Monday, August 09, 2010

Speaking Of Sad Colors

Barney the Dinosaur? He's pathological! A "pathological color" for digital television, that is. Or very close; SMPTE* RP 198-1998 defines a test signal that's a kind of sick purple. In digital, it has lousy DC balance, one high bit followed by 19 low bits, followed by the picture breaking up if there's a full screen of it and anything is the least bit awry. By utter chance, the infamous I-love-you thunder lizard is so near that shade that Mr. deMille had better never cut to a close-up for more than a second or two.

There's another pathological hue, a nasty greenish shade, that puts a strain on the signal in another way (I could explain and you could follow, but will you ever lay awake at night trying to work through how twenty low bits followed by twenty high bits, over and over, would produce so much low-frequency energy that it would sneak under the loop filter of a clock-recovery PLL and unlock it? No; either you found that weakness kind of amusing or it left you in cold-hunh land). Sadly, it's not the same shade as Barney's tummy. However, in some (not all -- maybe they were off-model?) images, the character's tummy is awfully close to the color of the "colorburst" reference signal, buried in old-fashioned analog TV signals.

Why is Barney so TV-hued? I dunno. Perhaps it's protective coloration. The picture breaks up and when it clears, the creature is already upon you. Hugging. Ew.
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* Their logo now symbolizes either film-through-digital technologies, or the world shredding film. Oh, Art, Thou mumblest.

3 comments:

Turk Turon said...

I miss SMPTE RS-170A.

Stranger said...

My friend Bill, the chief at the station up the road, bends my ears about digital a lot. It seems I have heard several discussions of those, and similar issues that never cropped up in the days of analog.

I have been out of the business for a generation - and I have never been happier about that than I am now.

Stranger

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