing (Rb maybe, with some
regular syncing
etc.)
There are geographical areas where you have higher risk of being the
indirect target, yes.
Sorry for my long message but I don't often send timenut mail and this
is a good example
of some real-life timenutting ;-)
Then you should share me of your experience. :) This was a very nice post.
I also have here a nice BeagleBone mini Linux board resting, where I
would want to install
a FreeBSD image on and implement a NTP with a promising GPS board from
Adafruit,
something for the long and cosy winter evenings... :-)
So many nice projects. :)
Have a BeagleBone lying around here somewhere. Putting a GPS onto it
would be a great project. :)
Cheers,
Magnus
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