Interconnecting IPTV

It takes planning to encode, brand, multiplex and transmit at multiple sites

The project that has occupied the vast majority of our time over the last few months is what we have called our "interconnect project." The Iowa Public TV network of transmitters are all connected back to the studios in Johnston via fiber -- optic DS -- 3 circuits. The Iowa Communications Network (ICN) is the Iowa state agency that owns and manages the state's fiber network and we use it for transport services to and from our sites. Each transmitter facility has a dedicated DS-3 that allows us to send unique programming to each transmitter if we desire.

We seldom use this capability since we produce very few pieces of content that are of interest to only a specific area of the state. However, as we have planned for the DTV conversion, we have begun to explore utilizing this capability more-not so much for programming, as our mission is to produce content for all Iowans, but for other services such as datacasting and providing media -- rich content to K -- 12 schools. We believe that by managing how and where ancillary services like datacasting are processed and delivered we can provide a relatively high capacity and rapid delivery service while still serving the IPTV viewing audience with high-quality content.


We began the process by doing some serious research and visiting a lot of end users and manufacturers to see what they were doing. The result of the research was a request for proposal (RFP) that was submitted to the State of Iowa General Services for release. Unfortunately, due to some miscommunications, the RFP was processed and released as a straight bid request. I won't go into all of the details of the differences between the bid and RFP process, but suffice it to say that the primary difference is that in a bid, low price wins and in an RFP the best solution wins.

Conceptually, what we were looking for is a system that would allow IPTV to encode HD and multiple channels of SD content, brand those content streams, multiplex them with ancillary data and content and then send the complete package to a multiplexer that combines the 19.39 Mbps stream with a digitized analog program stream to be sent over DS-3 to our transmitter sites.

The proposed setup for the transmitter sites consists of a de-multiplexer and the hardware necessary to convert the analog transmitter's program stream back to video and audio for NTSC broadcast, plus the hardware to supply the transport stream to the ATSC transmitter for broadcast.

We configured the monitoring and return feed systems to create a facility for passing through PBS digital content and mix it with our own locally generated digital content and send it over the existing DS-3 lines without increasing our bandwidth requirements because even though the State of Iowa owns the ICN, we're still required to pay that agency for the bandwidth that we use. We also wanted the DTV broadcast to look good, and because we had no budget for any significant master control build-out, we wanted to incorporate the basic MCR functions in the interconnect package.


As you can tell, this is a fairly aggressive and comprehensive system, and while the bid process was open we fielded a number of questions and went through a lot of addendums and clarifications. One reason for going with the RFP process was that we had from our observations come up with a basic concept but we were very interested in evaluating alternative ideas and methodologies for any or all parts of this process. In truth, we did get a number of interesting ideas and suggestions for this project and would love to incorporate some of them into the project. Unfortunately, most of them require a significant alteration that materially change the bid and invalidate the process.

Obviously one of the most significant components in this system is the encoder for HD and multiple channels of SD. Probably as a single system component, it is the most expensive. Our bidders were all over the place on hardware selection and encoders from Harris, Harmonic and Tandberg were all proposed. One of the evaluation criteria that has become important to us, interestingly enough, is the performance of the encoder when encoding at low data rates.

This has become a priority because, as mentioned above, some of our potential clients for ancillary services are K-12 schools. The State of Iowa has a number of regional media centers located throughout the state; each acts as a library for K-12 schools in its region for specialized classroom content including instructional videos. These videos are typically VHS cassettes that teachers order and wait a week or more for.

We see a great potential for offering an overnight delivery of this content using DTV as the transport medium and something as simple as a TiVo or PC with a tuner card as the receive device. Since the original content master is VHS resolution, encoding that material at relatively low rates would allow us to deliver multiple content streams to multiple locations with little impact to our DTV broadcast, even when doing HD or multicast.

Unfortunately, our experience shows that the coding algorithms tend to fall apart when running at low rates, and this is not something that we have tested with anything other than a demo Tandberg E5820 that we purchased from a vendor. So as odd as it sounds, we're now evaluating how well encoders handle HD, SD and something less than SD at various data rates.


A final monkey wrench in the process that will ultimately be a tremendous benefit to our operation is the recent revelation from PBS of a technology initiative that has the potential to completely alter our station's concept and implementation of master control in DTV. The concept is to centralize traffic and log functions and roll out to the stations an edge device that they can control locally for local program or run fully automated for normal operations while maintaining the same flexibility in scheduling.

Part of this package is the encoders needed for DTV broadcasting. I have recently been named to a team of station engineers that is working closely with PBS on the design, testing and implementation of this concept. The concept is so appealing to us that we have volunteered to be in the first group of stations that will roll out this technology.

Unfortunately we're talking about a system that will probably not be ready for station implementation until the middle of 2004 and we are still tasked with getting on the air. Our plan now would be to implement some very limited DTV capabilities by using the current Tandberg encoder we have and feeding that out via the interconnect to the other stations. The problem is that this will certainly be seen as a material change to the bid documents and will lead us to redoing the RFP to incorporate just the basic interconnect, multiplexing, monitoring and control portion of the package. I am generally not a big fan of "do-overs" but given the potential long-term benefits that we see to our operation, the opportunity is too important to miss. I suspect I will be writing a number of Digital Journals on this subject.

Bill Hayes

Bill Hayes, director of engineering and technology for Iowa PBS, has been at the forefront of broadcast TV technology for 40 years, 23 of them at Iowa PBS. He’s served as president of IEEE’s Broadcast Technology Society, is a Partnership Board Member of the International Broadcasting Convention (IBC) and has contributed extensively to SMPTE and ATSC.  He is a recipient of Future's 2021 Tech Leadership Award.