Survey: 60Hz TVs running at 24Hz

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markfilipak
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Survey: 60Hz TVs running at 24Hz

Post by markfilipak »

SUMMARY: It appears there's really no purpose to be served by a survey, that just about no one has a so-called "Adaptive Sync" TV.

It's not a secret that Blu-ray movies look better on 24Hz TVs. What surprised me was, though my TV's manual says it runs solely at 60Hz, and though I could connect via HDMI under Windows solely at 60Hz, I can switch my Sharp TV to 24Hz via a NVIDIA utility! ...And it does look better.

Are all so-called 60Hz TVs capable of 24Hz video display? What's your experience been?

Please respond to this survey, even if you don't know. It will help survey coverage.

If you want to know how I did it, kindly email off-list via private message so that this survey space stays simple.

Thanks & Warm Regards,
Mark.
Last edited by markfilipak on Thu Mar 19, 2020 10:32 pm, edited 1 time in total.

mduell
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Re: Survey: 60Hz TVs running at 24Hz

Post by mduell »

Most can't do actual 24Hz. Some can do 120Hz, and just display the image 5 times.

markfilipak
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Re: Survey: 60Hz TVs running at 24Hz

Post by markfilipak »

@mduell,

Sure. 120Hz would be perfectly fine -- the result is a picture rate of 24 pictures per second -- 5 frame repeat doesn't change that because 5 frame repeat is not telecine.

My TV is 23Hz to 76Hz. 60Hz (assumed: 60Hz/1.001) is native. 24Hz is not native for my TV; my TV definitely telecines 24 FPS streams.

For the sake of advice to people transcoding for the absolutely best picture I'm going to assume that their 60Hz TVs also cannot natively run at 24Hz, that they telecine 24 FPS content. I mean, it currently makes sense from a product marketing POV that a TV telecine.

However, from a hardware design standpoint (my perspective) there's no reason why a TV couldn't be designed to run natively at 24Hz or 60Hz or, really, anything. All that would be required is sythesized tuning: a high frequency time base & a PLL in lieu of fixed crystal oscillators, much as is done with sythesized FM radio tuning.

Going further down the hardware design possibilities, there's every reason why some (future) mode of operation could be created that would treat a TV as a random access device instead of as a serial device -- just imagine the amount of compression that would be possible with such a random access picture mode -- just imagine the stream rate of such an approach. Right now, flat panels are serial. Perhaps some day the industry will realize that, like memory, like disk drives, flat panels should be random access. We have a long road ahead. If the video engineers stopped taking tiny steps and bravely stepped out to do something really innovative, we'd all be a lot better off.

mduell
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Re: Survey: 60Hz TVs running at 24Hz

Post by mduell »

Some TVs do allow for a range of inputs, to support Adaptive Sync. The hardware is more expensive than something that only does 60Hz.

markfilipak
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Re: Survey: 60Hz TVs running at 24Hz

Post by markfilipak »

mduell wrote:
Thu Mar 19, 2020 9:16 pm
Some TVs do allow for a range of inputs, to support Adaptive Sync. The hardware is more expensive than something that only does 60Hz.
"Adaptive Sync", eh? So that's what they're calling it. The difference in hardware cost: maybe $2 or $3 -- the difference is mostly a higher frequency, more expensive crystal -- phase lock loops require higher frequencies to manage jitter -- and whether the PLL can be/is built into the on-board processor or must be implemented using discrete components. Yes, I miss being an engineer; this is an interesting time.

mduell
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Re: Survey: 60Hz TVs running at 24Hz

Post by mduell »

It's a lot more than just a $3 crystal. The earlier nVidia implementations with G-Sync required an FPGA.

markfilipak
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Re: Survey: 60Hz TVs running at 24Hz

Post by markfilipak »

mduell wrote:
Thu Mar 19, 2020 11:46 pm
It's a lot more than just a $3 crystal. The earlier nVidia implementations with G-Sync required an FPGA.
Well, I once implemented a PLL using an existing, on-chip DAC and added a filter capacitor (integrator). I guess that wasn't possible with NVIDIA's previous design. Oh, well. Thanks for the discussion.

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