Posted on: Sep 04, 2018
Posted by Doug Engstrom
The new QMODs have the ability to output the video stream as an RF channel, an IPTV stream, or both at the same time.
First, it may surprise you that a digital QAM channel has always been an MPEG2 video stream. The only difference from Video over Ethernet is that the stream is carried by over RF instead of IP. So when we create the MPEG2 stream, it;s automatically compatible with RF and IP. We just have to add data to the stream when you opt for Ethernet to allow Unicast or Multicast network operation.
What Are the Streaming Options?
Presently, the IPTV stream is essentially the same as the RF Transport Stream.
- If the QMOD is set to provide only one program (no video input assigned to Program B), the IPTV stream will be an MPEG2 single program transport stream (SPTS), either for multicast or unicast.
- f the QMOD is set to use two programs, the IPTV stream will be an MPEG2 multiple program transport stream (MPTS), either for Multicast or Unicast.
- There isn’t a way to create one MPTS stream for RF QAM, and also create two SPTS streams for IP. That would require 4 encoders.
To Stream or Not to Stream
Presently, we are broadcasting the same stream for RF and IPTV. That’s a full-bore HD MPEG2 stream typically set to 18 Mpbs for a single-program stream, 38 Mbps for a dual-program stream. Common for RF, a really big stream for many networks. This can be reduced by lowering the bitrate on one or both channels.
If the QMOD is set for Ethernet only, you can set the QMOD to variable bitrate, which will reduce bandwith for typical content.
When the QMOD is set for dual-channel operation, not all IPTV recievers can be set to recieve 2 programs in one stream. Better IPTV receivers can, likely not for inexpensibe recievers such as Amino.
We are also working on adding MPEG4 encoding, which isn’t univerally tunable over RF, but much more efficient for network applications.
In summary, the IPTV stream we produce now may not be usable for sites that have restricted bandwidth. However, we already have next-gen beta QMODs delivering ITPV streams in several installations, so there are valid applications today.
While IT manager’s networks may not have the bandwidth for for truly HD MPEG2 streams, they appreciate that QMOD’s applications don’t end with RF, but will support MPEG4 streaming in the future. Many also like the ability to broadcast media over RF, giving them a pathway for facility-wide media that won’t stress their current network.
This form of Video over Ethernet creates a link from the QMOD to a specific IP reciever. The pros are that this stream will operate over most current networks and routers. The takeback is that you can only stream to one receiver at a time, and you need to set up the link within the QMOD.
Muticasting is far easier to implement, as you just broadcast the stream with a multicast address, and the routers do the work of sending the stream to receivers that request it.
The usual catch for integration is that not all routers can handle multicasting. All the site’s routers must have multicasting enabled, with requires either software updates or new routers. Of the beta sites where QMOD IPTV technology is used, we are doing multicasting over 1G networks. In addition, the routers are set up as a VLAN, separating the media streams from the standard traffic.
Multicast IP addresses range from 184.108.40.206 through 220.127.116.11, which are set aside for multicast streams. However, there are “reserved” combinations in that range that don’t work efficiently, so you’ll want to use addresses assigned by the IT department. Typical “non-reserved” addresses include:
Return to blog