01.16.2007 08:00 AM
Super Bowl uplink sheds light on SD, HD differences

Sports programming has long been recognized as a major driver in motivating some consumers to buy HDTVs, and there's none bigger than the Super Bowl.

In fact, many in the consumer electronics industry see the Super Bowl as the culmination of their annual sales effort to spread the adoption of HDTV sets, before starting the yearlong sales cycle again.

So when a press release from Satellite Technology Systems (STS) of Crystal Lake, IL, crossed the desk saying NFL Films had awarded the company the contract to uplink both HD and SD world feeds of Super Bowl XLI next month from Miami, it seemed like the perfect opportunity to learn a little more about what it takes to uplink such a high-profile sporting event.

HD Technology Update caught up with STS president and owner Charles Spoto as he was preparing for the event.

HD Technology Update: How do you prepare to provide such a widely viewed event like the Super Bowl? In other words, do you take any special precautions to protect against interruptions, glitches, etc. that you might not otherwise take?

Charles Spoto: We will do some pre-testing before the truck leaves Chicago. And then of course we'll be doing some testing starting January 31, which is five days before the Super Bowl, on site in Miami.

We have to test both bands, but there is comfort in knowing that the whole other separate band is available. We can go in either direction with a failure — either for C to Ku or Ku to C. So, we could run a dual path situation for both the Ku- and C-band world feeds on either band if we had to. There's a lot of comfort in knowing we have both bands to work with.

HDTU: According to the press release, you'll be transmitting both SD and HD productions of the game. Why is that the approach being taken rather than transmitting two HDs for redundancy and downconverting to SD for those who need it on the receive side?

CS: There will be a lot of different entities pulling down the signal. Remember, it's the world feed, so you are going to have U.S. network affiliates, national entities and international as well, and there are a lot of different methods of receiving signals. So basically, they put up every possible scenario that they can. Plus, there's going to be international turnarounds, and everybody has a little different capability at the teleports. So by transmitting every possible scenario, everything is covered.

HDTU: The STS truck you'll be using carries both a 4.6m C-band antenna and 1.8m Ku-band antenna. How will each be used?

CS: The C-band antenna part of the truck will be used for HD, and the Ku portion of the truck will be used for the SD world feed.

HDTU: What sort of bit rate will be assigned to both the SD and the HD streams and why?

CS: I don't have the spec sheet in front of me, but the SD stream will be roughly 18Mb/s, and the HD stream on the C-band will be roughly 30Mb/s.

HDTU: Tell me about the truck's split power system.

CS: The truck has a split power system that allows us to run both bands independently on power. That way we won't lose the security of having a redundant transmission system in case of a failure to one side of the split power system.

We have shore power and can provide the same voltages off our Kohler onboard diesel generator.

HDTU: Your press release says the truck that will be used can provide up to 20 digital satellite paths at once. Will these be used and if so, how?

CS: We will not be using that many paths for this show. That's just the capability of the truck because of the larger antenna.

HDTU: The Satellite Users Interference Reduction Group recently conducted a test proving the ability to insert data identifying the satellite uplink and location into a video transmission. How common is it to experience intentional or unintentional interference? Does it vary from C-band to Ku-band, given that a lot of the Ku-band transmissions in television are one-time SNG shots?

CS: As far as the interference on C band, as a company I don't know that we have a personal experience with interference. But I do know of some cases of interference in C band. It's affected various teleports or their feeds, and that was recorded by a group of earth station engineers.

On the Ku-band side, we have experienced interference in the past. Most of that is from people accessing the wrong satellite or a few other things, including incorrect cross polarization, accessing the wrong satellite or accessing at the wrong frequency.

When you are talking about the interference situation, the ability to reject interference can be done with our C-band antenna because we have higher gain and more power capability at the flange. So, by having that capability, we can operate at full saturation. If somebody does come up on wrong transponder or hits us with a signal from an adjacent satellite, we have enough headroom up on the bird to reject that interference, which is useful in a world feed situation.

With the Ku, we can do full saturation. However, digital carriers sometimes operate at a much lower power, so you're going to be susceptible. For doing world feeds, it would be very dangerous to use Ku as a primary source for interference.

HDTU: Besides the bandwidth differences, what are the differences between uplinking HD and SD, especially in terms of preparing for both?

CS: The HD signal requires a much wider bandwidth and requires much more power.

We do a lot of pre-monitoring of the HD signal in the truck before we even go on the satellite. Because of the high bit rates involved with high definition and being that the encoders are basically a super computer, you have to make sure the integrity is there in the signal. And we monitor that as well with a backup measurement device called a bit stream analyzer in the truck. We monitor the signal hours before our feeds to look for any errors that would potentially come up.

There's a lot more information being processed with HD obviously, so it's much more critical to pre-monitor the signal.

If there's a problem, we determine where the breakdown is in the signal, whether it's the incoming HD-SDI signal or the processing in the encoder, which we can do with the Pixelmetrix bit stream analyzer. We can take corrective measures at that point.

The problems can vary. It can be a software glitch that potentially is corrupting the signal or a weak HD-SDI signal or a corrupted HD-SDI from the production truck.

Tell us what you think!
HDTU invites response from our readers. Please submit your comments to editor@broadcastengineering.com. We'll follow up with your comments in an upcoming issue.



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