The Mehikon - broadcast TV color eraser

[newbrain]

With regards to CRT TVs? Absolutely. It’s clearly visible, especially in peripheral vision.

I can relate to this. No superpowers, but a kid I was nauseated by TV flicker (50 Hz), and I could not understand how people endured fluorescent lights.

Now, it's been ~10 years since I looked at a CRT (wow, never thought of that!), but for fluorescent lights at least, I don't notice it any longer. I changed for sure, they might have too...

[eti]

Was it designed in "Mehiko"? 

[NiHaoMike]

..and you would get horrible flicker as a bonus

The display can be refreshed 2 or more times per frame. That's how classic 24 FPS movie projectors don't flicker.

All that shenanigan just because someone wanted even 30Hz ?

Checkboarding and frame rate are independent. The best solution is to just do 1080p at 60 FPS and compress more to stay within bandwidth limits, but if sending half frames at 60Hz has to be done, the artifacts introduced by a checkboard pattern is much less noticeable than interlacing. Actually, checkerboarding really is a slight modification to interlacing.

but for fluorescent lights at least, I don't notice it any longer. I changed for sure, they might have too...

They definitely have, pretty much every CFL has used an inverter since the early 2000s.

[BrianHG]

(How many CRT HDTVs are there out there, really??)

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.

[vk6zgo]

With the invention, & subsequent miniaturisation of frame stores, system conversion has become a trivial task.

A bit off topic, (but close to the sub-topic of things the eye can perceive), have you ever turned your head quickly whilst gazing at an analog 'scope screen from mid-distance?

It looks as if the time/div setting has been reduced &, to me, is most obvious when looking at a sine wave-----the strobing effect of your motion makes you see less cycles spread out further on the screen.

I don't think it would work with a DSO, though.

[tooki]

(How many CRT HDTVs are there out there, really??)

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.

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.

[tooki]

With the invention, & subsequent miniaturisation of frame stores, system conversion has become a trivial task.

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.

[igendel]

Funny thing, I've heard a lot about the Mehikon (I'm just a couple of years too young to have any personal recollection of it) - but it always bugged me, how color can be restored to a B/W picture, and no one could explain so I stopped asking I guess. Now I finally understand... thanks! 

[Ultrapurple]

Fascinating info from basinstreetdesign - thank you!

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.

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).

As an aside, the first couple of generations of Roku-based boxes used for the NowTV service were hard-wired 60Hz - which made as much sense as a chocolate teapot because all the native source material (basically, UK broadcast TV) would be 50Hz.

I find it quite nausea-inducing to watch an American show that has been standards converted from 60Hz to 50Hz, converted back to 60Hz in the Roku box, and finally played on a 50Hz screen. Yet my partner doesn't even notice it.

[tom66]

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).

Perhaps it's different nowadays, but my 2012 Panasonic plasma has a 100Hz, 60Hz and 72Hz mode.  The 100Hz mode is for 50Hz (frame doubling with low flicker), the 60Hz mode is of course for NTSC/60Hz content and the 72Hz mode is for frame-tripled 24fps content.  You could see, on an oscilloscope, the drive waveforms changing between these modes, with the screen briefly blanking.  The reset pulse, ramp timings etc all changed slightly and indeed the '100Hz' and '72Hz' modes had a slightly lower black level as they could refresh the panel more often without 'mal-discharge'.

My older 2008 Panasonic plasma had 48Hz, 50Hz and 60Hz modes for a similar purpose, although the 48Hz mode was very close to the flicker-fusion point and so you often could see flickering in your peripheral vision.

[NiHaoMike]

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.

The app mpv can perform time domain interpolation.
https://mpv.io/manual/stable/#gpu-renderer-options

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).

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

[BrianHG]

(How many CRT HDTVs are there out there, really??)

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.

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.

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]

With the invention, & subsequent miniaturisation of frame stores, system conversion has become a trivial task.

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.

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]

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.

So basically equivalent time sampling?

[vk6zgo]

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.

So basically equivalent time sampling?

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.