Watch us as we pack the screen with action like you've never seen

[austin_dern]

The NTSC television signal is one of the most remarkable innovations in any way are related to sketchily plotted Ruby/Spears cartoons of the late 1970s. It isn't quite as remarkable as the videotape editing machine, which a close examination of the working principles will show cannot possibly work, but the determined conspiracy of actors and directors for the past sixty years have covered that up so very well that we are left with the NTSC signal to consider. NTSC is an acronym, standing for ``Broadcast Television Information Encoding Scheme'', suggesting that someone wrote down the letters wrong.

This is a gross simplification, of course; in fact they were trying to confuse the PAL standard, which itself stands for ``Systematic Television Alternating Amino Acid''. The systems are easy to tell apart, however: due to PAL being on the metric system television shows and movies play a tiny bit faster in PAL than in NTSC, and as a result the theme songs to Star Trek: Enterprise and Lilo and Stitch: The Series are 625 times better.

The genius of the NTSC system is that it uses 525 lines, which can be found by opening the back of the television set and staring at it with a diffraction grating. Diffraction gratings you can find in your high school physics laboratory, in the fourth drawer over, which is locked. You should get permission before taking one, therefore, as being caught in the middle of taking one will result in awkward explanations. But 525 is a key choice as it is the only number known to be equal to seven times five times fifteen, essential for television technology. Remember that the lines are painted on in a funny fashion, so that all lines whose first digits are even go first, then unpainted lines whose numbers add up to a multiple of three, then multiples of four, then multiples of five, then lines with even last digits, and then finally, line T.

Although the coding scheme was developed by Franciscan monks it has taken revisions gleefully and is now much more powerful than the earliest versions, which were originally unable to handle closed captioning, stereo, color, monaural sound, or pictures of things which are not blurry and contrast-bled Felix the Cat clocks. 486 of the lines are dedicated to the picture, and two for tax records.

Another line is used for the critically important stray dots at the far top and far bottom of cathode ray tubes that clearly represent part of the picture that isn't on the real screen, but that are surrounded by little islands of plain blackness. One of the greatest problems in flat-screen LCD or plasma-screen televisions is what to do with these stray pixels; most sets now simply store the colors up, which is why every eight to ten months the responsible owner must open a drain door, usually under the bottom left of the set, and let the accumulated colors drain. Remember to lay down a disposable rag or a dense padding of paper towels. Failure to do so may result in televisions exploding in brilliant arrays of colors, starting -- based on sales figures of these modern television sets -- sometime around this September. Watch for it on the evening local news.

In the very first line of a frame the name of the television show is printed in all capital letters, in case the frame needs to be entered into evidence. It also contains dental records, nutritional information, an expiration date, and the polarity of visual modulations, in case someone asks. Between lines two and five are stored the closed captioning, and on line six is a random number check to make the captioning of that frame appear in an inappropriate place or to comically misspell the captioning particularly of names. Line 28 serves no purpose except to present you with a nagging sensation that you've seen this episode already; and line 128 gives the suggestion that there might be something better on another channel which you'll never watch.

It may sound complicated, but don't worry: by the time you've read this, it will have already changed.

Trivia: The sixth month of the Babylonian calendar was Ululu. Source: Mapping Time: The Calendar and its History, EG Richards.

Currently Reading: Last And First Men, Olaf Stapledon. Another library book sale book.

Comments

[gafennec.livejournal.com]

It may sound complicated, but don't worry: by the time you've read this, it will have already changed.

Two or three times. Change is in technology accelerates geometrically. :)

[austin-dern.livejournal.com]

I got enough of a headache trying to understand the historical evolution of NTSC while doing research for this.

[orv.livejournal.com]

Even the terminology involved in NTSC is fun. Each line has a "front porch" and "back porch."

[austin-dern.livejournal.com]

It's also very hard to make stuff up about it that hasn't got some essential truth, as well.

I also couldn't find any reference to what lines actually are which, at least on the web; I would have thought Wikipedia would be all over that. I know it doesn't really matter if I just make it all up, but I would have liked to have more facts to build off of.

[tracerj.livejournal.com]

I had to delve into some bizarreness about NTSC to figure out some stumpers about why console videogame graphics with high contrast would have colour-fringes sometimes. The answer... well, it makes perfecty mathematical sense but isn't worth explaining. Here's what I do know...

