Question 60hz or 24hz for 4k movies

Well this is going to put the cat amongst the pigeons. Been playing with different settings and now have network 24p switched off and also the uhd Blu-ray 24p switched off. Now both Netflix and 4K disk playing show 2160p/60hz picture quality on both perfect no juddering, there was more juddering at 24hz. The other thing I find weird is that I now have a list of the 4k films on Netflix within the Netflix menu which I never had before.
 
Cheers Roku2 - still non the wiser about what the Projector is doing.

If you look at the TI site the projector manufacturer seems to be buggering around with an ‘old’ DMD chip to make it work with 4K signals.

Joe
 
Well this is going to put the cat amongst the pigeons. Been playing with different settings and now have network 24p switched off and also the uhd Blu-ray 24p switched off. Now both Netflix and 4K disk playing show 2160p/60hz picture quality on both perfect no juddering, there was more juddering at 24hz. The other thing I find weird is that I now have a list of the 4k films on Netflix within the Netflix menu which I never had before.
It might have put your pigeons out but it's not going to float many people's boats.

One man's perfect is another man's can't stand, but we are all entitled to what we see.

I would also want to check that my amp was not doing any video processing as that can also affect pq.
 
...or that you might have some form of motion smoothing engaged with 60Hz content.
 
After spending most of last night testing which was best between 25hz and 60hz by playing the same piece of video over and over again. 60hz won hands down zero juddering but 25hz had signs of judder, so a good result as far as I am concerned. Still can’t work out why the 4k list suddenly appeared in Netflix menu, it’s as if Netflix has just realised I have a 4k display.
 
After spending most of last night testing which was best between 25hz and 60hz by playing the same piece of video over and over again. 60hz won hands down zero juddering but 25hz had signs of judder, so a good result as far as I am concerned. Still can’t work out why the 4k list suddenly appeared in Netflix menu, it’s as if Netflix has just realised I have a 4k display.

25Hz is different again, sorry but I am not convinced your test methodology is up to scratch :(
 
NetFlix only streams content at it's native frame rate on certain platforms. On other platforms it's fixed at 60 Hz and frame rate conversion is used - 50 Hz (British / European) content looks particularly horrible.

While the latest editions of the Amazon Fire TV stick supports native frame rate, the NetFlix App running on the Amazon platform still does *not* support native frame rate. Amazon Prime Video (unsurprisingly) does.


Regards,
James.
 
Potentially yes. As others have said if you are moving from 24fps to 60fps then there is no nice multiple so you have to use something like 3:2 pulldown to do this

Three-two pull down - Wikipedia

Which incidentally means you need to adjust the sound to stop it getting out of sync.

If it was 30fps going to 60fps then you display two frames instead of just one.

3:2 pulldown doesn't adjust the sound to prevent going out of sync. 3:2 of 24 or 23.976fps fits into 60Hz or 59.94fps. These fit exactly.

Adjustments to sound typically only have to happen when the video clock and the audio clock aren't locked together (eg HTPC playback); or sometimes a pitch change when 24fps content has been mutated into 25 or 50fps (eg UK TV broadcast or PAL DVD of a 24fps movie).
 
3:2 pulldown doesn't adjust the sound to prevent going out of sync. 3:2 of 24 or 23.976fps fits into 60Hz or 59.94fps. These fit exactly.
Sorry it's late, how does that fit exactly?

Might want to edit the wiki page as that states the adjustment.

I realise there is a bigger adjustment from ntsc to pal etc.
 
Sorry it's late, how does that fit exactly?

Might want to edit the wiki page as that states the adjustment.

I realise there is a bigger adjustment from ntsc to pal etc.

Films on European broadcast television are sped up by a single frame to fit into the 50Hz signal, so go from being 24fps to 25fps, this changes the pitch of the audio and shortens the film's running time.

