[opendtv] Re: tolerance Latency , Jitters & packet loss issues for MPEG-2 TS over IP netwo

  • From: Prashant Desai <prashant.desai@xxxxxxxxxx>
  • To: opendtv@xxxxxxxxxxxxx
  • Date: Sun, 27 Feb 2005 00:29:40 +0530

kon

 anything wrong with the doubts that I had posted ......might be some of
then would be less relevant but then
the only objective of posting it was to understand the things clearly and
identify the better options by which things can be handled and nothing else
........since it's always not possible to get all the correct answers from
all vendors specially since its a very new area which is still not fully
implemented nor its fully evolved ....atleast not in this part of the world
.........anyway do let me know if have posted anything wrong or something
that's completely irrelevant .........if there are anything then I do
apologies for the same.

regards,
Prashant
----- Original Message ----- 
From: "Kon Wilms" <kon@xxxxxxxxxxxx>
To: <opendtv@xxxxxxxxxxxxx>; <opendtv@xxxxxxxxxxxxx>
Sent: Saturday, February 26, 2005 11:35 PM
Subject: [opendtv] Re: tolerance Latency , Jitters & packet loss issues for
MPEG-2 TS over IP netwo


> > Packet loss is evil - any lost paclets show up either as lost video or
> > audio.  You can add FEC, but some SIP STBs are not going to have the
> > processing power to do FEC in software and there aren't any IP STBs
> > with hardware FEC support.  Some MPEG-4 system do really long time
> > jitter buffers and retry on lost multicast packets.
>
> FEC on IP is rather pointless unless you want to start modifying the IP
stack drivers. The
> packets get ditched at the TCP or UDP decode layer if the checksum doesn't
compute, so they
> aren't even present for the error correcting decoder to attempt to repair
them. The desired
> mode for IP is to do plain ECC using large blocks - so you can recover
complete packets. For
> this you need vandermonde matrix based ECC, LDPC ECC, or similar.
>
> As for jitter, it is/can be a problem for IP networks. We've had to do
jitter analysis on IP
> streams (MPEG2 over UDP, RTSP, etc.) many a time, even when using large
decoder buffers.
> Can you name a manufacturer that doesn't make use of a SmartBits or
similar testing system
> when testing IP video servers and receivers?
>
> BTW Ethereal has a rather nice jitter analysis module with some graphing
functions, and its
> free.
>
> > Your middleware vendor better have the answer to all of the questions
> > or you picked the wrong vendor...
>
> Indeed. I have a feeling OpenDTV is the middleware consultant. And
Integrator. I'd just like to
> know what project this is that everyone keeps working on for free - there
must be something
> someone knows that I don't. :-)
>
> Cheers
> Kon
>
>
>
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