General > General Technical Chat

The Mehikon - broadcast TV color eraser

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NiHaoMike:

--- Quote from: Ultrapurple on August 25, 2020, 10:08:31 am ---The 50/60Hz thing lives on today. I was recently looking at the possibility of acquiring a '4k' TV. Reading the small print in the spec, it's amazing how many of them quote a 120Hz refresh rate for the panel. What's wrong with that? I live in a 50Hz country and if you watch 50Hz (100Hz) material on a 60Hz (120Hz) screen you get awful judder. Once you see it you'll hate it forever.
--- End quote ---
The app mpv can perform time domain interpolation.
https://mpv.io/manual/stable/#gpu-renderer-options

--- Quote ---I have yet to see a domestic TV that specifically says it adapts the panel refresh rate to suit the source material (though I admit I haven't done an exhaustive market survey).

--- End quote ---
Look for "adaptive sync" or "G-Sync" in the specifications.

BrianHG:

--- Quote from: tooki on August 25, 2020, 05:18:51 am ---
--- Quote from: BrianHG on August 24, 2020, 11:14:12 pm ---
--- Quote from: tooki on August 21, 2020, 05:16:57 am --- (How many CRT HDTVs are there out there, really??)

--- End quote ---
What the hell.  My 37inch multiscan Mitsubishi back in 1993 did HDTV in RGB fine once the standard became available.
Ok, well, brand new at the time, it was a 20K$ monitor.

And yes, 5 years later when I could finally reliably play DVDs on a PC, I ran the screen at 72fps progressive making the motion in movies perfectly v-synced.  Well, once in awhile, you could catch a dropped frame as the video card's 72Hz wasn't in perfect tune with the DVD player software of the time which I believe locked onto the sound card's 48KHz clock since it had to sync AC3 without disruption.

My desktop screens were all running at either 96Hz or 120Hz.  No flicker at all.

--- End quote ---
I wasn’t talking about computer displays, which is why I said “CRT HDTVs”, not just “CRTs”. I assume your 37” Mitsu was a computer display (or broadcast monitor), not a TV, right?

Anyhow, I didn’t say there were no CRT HDTVs. Just a vanishingly small number, compared to the number of flat-panel HDTVs sold over the years.

--- End quote ---
Ok, the 37inch was a studio screen/monitor with NTSC/PAL Y/C. YUV,  RGB TTL and Analog inputs.
The most HDTV CRT TVs which were sold to consumers were pretty much all  in Japan as they had OTA analog HDTV back then.

vk6zgo:

--- Quote from: tooki on August 25, 2020, 05:24:03 am ---
--- Quote from: vk6zgo on August 25, 2020, 02:17:51 am ---With the invention, & subsequent miniaturisation of frame stores, system conversion has become a trivial task.

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Well, I wouldn’t call it trivial. If the sole thing you’re converting is color system (e.g. PAL <-> SECAM), then it’s trivial. If you have to rescale a resolution, it’s a smidgen harder. But any time you have frame rate conversion or interlacing involved, it gets a LOT hairier. Good converters do similar things as the motion smoothing in our TVs: object tracking and interpolation. If you don’t do this, you get jerky movement and (on interlaced source material) combing.

--- End quote ---

TV Networks have been converting from PAL/SECAM 625 to NTSC 525 & vice versa since the mid 1970s.

The earliest standards conversion units back in 1967 converted between 625 BW & 405 BW, but maybe did it "on the fly", by strategically dropping lines, rather than with frame stores.
(Granted, this was only line rate conversion.)

The last generations of telecine chains could convert from "sixteen & two thirds" fps to 25 fps, so that old film of the Kaiser's armies looked suitably ominous, instead of having them prancing around like Smurfs, as just running the old film at 25 fps did.

Of course, telecine has the advantage of being a series of full frame stills, unlike a normal analog video frame, where the movement progresses line by line.

The "frame grabbers" widely available in the 1990s had problems with this.
A test card, or a frame sourced originally from cine film would "grab" perfectly, but video originated by a TV camera would blur (or perhaps "smear" is a better term) on rapid movements.

NiHaoMike:

--- Quote from: vk6zgo on August 25, 2020, 11:36:05 pm ---The "frame grabbers" widely available in the 1990s had problems with this.
A test card, or a frame sourced originally from cine film would "grab" perfectly, but video originated by a TV camera would blur (or perhaps "smear" is a better term) on rapid movements.

--- End quote ---
So basically equivalent time sampling?

vk6zgo:

--- Quote from: NiHaoMike on August 26, 2020, 02:27:13 am ---
--- Quote from: vk6zgo on August 25, 2020, 11:36:05 pm ---The "frame grabbers" widely available in the 1990s had problems with this.
A test card, or a frame sourced originally from cine film would "grab" perfectly, but video originated by a TV camera would blur (or perhaps "smear" is a better term) on rapid movements.

--- End quote ---
So basically equivalent time sampling?

--- End quote ---

Maybe it's just another way of looking at things, as scanning does "sample" the scene presented to the camera, & each tiny increment of movement is a change from line to line, so maybe it can be regarded as being higher in frequency than the "sample" rate.

But, as an analog person, I tend to think in tems of it being to do with the fact that analog TV doesn't actually present 25 or whatever frames per second as individual still pictures, but presents a number of lines which take finite time, during which motion is happening in the live scene the original camera is seeing.
As with many other things in analog TV, it depends upon human physiology.
(Dogs, with their different vision characteristics, did not recognise their kind on analog TV--- they can with digital TV)

"Persistence of vision" prevents us from seeing this happening as other than a smooth movement over multiple frames, but the "grabber" can see it, & in endeavouring to record it, tries to capture the xhange over multiple lines.

I'm afraid I never went into how the cheaper "frame grabbers" work.
Broadcast standard equipment seems to be able to do this without problems-- these were the cheaper ones we used mainly to grab & in turn source announcement "slides" as part of the emergency stuff at the transmitter.
Scenery  & such, without movement also "grabs" OK with these.

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