Survey: 60Hz TVs running at 24Hz

[markfilipak]

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.

[huhn]

pretty much all sony 60 HZ tvs are able to present 24 hz correctly all 60 HZ Tv are able to accept this type of signal but they usually unable to display them correctly which is called 3:2 judder.

BTW. because you can't select 120 hz doesn't mean the panel is run at that refreshrate.

there is a very easy test to check if a panel is 120 hz send 60 HZ and try to enable motion interpolation if it works by giving you a horrific image it's pretty much proven that the panel is 120 HZ.

[markfilipak]

pretty much all sony 60 HZ tvs are able to present 24 hz correctly all 60 HZ Tv are able to accept this type of signal but they usually unable to display them correctly which is called 3:2 judder.

That's upconverting to 60p. It's not 24p.

So, Sony 60Hz (or 120Hz) TV's do not play 24p, is that what you say?

[huhn]

no sony found a way to display 24p correctly on 60HZ panels the majority can't do that they need 120 HZ display to do that.

if you are using a custom resolution to force 24p you are playing with fire and this has to be an low end TV: https://www.testufo.com/frameskipping

That's upconverting to 60p. It's not 24p.
don't tell me that tell that them.

[markfilipak]

no sony found a way to display 24p correctly on 60HZ panels the majority can't do that they need 120 HZ display to do that.
As you probably already know, when fed a 24 FPS video (such as Blu-ray), a 120Hz TV simply repeats each frame 4 times (total: 5 frames, i.e., 120Hz/24Hz = 5). The result is perfect 24 FPS. As I know you know, when fed a 24 FPS video, a 60Hz TV coverts each 4 frames to 10 frames,1, to 30 FPS via 2:3 pulldown (i.e., 30Hz/24Hz = 5/4) followed by, 2, repeating each resulting frame 1 time (i.e., 60Hz/30Hz = 2).
if you are using a custom resolution to force 24p you are playing with fire and this has to be an low end TV: https://www.testufo.com/frameskipping
I have a comment and a confession. Comment: I'm not forcing it. According to the MonInfo application, the TV reports 23Hz to 76Hz in its HDMI capabilities. Confession: After I wrote to you last, I finally pulled my head out of my a$$ and realized I already have everything I need to determine whether my Sharp TV can operate in native 24Hz mode. It can't. I now know for sure that it's native 60Hz, and that, when fed 24 FPS, it's doing 2:3 pulldown.

[Blue_MiSfit]

Probably 2:2:2:4 pulldown, unless you see a ton of aliasing, in which case it is indeed 3:2 but that would actually be harder.

[huhn]

is called 3:2 but with progressive frames.

i didn't make these names up

[SeeMoreDigital]

Many modern TV's, especially 'smart' TV's are able to automatically adjust their panels frequency/refresh rate to match the frequency of source content.

However (unless things have changed in recent years), computer graphics cards puke out a fixed frequency/refresh rate - which would have to be manually adjusted (if supported) to match the frequency of source content.

That being said, there's way too much content out there that's been poorly encoded and incorrectly flagged. So it's always good practice to check the source content for errors!

EDIT: It may also be worth pointing out that 24Hz (24fps) encoded content is actually pretty rare, even on UHD disc's. Indeed, most (progressive encoded) movie content runs at 23.976fps (ie: 23.976Hz). And if you force content encoded at 23.976fps to be displayed at 24Hz, it introduces other issues ;)

[kolak]

TVs always (well at least in last 20 years) been able to switch to "source native" fps, including 23.976p (as long as supported). This is what most monitors are unable to do, so they're not very good for watching movies.
Modern TVs quite often do multiple of native fps, or now frame interpolation (which always leaves some artefacts).
Best way of watching 24p is black frame insertion and running at eg. 72Hz or 120Hz (this is what happens at cinemas). Some TVs do it. Old Pioneer Kuro used 72Hz for 24p source and it worked very well.

If TV is trying to display 24p source at 60Hz then it's crap TV :)

[huhn]

If TV is trying to display 24p source at 60Hz then it's crap TV :)

how helpful.
the number of these TV is very high and even present in expensive close to flag ship TVs because how do you display 24p on a fixed 60 HZ panel?