24 fps content into a 60Hz signal creates no shift in audio or running time. By using the uneven cadence of 2 frames, 3 frames, 2 frames and so on, 24 frames fit neatly into 60.
 
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Films on European broadcast television are sped up by a single frame to fit into the 50Hz signal, so go from being 24fps to 25fps, this chances the pitch of the audio and shortens the film's running time.

24 fps content into a 60Hz signal creates no shift in audio or running time. By using the uneven cadence of 2 frames, 3 frames, 2 frames and so on, 24 frames fit neatly into 60.
Thanks Ken, I realise that conversion to 25 Hz shortens the film not disagreeing there.

However what you have both said is there is no change due to pull down where as several sources including Wikipedia ( which is never wrong ;) ) have the audio changed on pull down. Albeit only 0.1% but enough so your lip sync is out by the end of the film.

Audio Pull-Down -0.1 % (NTSC)

Are you both suggesting this is wrong?
 
Thanks Ken, I realise that conversion to 25 Hz shortens the film not disagreeing there.

However what you have both said is there is no change due to pull down where as several sources including Wikipedia ( which is never wrong ;) ) have the audio changed on pull down. Albeit only 0.1% but enough so your lip sync is out by the end of the film.

Audio Pull-Down -0.1 % (NTSC)

Are you both suggesting this is wrong?

NTSC and PAL are analogue broadcast standards that have very little relevance in today's digital world - they are not synonyms for 60Hz & 50Hz. The way in which they delivered the image alongside the colour and audio components were much more convoluted than the simple stored frames and accompanying digital soundtracks of modern delivery methods. Put simply, it doesn't apply.
 
Sorry it's late, how does that fit exactly?

Might want to edit the wiki page as that states the adjustment.

I realise there is a bigger adjustment from ntsc to pal etc.
The wiki page is correct. You missed the bit at the beginning where it is converting 24fps to 29.97fps (different refresh rate family), for TV distribution. This is more complex than the pulldown you'd usually do at home.

As Ken says, it fits exactly.
If you perform 3:2 pulldown of 24fps content to 60fps it fits exactly, no audio adjustment required. (3*24+2*24)/2 = 60.
If you perform 3:2 pulldown of 23.976fps content to 59.94fps it fits exactly, no audio adjustment required. (3x23.976 + 2*23.976)/2 = 59.94fps.

The time when you have to put in place some sort of adjustment is when you are pulling down 24fps into 59.94fps, or 23.976fps into 60fps. The former the NTSC film adjustment discussed in the link you provide. But that isn't the case usually for folk doing the pulldown themselves in the home as as they usually have the option of both refresh rate groups, so you just choose the right multiple.

In the case where you don't have access to the correct refresh rates (some bits of hardware can't do one or the other of the groups) what more commonly happens in playback adjustment is a frame is dropped or added to sync the audio to the video. This is the cause of the frame stutter every 41seconds which is quite widely documented.

If you want to convert correctly between 23.976fps and 60fps or 24fps and 59.94fps then you would adjust the audio as described here:

However what you have both said is there is no change due to pull down where as several sources including Wikipedia ( which is never wrong ;) ) have the audio changed on pull down. Albeit only 0.1% but enough so your lip sync is out by the end of the film.

Audio Pull-Down -0.1 % (NTSC)

Are you both suggesting this is wrong?
No, it's not wrong. Your original post was wrong comparing 24fps and 60fps with 3:2 pulldown, saying that in that case there is an audio implication. Nothing need happen to the audio if that is truly the conversion you are doing. As explained the case where the adjustment happens to maintain sync (either dropping frames or audio adjustment) is 23.976fps to 60fps, or 24fps to 59.94fps.
 
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Thanks both makes sense.

So where I was coming from is that most of the Blu rays are encoded at 23.976 and I was being lazy not quoting that :)

Most monitors and PJ I have come across do support the 59.94 and will report that, however some don't for some bizarre reason. If the OP and subsequent poster don't for some reason then you would a this minor issue.

