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@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@zz.de Professionell gesehen bin ich zu haben ....
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-- Denis Lackovic