[wonkey_monkey]

how helpful.
the number of these TV is very high and even present in expensive close to flag ship TVs because how do you display 24p on a fixed 60 HZ panel?

By not using a fixed 60Hz panel.

[Asmodian]

It is surprising how many fairly high end TVs from the last few years do use fixed 60 Hz panels. :(

[wonkey_monkey]

Maybe that's a US thing. A lot of them still don't support PAL, to the best of my knowledge.

Given that European TVs have to look good at 50Hz anyway, maybe they're more likely to be multi frequency.

[huhn]

nothing todo with that.
there are just a lot of panels that are limited to 60 HZ but they can do 50 Hz just fine.

[wonkey_monkey]

nothing todo with that.
there are just a lot of panels that are limited to 60 HZ but they can do 50 Hz just fine.

A panel that's fixed to 60Hz (if that's what you mean by limited) can't do 50 Hz "just fine" any more than it can do 24Hz (i.e. it could possibly do it, but only badly).

Last I heard, most US TVs still won't handle 50Hz signals at all, "just fine" or not.

[huhn]

and i read (panel specs included)and tested this far to much.

50 is not an issue it can be disabled by design but the panel doesn't have an issues which that they use the same panels in the eu and the USA.
are there cheap panels that can't do sure the top 5 panel producer panels with 50/60 hz.

sony fixed this issue they can do 24p with 60 panels the same 60 hz panels as other menufacture they don't produce LCD (they have a professional RGB OLED fab but ignore this) if they figured out doing 48 is not far from 50 or some thing like that i don't know that just how it is most TV with a 60 Hz panel can't do 24p there is no good reason for that but that's reality.

[Asmodian]

For LCDs refreshing at 24Hz can be technically bad. They cannot hold the liquid crystal in one orientation long term so you get apparent flicker as the pixels drift and then snap back at the next refresh. Of course, you could use 48Hz with frame doubling because most LCDs don't drift much in 21ms but even that could be too slow for a particular panel. It is also more expensive to support more refresh rates because you need to tune the refresh electronics for each refresh rate, requiring a better controller and more work up front. Not much more expensive today but you do have to spend something to support each refresh rate. :p

That said, I suspect most TVs don't that support 50Hz today could but don't as a simple region locking mechanism.

[kolak]

how helpful.
the number of these TV is very high and even present in expensive close to flag ship TVs because how do you display 24p on a fixed 60 HZ panel?

https://www.rtings.com/tv/tests/motion/24p

[kolak]

That said, I suspect most TVs don't that support 50Hz today could but don't as a simple region locking mechanism.


Nothing more than "politics".
Europe had all fps support for very long time now.

[huhn]

2018 was a bad year to buy a TV.

[wonkey_monkey]

Overall, 24p judder is not a major problem; most people will never even notice it.

True, possibly because Americans have been used to 24p judder since the days of CRTs and 3:2 pulldown.

Edit: there's a neat test on that page where they send an alternating 24p signal to the screen and take a long exposure photograph. If there is judder, it shows up in the photo as a bias towards one of the two frames. Neat!

[huhn]

why someone will ever need such a test to see something obvious like this is beyond me.

and there are other way to test this beside using additional hardware.

[wonkey_monkey]

Because it's not obvious to everyone.

[Stereodude]

2018 was a bad year to buy a TV.
Why do you say that? There were some very fine TVs sold in 2018.

For LCDs refreshing at 24Hz can be technically bad. They cannot hold the liquid crystal in one orientation long term so you get apparent flicker as the pixels drift and then snap back at the next refresh. Of course, you could use 48Hz with frame doubling because most LCDs don't drift much in 21ms but even that could be too slow for a particular panel.
That's not really true. The fluid is effectively used as a capacitor that holds the transistor in the state set by the panel drivers. The combination will hold the for quite a while (in terms of ms). It takes seconds for the image to fade if you stop refreshing the transistors.

It is also more expensive to support more refresh rates because you need to tune the refresh electronics for each refresh rate, requiring a better controller and more work up front. Not much more expensive today but you do have to spend something to support each refresh rate. :p
That's why they refresh the panel at 120Hz or 240Hz in good LCD TVs. They're not changing the actual drive rate for the panel much. All expected North American content is a multiple of those that divides in evenly into 120Hz.

