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WooshCom has devised a filter designed to make MPEG traffic on HFC networks much more bandwidth-efficient.

The company's MPA-1212 filter strips out MPEG Null packets being forwarded onto ASI interconnects within a headend by satellite receivers.

"Typical numbers we are seeing are a 4 Mbps standard-definition video stream being embedded in a 54 Mbps torrent of data, but on some receivers, this deluge is as high as 155 Mbps. It is like trying to drink from a fire hydrant," said Bruce Marler, WooshCom's CTO and founder.

If the MPEG stream from SPTS receivers is immediately converted to IP data and is fed onto an LAN or a fiber network, the UDP/IP packets from that point on can permanently clog up the network. Ultimately that can artificially inflate fiber link capacity requirements, WooshCom explained. If the fiber is being leased, the operator may be buying more capacity than necessary.

In a typical cable TV headend, the stream is sent straight to a modulator, to an MPEG-2 remultiplexer or onto an IP data network perhaps for fiber distribution. Today's generation of MPEG headend equipment is CPU-based, and hence they cannot distinguish between an MPEG Null packet and an MPEG Information packet without executing those software routines designed to do that.

"This needlessly consumes CPU processing power on these expensive devices, taking that power away from the more significant functions that the devices were purchased to perform like multiplexing, rate shaping or rate capping," Marler said.

Some remultiplexers and transcoders have limits on their ingest rates in the 450 to 600 Mbps range that cannot be exceeded without bringing down the services.

"While this may sound like a large number, it is quickly exceeded if it is fed by SD video streams, each of which is embedded in 54 Mbps. Just nine to 11 such feeds will cause these ingest rates to be exceeded and customer services to be interrupted," said Marler.

The MPA-1212 is DVB-ASI based with one input, one loop-thru output and two mirrored filtered outputs, and hence additionally performs the function of an ASI distribution amplifier.

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