Is Netflix 23.976 or 24?
 
Thanks both makes sense.

So where I was coming from is that most of the Blu rays are encoded at 23.976 and I was being lazy not quoting that :)

Most monitors and PJ I have come across do support the 59.94 and will report that, however some don't for some bizarre reason. If the OP and subsequent poster don't for some reason then you would a this minor issue.

Is Netflix 23.976 or 24?
In those cases it would be very unlikely to get audio adjustment to fix it. It would almost always be dealt with by frames being dropped or duplicated. Some players might get out of sync if they don't have the ability to drop or add frames.

If you had an HTPC appropriately configured with something like ReClock it could be adjusting the audio to match the video.

If you check out the test streams title here:
Test Patterns | Netflix
You'll see Netflix have streams available at all of the various rates inc 24 and 23.976; Netflix server side itself is not a reason for the output rates not to be matched to the content framerate. It is down to the player to support the various options.
You can try playing each of the streams on a given Netflix player and observe the ouput formats. Different players will give different results depending on the hardware capabilities and the player middleware functionality.
 
The audio debate isn't really applicable to the original question, but it worth noting that the audio will stay locked with the video regardless of the actual playback speed (23.976, 24, 25 or 30) - but that doesn't mean the audio will retain its original pitch.

As discussed above, when 24p is shown on a 50 Hz system, it is sped up to 25p (25 * 2 = 50). There's no nastly pull-down that needs to be applied to the video, but it's running one frame per second faster than originally intended (but you can't see it). What you can notice is the raise in audio pitch.

Very (very) occasionally audio pitch correction is applied to bring the pitch back down to the proper level (even though the audio is still sped up).

Trivia: When Vangelis composed his score for BladeRunner in 1982, he was watching a 50 Hz video-telecine conversion on a monitor in his studio. So his orchestrations are actually slowed down (and pitched down) to match the 24 frames per second film. So if you want to hear the score as he heard it, you need to watch BladeRunner on a 50 Hz system.

There's really no practical reason for exclusive streaming services to not use native frame rate. But it's more complex for traditional broadcasters as the 50 Hz system is cast in stone for the UK / Europe. Can you imagine the BBC trying to explain to the general public why a film they watched on 'regular' TV had a shorter running time, to the version they streamed and watched on the same Tv? - I think for legacy reasons they're unlikely to change to adaptive frame rates. NetFlix on the other-hand, just need to pull their finger out and make it happen on all platforms!

Regards,
James.
 
Is Netflix 23.976 or 24?

If you check out the test streams title here:
Test Patterns | Netflix
You'll see Netflix have streams available at all of the various rates inc 24 and 23.976; Netflix server side itself is not a reason for the output rates not to be matched to the content framerate. It is down to the player to support the various options.
You can try playing each of the streams on a given Netflix player and observe the ouput formats. Different players will give different results depending on the hardware capabilities and the player middleware functionality.

To give you a very real example of the differences between players; if you play the 23.976 and 24fps Netflix test content on an AppleTV4K you will see they both end up being output at 23.976fps; same for 60 vs 59.94fps (both get output a 59.94fps). This means you'll either see a stutter every 41s on true 24/60fps content, and/or the audio will drift.

The Sony UBP-X800 player I also have in the same room with the same display correctly switches to 23.976 or 24fps depending on the content from Netflix.
 
This is one of the best topics I've read on this issue. I have both 4K firestick and 4K apple TV, Anthem Receiver and BenQ HT5550 projector. I always thought 60Hz was better than 24hz. I have been having issues with my 4k firestick and Apple 4K tv with my projector with strobing. It was driving me crazy. 4K firestick didn't happen as much as the apple TV, but Apple TV started flicking like mad as soon as I started to watch a movie set at 60hz. Once I made change in the apple 4K tv setting, I would see display 24hz and I thought - Dam, know I'm losing picture quality but the system isn't flickering anymore (strobe effect). I thought I was losing out on something. But after reading this and seeing that the movies are made in 24Hz and better for panning shots, I will leave it as it is.
 