That said, I suspect most TVs don't that support 50Hz today could but don't as a simple region locking mechanism.
What do you mean by support? I can input p25 and p50 into my US model LCD Sony TV. They are supported frame rates. I haven't bothered to confirm if it switches the panel drive to 100Hz. It wouldn't surprise me if it does. The European model of the same TV has to support p24 properly in addition to 50Hz content so it has to switch between 100Hz and 120Hz drive.

Because it's not obvious to everyone.
It pretty much is if you put two displays side by side. One with a 60Hz refresh rate and one with a refresh rate that's a multiple of 24Hz and show content with motion and pans in them they will quickly realize they don't look the same if told to compare them. They probably won't be able to tell you why, but they will see the difference.

[huhn]

because in 2018 samsung didn't produce a lot of 120 HZ panels and samsung is pretty much the biggest producer of VA panels leaving you with mostly 120 Hz IPS.


does that mean all TV are bad? no clue why you would come to the conclusion.

[SeeMoreDigital]

@markfilipak,

Out of interest... What device are you using to play your media files? And what's your Sharp TV's model number?

[Asmodian]

That's not really true. The fluid is effectively used as a capacitor that holds the transistor in the state set by the panel drivers. The combination will hold the for quite a while (in terms of ms). It takes seconds for the image to fade if you stop refreshing the transistors.

Lots of the early VRR monitors had this issue. When the frame rate drops too low they flicker and it was solved by automatically refreshing the display twice when at low frame rates. The image is still there, the pixels only drift slightly, but it is enough to notice it frame to frame below 30-40 Hz, at least with many current LCD panels.

What do you mean by support? I can input p25 and p50 into my US model LCD Sony TV. They are supported frame rates. I haven't bothered to confirm if it switches the panel drive to 100Hz. It wouldn't surprise me if it does. The European model of the same TV has to support p24 properly in addition to 50Hz content so it has to switch between 100Hz and 120Hz drive.

I think most do, my recent LGs have supported 50Hz properly. Just some don't. :p

[SeeMoreDigital]

I think most do, my recent LGs have supported 50Hz properly. Just some don't. :pYes they do...

[Asmodian]

Yes they do...

You saying all TVs support 50Hz? Are you sure? :confused:

Very recent TVs do seem to support 50Hz most of the time but I would still not assume they all do. Maybe it is simply very cheap ones that don't care, and not some region locking nonsense. Using refresh rate support for region locking is hopefully out of date today.

[SeeMoreDigital]

You saying all TVs support 50Hz? Are you sure? :confused:

Very recent TVs do seem to support 50Hz most of the time but I would still not assume they all do. Maybe it is simply very cheap ones that don't care, and not some region locking nonsense. That idea is hopefully be out of date today.All TV's in Europe support 50Hz (25 progressive frames and 50 interlaced fields per second)...

[Asmodian]

Well, of course! I was only talking about US TVs. Region locking by not supporting 50 Hz wouldn't make any sense with TVs sold in Europe. :confused:

[SeeMoreDigital]

Well, of course! I was only talking about US TVs. Region locking by not supporting 50 Hz wouldn't make any sense with TVs sold in Europe. :confused:As far as I know... All 'smart' Panasonic and LG televisions sold worldwide are capable of supporting 50Hz. Although the feature might be locked out and will require a visit to the service menu.

[microchip8]

I have an el cheapo Panasonic TV with an Innolux MVA panel. My NV Shield is set to 24 FPS and when I switch to it, my TV reports 24 Hz. Not sure whether it is true 24 Hz or it upconverts. Regardless, all looks fine here

[huhn]

panasonic well that's easy to test.

just actived pure direct mode and it can't do 24 HZ correctly anymore that's by design don't ask me why.

cheap version are sometimes just that brand in name but produce by someone else but still relative easy test.

there are other ways to test this but i'm not going into that.

