FEC for getstream

[Denis Lackovic]

In the world of telco grade IPTV installations error correction is
done when you have a bad copper pais in your ADSL network.
There are 2 ways to do an error correction on a multicast udp/rtp:


1. FEC - you have product from Bitband - additional multicast FEC
stream  is createad alongside original multicast tv channel stream.
STB joins to both streams and when an error occurs on a channel
multicast stream it tries to reconstruct missing packets using FEC
data. This requires a client on a STB.

http://www.bitband.com/general_cat.aspx?CatID=18

This solution is not widely used as it requires more bandwidth than
second solution (Cisco VQE aproach).

2. Unicast retransmission of missing packets - Cisco VQE is most
popular solution for error correction in the IPTV world.
They have many installations around the world.
 This solution also requires Cisco VQE client on the STB - it is open
source (Cisco sells server side equipment).

This solution requires tv channels to use multicast UDP/RTP. When a
packet is found missing on an STB, VQE client request a retransmission
of a packet from VQE server - it knows exactly which packets are
missing as it uses RTP sequence numbering.

Server sends back required data using  unicast. This requires
additional bandwidth on top of the tv channel bandwidth, but only at
the time of retransmission.

Lately there are some other companies offering Cisco VQE based server
side solutions (as the protocol itself is open).





-- 
Denis Lackovic



On Thu, Sep 30, 2010 at 9:48 AM, Florian Lohoff <f at zz.de> wrote:
>
> Hi,
>
> i was thinking about FEC (Forward Error Correction) as thats what i heard
> people use in WAN IPTV Products to protect against low probability
> ip packet loss.
>
> Does anyone of you use something like this today? Does anyone have a client
> which supports something like this (would need testing) and at which level
> do you add FEC?
>
> Flo
> --
> Florian Lohoff                                                 f at zz.de
>                 Professionell gesehen bin ich zu haben ....
>
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-- 
Denis Lackovic