This is one of the best topics I've read on this issue. I have both 4K firestick and 4K apple TV, Anthem Receiver and BenQ HT5550 projector. I always thought 60Hz was better than 24hz. I have been having issues with my 4k firestick and Apple 4K tv with my projector with strobing. It was driving me crazy. 4K firestick didn't happen as much as the apple TV, but Apple TV started flicking like mad as soon as I started to watch a movie set at 60hz. Once I made change in the apple 4K tv setting, I would see display 24hz and I thought - Dam, know I'm losing picture quality but the system isn't flickering anymore (strobe effect). I thought I was losing out on something. But after reading this and seeing that the movies are made in 24Hz and better for panning shots, I will leave it as it is.

You’re not losing picture quality If you set the display rate (Hz) to match the frame rate of the material (stream) - providing your streaming & display device can natively support 24 Hz. But it’s not always easy to tell what the correct setting should be.

99% of movies are shot and stored at 24 frames per second (or a very close fraction there-of). If you match your display rate (Hz) to the source material in frames per second (FPS) you’ll get less judder. This is most noticeable on slow panning shots - you won’t eliminate judder altogether (it’s inherent in 24 FPS), but that’s part of the filmic look.

However, NetFlix (and the Apple TV+ App when not used on an Apple TV device) don’t adapt to the native frame rate - they are always locked to 60 Hz output - in which case 60 Hz is the correct display rate to use.

This means that the frame rate has to be converted for the display device (24 FPS has to be made to fit in 60 Hz). What they actually do is turn 24 frames into 48 fields and repeat some fields 3 times rather than twice. It’s called 3:2 pull-down cadence.

This does unfortunately introduce extra judder and other unwanted motion defects which you can’t get rid of.

Also, be aware that traditional TV programmes are made in 30/60 (US/Canada), or for UK/Europe we use 25/50.

Typically, streaming devices made predominantly for the US market often forget about native support for 25/50 content and often convert it (badly) to 30/60. This looks absolutely horrible!

Amazon Prime content on (newer) FireTV Stick devices does adapt to the native frame rate of the content 😃, But NetFlix never does ☹.

I’m afraid it’s a minefield of frame rates and display rates out there and native FPS support isn’t really improving. NetFlix seem really stubborn about sticking only to 60 Hz output in their App.

Finally, the strobing you’re seeing may be a unique phenomenon to your projector, as it’s not a common side-effect of frame-rate to display-rate mismatching.

Hope this helps a little.

Regards,
James.
 
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You’re not losing picture quality If you set the display rate (Hz) to match the frame rate of the material (stream) - providing your streaming & display device can natively support 24 Hz. But it’s not always easy to tell what the correct setting should be.

99% of movies are shot and stored at 24 frames per second (or a very close fraction there-of). If you match your display rate (Hz) to the source material in frames per second (FPS) you’ll get less judder. This is most noticeable on slow panning shots - you won’t eliminate judder altogether (it’s inherent in 24 FPS), but that’s part of the filmic look.

However, NetFlix (and the Apple TV+ App when not used on an Apple TV device) don’t adapt to the native frame rate - they are always locked to 60 Hz output - in which case 60 Hz is the correct display rate to use.

This means that the frame rate has to be converted for the display device (24 FPS has to be made to fit in 60 Hz). What they actually do is turn 24 frames into 48 fields and repeat some fields 3 times rather than twice. It’s called 3:2 pull-down cadence.

This does unfortunately introduce extra judder and other unwanted motion defects which you can’t get rid of.

Also, be aware that traditional TV programmes are made in 30/60 (US/Canada), or for UK/Europe we use 25/50.

Typically, streaming devices made predominantly for the US market often forget about native support for 25/50 content and often convert it (badly) to 30/60. This looks absolutely horrible!