[microchip8]

I know that the budget models are produced by the Turkish Vestel but mine is actually made by Panasonic itself in the Czech Republic. I do not use Pure/Pixel Direct as it makes the picture worse. I'm not too concerned with doing native 24 Hz or not. As long as it looks good to me, I'm happy :)

[Stereodude]

You saying all TVs support 50Hz? Are you sure? :confused:

Very recent TVs do seem to support 50Hz most of the time but I would still not assume they all do. Maybe it is simply very cheap ones that don't care, and not some region locking nonsense. Using refresh rate support for region locking is hopefully out of date today.
You've yet to define what "support" means in the context of your usage. Is it simply take the format on the input and put an image on the screen, or take the format on the input and display it at a refresh rate that is a multiple of 50Hz?

[Asmodian]

I meant accept the format as input and have an entry for it in their EDID. Sorry, I didn't think some TVs lacking support for 50Hz would be controversial. There used to be many TVs sold in the US that would not accept a 50 Hz signal at all, no attempt to display an image when provided with a 50Hz signal. Maybe this is no longer true, and all TVs sold in the US support 50Hz input, but I wouldn't assume that without first making sure if you need 50Hz. Historically 50 Hz support has been surprisingly bad in the US.

On that same note, I also would not be surprised if some TVs that do support 50Hz input end up displaying it with a 60 or 120 Hz refresh rate. I don't have any examples of this though, hopefully it isn't true.

[kolak]

I may be wrong, but a panel with eg. 120Hz max refresh rate is not fixed to it (or doesn't have to). It can operate at anything lower as well. It's up to manufacture to give such an ability or not. It's even more true for monitors which support adaptive sync. If I'm correct this seems to be coming to TVs as well (not only gaming monitors).
50Hz in USA use to be almost non-existing. No idea how it's now.

[Stereodude]

I may be wrong, but a panel with eg. 120Hz max refresh rate is not fixed to it (or doesn't have to). It can operate at anything lower as well. It's up to manufacture to give such an ability or not. It's even more true for monitors which support adaptive sync. If I'm correct this seems to be coming to TVs as well (not only gaming monitors).
50Hz in USA use to be almost non-existing. No idea how it's now.
It's still non-existent for normal people in the US. I only have it from some concert Blu-rays that were shot as 1080p25 and converted to 1080i60 that I restored back to 1080p25.

[SeeMoreDigital]

It's still non-existent for normal people in the US. I only have it from some concert Blu-rays that were shot as 1080p25 and converted to 1080i60 that I restored back to 1080p25.
If I was a conspiracy theorist, I would postulate that way back in the DVD days, TV's (and players) destined for the North American NTSC market were locked out of PAL 50Hz support, so they could not take advantage of the (technically) 20% improvement in picture quality over their NTSC counterparts!

The organisations controlling the development and distribution of DVD including how their images are transported from player to display, were and still are... pretty anal!

[kolak]

It's obvious it's all down to politics and money. Probably Hollywood studios are behind it.

[hello_hello]

Nothing more than "politics".
Europe had all fps support for very long time now.

I'm in PAL-land (Australia) and I think every Bluray player and TV I've come across is 60Hz "at heart", but capable of 50Hz, or the TV's in NTSC land are 60Hz, with 50Hz disabled, however you want to look at it.

Both Bluray players here (Sony and Samsung) display their own menus at 60Hz. One only switches the TV to 50Hz when playing a 25fps disc, while the other is also clever enough to switch the TV to 50Hz when playing 25fps video via USB. I'm not sure which refresh rate the TV uses when playing video via it's internal media player. I've never tested it but most of the video I use it for is 23.976fps/24fps anyway.

My LCD computer monitor can accept either a 60Hz or 50Hz input.

NTSC support has been common for so long, that back when DVD rentals were a thing, I'd occasionally rent a DVD and not realise it was NTSC until I looked more closely at home, but even my old CRT could switch to "NTSC mode" and the DVD player didn't care.

[kolak]

Europe is the same, but USA is not. Their TVs (not players) don't really support 50Hz.

[markfilipak]

@markfilipak,

Out of interest... What device are you using to play your media files? And what's your Sharp TV's model number?

Sorry to take so long to reply (I've not been able to figure out doom9 and I don't get notifications).

I play via MPV running in Win10. The Sharp TV is connected via NVIDIA driven DisplayPort. The TV model is LC-42LB261U.

