Upconversion: It’s More Than Meets the Aieeee!! - TvTechnology

Upconversion: It’s More Than Meets the Aieeee!!

You might not have noticed that it’s no longer 1996.
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You might not have noticed that it’s no longer 1996. Yes, of course, as you’ve no doubt just figured out, the theme of my rant this lunar cycle is upconversion.

Did you ever notice how lots of folks put the wrong year on checks in early January, but you don’t see anyone writing December 32 much? That’s one of the great unknowns of the human mind. But, if our minds were simple enough for us to understand, they’d be too simple for us to understand them.

Anyhow, I don’t think anyone is still dating checks as 1996 these days. And WRAL-DT now has more than one video encoder.

If you look up the history of DTV, WRAL is sometimes listed as the first DTV station. Methinks they were the first to transmit bits according to the ATSC standard, so the “D” is well earned.

THE ‘MODEL’ STATION

As for the “TV,” I’ve always been taught that TV is pictures and sound, and methinks that when WRAL-DT went on the air they had encoders for neither. It’s tough to turn unencoded bits into pictures and sound, so, as far as I am—or should I say we are—concerned, the real first ATSC DTV station was WHD-TV, the “model” station, the first with video and audio encoders.

Now, then, I don’t want to cast any unfounded aspersions, and what I’m about to mention took place maybe a decade ago —and, anyhow, who knew back then— but, if Nellie the neuron recalls correctly, there was a little hiccup at WHD-TV one day. They transmitted some incorrect PSIP info.

It wasn’t that it messed up their transmissions; it knocked out other stations on consumer receivers. But that’s what the model station was really intended for; it was supposed to figure out what could go wrong so others could avoid it. I say, “Way to go!” to whoever screwed up the PSIP; if it hadn’t been done, we’d never have known what to avoid.

It wasn’t just the PSIP that was a problem in the old days; I recall some old receivers that would freeze if a broadcaster simply changed video format, and that’s something broadcasters are supposed to be able to do. And that gets me up to my point, if I have one—not counting the one at the top of my head.

THE INCONVENIENT TRUTH

Today, if Nellie has read the calendar correctly, is in 2007. That means it is 11 years after 1996. It is nine years after WFAA-DT went on the air in Dallas and knocked out some heart monitors that had been sharing its channel at Baylor Medical Center. It is coming up on eight years since WHD-TV went off the air on account of lack of funding or interest or something of that sort. It is a couple of years since the “tuner mandate” started, and it’s coming up on half a year after it kicked in 100 percent (all devices with TV tuners imported to or shipped interstate in the U.S. have to have ATSC receiving circuits).

I can’t claim to have tested every one of those 2007 ATSC receiver circuits, but I’ve got bad news and good news about the ones that I’ve run through the wringer. The bad news includes the inconvenient truth that they come in a range of qualities. Some work in places where others don’t. I’ve also heard tell that some hang up when a broadcaster transmits more than 12 hours worth of electronic program guides. And I’m still waiting for dual-stream audio decoders to allow the commentary and other features that have been in the ATSC standard for a dozen years. But the good news is that not a single one that I’ve tried has had any problem when a broadcaster switches between HD and SD.

To be sure, there were receivers sold in the early days that had such a problem. Methinks I mentioned that just three paragraphs ago. In those old days, the good old Consumer Electronics Manufacturers Association (it wasn’t CEA yet) reported sales of thousands of digital television receivers, but it turned out that almost all of those had no way to receive an ATSC signal. These days, the CEA reports sales of millions, and, thanks to that 100 percent tuner mandate, they’ve all got some kind of ATSC capability.

SO FAR, SO GOOD… AND BAD

Here’s my conclusion, based on what I just wrote: It’s possible that there is some early adopter somewhere still using a DTV receiver that freaks out when a broadcaster changes video format. That same receiver probably also freaks out whenever PSIP is updated. And may higher powers help us if that receiver ever sees an SD signal with the global standard 720 active samples per horizontal line. Meanwhile, everyone else getting DTV ain’t got a problem with video format changes.

So, for that one early adopter—and maybe also on account of their master control equipment not being multiformat or their video encoders not being auto-sensing— broadcasters are upconverting SD to HD so they get to transmit one common format per encoder. So far, so good. It’s probably cheaper for a broadcaster to buy an upconverter or two than to re-do master control and change encoders. But here comes the bad part.

Upconverted SD has got lots more high-frequency energy than true HD. That’s on account of the upconverters guessing at what might be edges and putting in nice, sharp transitions there the way old image enhancers used to do in analog NTSC.

MPEG encoders view high-energy high frequencies as high-information content, and high-information content stresses encoders, resulting in blockiness and other artifacts. Translation: Upconverted SD can look worse than plain SD, let alone HD.

Want to have an SD subchannel? Go for it. But, please, if you’re going to transmit HD, how about making sure it’s really HD? Your viewers—not just the one with the 1998 receiver—will thank you.