Amazon Prime content on (newer) FireTV Stick devices does adapt to the native frame rate of the content 😃, But NetFlix never does ☹.

I’m afraid it’s a minefield of frame rates and display rates out there and native FPS support isn’t really improving. NetFlix seem really stubborn about sticking only to 60 Hz output in their App.

Finally, the strobing you’re seeing may be a unique phenomenon to your projector, as it’s not a common side-effect of frame-rate to display-rate mismatching.

Hope this helps a little.

Regards,
James.

It’s extremely annoying that Netflix don’t output 24hz on the amazon 4k fire tv stick, Roku + stick used to but no longer do.
presumably an Apple TV 4K does but I hear there’s a lot of other issues with that at the moment ?.
How can it be so hard for a manufacturer to make deals and produce a streaming device that covers all the correct frame rates :facepalm:.
 
It’s extremely annoying that Netflix don’t output 24hz on the amazon 4k fire tv stick, Roku + stick used to but no longer do.
presumably an Apple TV 4K does but I hear there’s a lot of other issues with that at the moment ?.
How can it be so hard for a manufacturer to make deals and produce a streaming device that covers all the correct frame rates :facepalm:.

I really shouldn't be that hard. The SoC (System on a chip) used in the latest devices are all capable of adaptive frame rate and can trigger the display device to change refresh rates. The Amazon Fire TV stick can handle adaptive frame rate perfectly and does for Amazon's own content, but other App makers (NetFlix) just don't seem to think it's a priority which is really weird because they demand that programme makers use 24 FPS for NetFlix dramas, yet can't actually display is perfectly via their App.

No idea what Disney+ App stance will be... Hopefully they'll do it right.

Regards,
James.
 
I really shouldn't be that hard. The SoC (System on a chip) used in the latest devices are all capable of adaptive frame rate and can trigger the display device to change refresh rates. The Amazon Fire TV stick can handle adaptive frame rate perfectly and does for Amazon's own content, but other App makers (NetFlix) just don't seem to think it's a priority which is really weird because they demand that programme makers use 24 FPS for NetFlix dramas, yet can't actually display is perfectly via their App.

No idea what Disney+ App stance will be... Hopefully they'll do it right.

Regards,
James.
Disney+ and Netflix can do 24hz by running the add ons in Kodi on a Fire stick 4K. However, Dolby Vision is patchy on Netflix and I’ve not got working on Disney+ although it’s an option under settings in the add on. Just updated to latest stable Leia build so going to test Netflix shortly
 
P and hz are not the same thing. There is no 24p apart from maybe a watch.

Hz is how many times the image is refreshed a second.

P stands for progressive and is related to how many lines of resolution are on your screen, p meaning all lines are refreshed at the same time rather than i where every second line is refreshed at a time.

I realize this is an old thread and so my input is probably of no consequence, but I would like to correct the above relating to the 'P stands for' etc...
it does indeed stand for 'progressive' but as the name suggests the screen is built from a 'progressive' scan built from top left to bottom right (albeit at very fast scanning rate) as opposed to ''Interlaced' which is built from 1st line at top then a skip on 2, then lines 3, 5 , 7, 9 etc and then back to top for lines 2, 4, 6, 8 etc for each frame. I think the reasons for interlaced scanning related to (in UK anyway) 25Hz flicker elimination, as one half of picture was shown at 25Hz followed by other half at 25Hz which gave an 'apparent' full screen scan of 50Hz (more pleasing to the eye)

Following on from this I still do not see why films are almost always shot at 24fps when now days much higher frame rates are available and more frames = more data = higher definition?

If 25Hz gave flicker to some, if not all years ago then how can 24Hz be ok?

Yes I know about the 'film look' and how a slight bit of blur in a moving shot looks more natural when shot at 24fps but in this digital age this could be added in post?

See link for info on scanning rates...
 

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