On Thu, Sep 30, 2010 at 1:26 PM, Frederik Kriewitz <frederik@kriewitz.eu> wrote:
On Thu, Sep 30, 2010 at 10:15 AM, Denis Lackovic <denis.lackovic@iskon.hr> wrote:
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.
I prefer RTP retransmissions over FEC too. Especially because it's similar to RTP Bursts for rapid channel changing. I looked into this topic some time ago, for me cisco's VQE seems to be the way to.
RTP Retransmission specification: http://www.ietf.org/rfc/rfc4588.txt VQE-Client reference implementation: ftp://ftp-eng.cisco.com/ftp/vqec/
Rapid synchronization related specs (I'm not sure how it's implemented by VQE): http://tools.ietf.org/html/draft-ietf-avt-rapid-rtp-sync-12 http://tools.ietf.org/html/draft-versteeg-avt-rapid-synchronization-for-rtp-... http://tools.ietf.org/html/draft-ietf-avt-rapid-acquisition-for-rtp-15
Lately there are some other companies offering Cisco VQE based server side solutions (as the protocol itself is open).
Do you have some links for me? I couldn't find anything. Anyone knows about an open source VQE-Server implementation?
For example Edgeware (edgeware.tv) VQE implementation should be available next month. I'm waiting for a software upgrade to test it myself. They are well known as a VOD server vendor (high performance flash storage based unicast). I'm not aware of an open source VQE server implementation. -- Denis Lackovic