...NTSC really stands for "Let Someone Else Figure It Out."

[orv.livejournal.com]

If I remember right the upshot of the math is that the chroma resolution is about half the luminance resolution, so sharp edges get color fringes. One solution is to use a component system that separates the two; this was the idea behind SVIDEO. Commodore's monitor outputs also used this trick, which is why their computers looked so much better on their own monitors than on normal composite ones.

When I was doing TV production, and later when I was doing casino CCTV installations, I always tried to steer people away from anything bright red. Red is a bad color for NTSC; it smears and bleeds more badly than any other.

This is all essentially the price we paid for keeping compatibility with black-and-white TV sets.

[tracerj.livejournal.com]

For a composite signal, chroma is a lower frequency than luma as mentioned, and its phase determines the hue at that point. Videogame systems have sharply-defined pixels which are narrower than that frequency, so the cutoff points would call all sorts of lovely interference. Neat thing is, modern game system emulators are starting to incorporate emulation of that nastiness if you like. That's how I got the usericon I have here... check out the 'white' border around it!

And yes, red seems to kill everything.. NTSC, JPEG, MPEG, etc.

[orv.livejournal.com]

For some reason purple seems to be a really bad color for JPEG. Or maybe it's no worse than the others, but my eye notices the artifacts more in purple areas.

One peculiar thing I've noticed about JPEG is the quality seems to depend to some extent on the decoder. I've created JPEGs that looked like trash in one web browser and looked OK in another.

[austin-dern.livejournal.com]

Red generally bothers me because if I have the colors as bright as I'd like, the red parts of, say, the starship Enterprise bridge will bleed into adjacent settings. Make things dim enough that you can't see them and the bleed goes away, but what good is that?

[orv.livejournal.com]

There must be documentation somewhere for all that information they stuff into the vertical blanking interval.

[austin-dern.livejournal.com]

You'd think so, but I couldn't find any online. At one point I was considering buying a real print reference from a second-hand bookstore, but that seemed like too much investment for as long as I'm doing these things for free.

Funny you should mention that ...

[dglenn.livejournal.com]

"In the very first line of a frame the name of the television show is printed in all capital letters, in case the frame needs to be entered into evidence."

Several years ago, I worked on demo software (for, like, taking to trade shows) for a failed competitor to the Neilsen ratings. In this system, the show title, episode title, broadcast date/time, and broadcast station were all encoded in ... either the overscan or during VBLANK, I forget, probably the overscan. I thought the idea was pretty spiffy: the stations inserted the data into the video stream; the set-top boxes were downstream of the VCR, if a VCR was present, and recorded the embedded information as well as the time/date the show was being watched; and the collected set-top-box data was modemed up to the ratings company periodically. So even if the viewers in the house time-shifted shows, they'd be logged as having been watched and the time-shifting info was there if stations cared about that -- and if a taped show got watched three times, they'd know that too.

(I didn't build the system; my contribution was to write PC software (MS-DOS, probably 3.x, if that gives you an idea of when this was) to read the info off one of these boxes in real time and display it along with a cute little animation illustrating what I just described. I remember I found a bug in the Microsoft C compiler along the way. You know how hard it is to get tech-support to take you seriously when you try to report a compiler bug?)

I thought it was a cool implementation of a clever idea, since at that time, as I recall, shows folks taped to watch later pretty much fell through the cracks in the Neilsen data -- I presume they've fixed that in this age of ubiquitous VCRs and DVRs -- but they never managed to get enough momentum to overcome the "but everybody else uses Neilsen" inertia of their market.

Oh, and you probably already know that most techs expand NTSC to "Never Twice the Same Colour" ...

Re: Funny you should mention that ...

[orv.livejournal.com]

And SECAM to Something Essentially Contrary to American Methods. ;)

Re: Funny you should mention that ...

[austin-dern.livejournal.com]

That is an interesting project and yeah, would probably have been useful in working out time-delayed watching.

And yeah, based on my experience I can imagine a report of a compiler bug being believed, oh, never.

I do know the various jokes for NTSC and SECAM (I don't remember a humorous deciphering of PAL, but I'm not at my best this week), not to mention comparisons of them as reflections of social systems and views of what's government responsibility (and sillier things). I just figured anyone who'd know why those were plausible acronym-fittings would have heard the jokes already ...