[markfilipak]

Sorry for getting really technical but this is a really technical subject.

If you're tired of seeing crap video and you find that my "best possible video" obsession interests you... I need your support trying to pry details out of the various project developers. There's power in numbers. Contact me here or via PM.

KEY: (In lieu of useless terms like '30i' and '24p'...)
KEY: "fps" means "frames-per-second"; "pps" means "pictures-per-second".
23.9fps[24pps] is BD/DVD cinema, progressive or soft telecined, ripped from disc [note 1].
59.9fps[2-2-2-4[24pps]] is my best guess how my TV displays 23.9fps[24pps] [note 2].
24fps[24pps] is 23.9fps[24pps] forced to theater frame rate/running time [note 3].
60fps[60pps] is 24fps[24pps] with interframe synthesis via 2-to-5 mv interpolation [note 4].
120fps[120pps] is 24fps[24pps] with interframe synthesis via 1-to-5 mv interpolation [note 5].

[note 1] 24pps is what's seen in theaters [note 6]; DVDs/BDs slow that down by 0.1% [note 7].
[note 2] 2-2-2-4 pull-down by the TV (...by appearance, the TV doesn't disclose anything).
[note 3] Force timebase & presentation time stamps via ffmpeg 'settb=expr=1/24,setpts=expr=N'.
[note 4] Motion vector interpolation synthesizes interframes & interframe pictures.
[note 5] Even better interframe synthesis due to integer (i.e. 5x, not 2.5x) interpolation.
[note 6] "Better" theaters triple-shutter to 72fps[24pps] but the picture rate remains 24pps.
[note 7] Slowdown: 24fps-to-24/1.001fps (so video can be telecined to NTSC 29.9fps ...yuck).

My Sharp 2K-TV,
1, Converts 23.9fps[24pps] inputs to 59.9fps[2-2-2-4[24pps]] display -- creates telecine judder;
2, Smooths (fuzzes) 59.9fps[2-3[24pps]] inputs -- less telecine judder but creates combing;
3, Displays 60fps[60pps] incredibly smoothly -- no judder, no combing;
4, Apparently drops alternate frames (120fps -> 60fps) without damaging the TV.

What does your TV do? How can you discover what your TV does? What's 'best' for all TVs?

[FranceBB]

What does your TV do?

Hi-end Samsung TVs from 2009 onwards do the following:

Input: 23.976p -> Linear Interpolation to 48fps + blending to 60p

Input: 29.970 telecined with 3:2 pulldown -> detects the telecine -> IVTC to 23.976p -> Linear Interpolation to 48fps + blending to 60p

Input: 29.970i (truly interlaced like for sports) -> bob to 60p

Input: 29.970p -> Linear Interpolation to 60p

Any other framerate set in between result in the TV not understanding what's going on and just leaving things as they are. For instance if you were to transmit a signal with let's say 28fps, it will display it as it is, resulting in stuttering etc.

What about 25p then? Well, if the TV is set to 60Hz, it doesn't detect it and just outputs the same, however if the TV is set to 50Hz it detects it and performs linear interpolation to 50p.

A note about linear interpolation: I've noticed that linear interpolation is quite good, but there are some artifacts, however those are limited. What I think happens underneath is that when the TV just doesn't know, it performs blending instead of linear interpolation, hence trying to limit the times in which linear interpolation results in artifacts.

Of course, the vast majority of contents I watch are PAL 'cause I live in PAL land and the TV is set to 50Hz, therefore what happens is that I always receive a 25i signal, but while for sports it's a real 25i signal that has to be bobbed to 50p and then displayed (and the TV does just that), for movies and TV Series it's actually a 25p flagged as 25i, therefore the TV detects that it's actually progressive and treats it as progressive (i.e it applies linear interpolation to 50p). There have been just a few times in which this didn't work out: you see, even though the content might be progressive, sometimes there are messages in a ticker showing up in the lower part of the screen and those messages are of course interlaced 'cause the whole stream is supposed to be interlaced, so what happens is that sometimes the TV detects it, switches to bobbing mode and you see the text moving fine but the whole scene stutter ('cause now you have those frames duplicated), and sometimes it doesn't and it keeps treating it as progressive and you see the text in the lower part of the screen being displayed as an interlaced mess.

[wonkey_monkey]

When you say "linear interpolation" are you talking about "smooth motion" settings and such? I.e. things no sane person would turn on in the first place? ;)

Input: 23.976p -> Linear Interpolation to 48fps + blending to 60p

That just sounds like the worst of both worlds...

[markfilipak]

When you say "linear interpolation" are you talking about "smooth motion" settings and such? I.e. things no sane person would turn on in the first place? ;)

That just sounds like the worst of both worlds...
@wonkey_monkey,

I'm with you. FranceBB can't mean motion vector interpolation because, if the TV is doing the decoding -- doubtful but possible -- then inside the TV at that point there's raw frames. Either that or, if the input is from a player or computer over HDMI or DisplayPort, then the TV's input is definitely raw frames. So, FranceBB must mean pixel interpolation (or maybe, just frame doubling) to 47.9fps and then 2-3 telecine to 59.9fps -- Is that right, FranceBB?

My Sharp has "smooth motion" and it's awful. I turned it off the first time I powered it up.

[markfilipak]

Hi-end Samsung TVs from 2009 onwards do the following:

Input: 23.976p -> Linear Interpolation to 48fps + blending to 60p

Input: 29.970 telecined with 3:2 pulldown -> detects the telecine -> IVTC to 23.976p -> Linear Interpolation to 48fps + blending to 60p
Blending? Really?

Input: 29.970i (truly interlaced like for sports) -> bob to 60p
Try this: separate the 29.9fps[59.9sps] fields to make two, 29.9fps[29.9pps] half-picture streams -- it doesn't matter whether the source stream is TFF or BFF -- then motion vector interpolate each half-picture stream separately to 119.8fps[119.8pps] (that's 4x), then delay the 2nd stream by 2 frames, then bob the first 2 frames of the 1st stream and weave the 2 streams together to form full-sized, 119.8fps[119.8pps] (progressive) frames. The 2nd half-picture stream delay is to time-align it's first frame (which is an original frame) with the 3rd frame of the 1st half-picture stream (which is a synthesized frame that coincides in time). Thereafter, each original field (top or bottom) will pair with a synthesized, time-aligned field (bottom or top) The result is seemingly 'live' -- like you're viewing reality -- and makes bob look absolutely 'mushy'. You can leave the result as 119.8fps[119.8pps] or drop it to 59.9fps[59.9pps].

Input: 29.970p -> Linear Interpolation to 60p
May I ask: For any of the above, how do you know that's what the TV does? Does it tell you? My TV tells me nothing and the manual tells me next to nothing (and in unknown, bogus marketing terms).

Any other framerate set in between result in the TV not understanding what's going on and just leaving things as they are. For instance if you were to transmit a signal with let's say 28fps, it will display it as it is, resulting in stuttering etc.
Well, 28fps that actually displays at 28fps will not stutter, so your TV must be doing some sort of telecine.

What about 25p then? Well, if the TV is set to 60Hz, it doesn't detect it and just outputs the same, however if the TV is set to 50Hz it detects it and performs linear interpolation to 50p.

A note about linear interpolation: I've noticed that linear interpolation is quite good, but there are some artifacts ...
Can you describe the artifacts? Are they background "drag" along the boundary of motion objects in panning shots? -- looks like the bow wave and wake of a boat viewed from overhead. That's what I sometimes get with real-time motion interpolation when the interpolator doesn't have enough time. Or by "artifacts" do you mean aliasing? Or maybe pixel twitter -- like sparkling?

The reason I'm so interested is that I'm considering buying a new TV and the marketing material just doesn't reveal what TVs actually do.

Thanks for your contribution and your thoughts and feel free to clarify or ask questions.

--Mark.

[markfilipak]

http://tiny.cc/cx02hz

You're a pro! Well, try the field trick I outlined using a real-time interpolator (maybe, SVP) and see what you get. I've found that, for the same codec, the field trick results in a stream that not only looks fantastic, but it's 1/6 to 1/8 the size (6x to 8x the bps) even for placebo transcodes. I was greatly surprised and amazed to say the least!