One point I wanna get across and see if anyone else experienced this before:

When I watch Spider Man 3 Blu-ray on Sony 60Hz and 120Hz set at Circuit City. 60Hz panel was producing nice and steady frams with a little picture lag compare to the 120Hz. However, there was a problem with 120Hz TV displaying fast-moving action scene. The frames were pixalized, and wierd colors and shapes appearing.

This could be due to the source was only 30fps, and the 120Hz TV force it into 60fps by calculating and adding an extra frame in between each real frame. (base on the changes comparing the previous and next real frame), thus a pseudo frame. FYI, this method was once used by Sony or Toshiba's last generation TV and called it PictureFlow or sth.

While with slow moving scene, there was no problem, very very smooth.
However with fast-action scene, it might be possible that the image processor of the 120Hz display wasn't calculating fast enough to produce a proper pseudo frame so it produces an immature crappy frame.

This is only my assumption, I would like to have technical inputs from the experts.

PS. are blu-ray disks 30fps or 60fps?

One point I wanna get across and see if anyone else experienced this before:

When I watch Spider Man 3 Blu-ray on Sony 60Hz and 120Hz set at Circuit City. 60Hz panel was producing nice and steady frams with a little picture lag compare to the 120Hz. However, there was a problem with 120Hz TV displaying fast-moving action scene. The frames were pixalized, and wierd colors and shapes appearing.

This could be due to the source was only 30fps, and the 120Hz TV force it into 60fps by calculating and adding an extra frame in between each real frame. (base on the changes comparing the previous and next real frame), thus a pseudo frame. FYI, this method was once used by Sony or Toshiba's last generation TV and called it PictureFlow or sth.

While with slow moving scene, there was no problem, very very smooth.
However with fast-action scene, it might be possible that the image processor of the 120Hz display wasn't calculating fast enough to produce a proper pseudo frame so it produces an immature crappy frame.

This is only my assumption, I would like to have technical inputs from the experts.

PS. are blu-ray disks 30fps or 60fps?
In most case, neither. They're usually 24p since most of the content is films.

There's really no reason what you saw should be due to the scan rate of the monitor. Jitters maybe, but not the problems you saw. I would say that the issue was somewhere between the player and the TV - probably a bad cable.

At any rate, one thing that can occur is a TV may not truly scan at 120Hz. As a result, it conerts the material from 24fps, to 60fps, then doubles it to 120fps. That can be as bad or worse than simply using 3:2 pulldown to convert 24fps to 30fps.

The OP is describing what I've seen with some motion interpolation algorithms that are used on some, but not all, LCD panels (and not just 100/120Hz ones)

Some manufacturers are offering the option of interpolating new frames to increase the perceived frame rate of a low frame rate source.

In the UK, where we use 25p (rather than 24p) broadcast for film and stuff shot with a film look, some 50Hz displays converted the 25p source (deinterlaced from 50i 2:2) with frame interpolation, so rather than repeating each 25p frame twice, instead it in-betweened a new frame, but obviously at a consumer price point the processing power isn't there to do this properly in all cases, so on complex scenes the system falls to bits - particularly on fast movement. It also struggles to cope with compression artefacts.

They stick out a mile in showrooms - as everything on them looks like it was shot on tape at 50 or 60Hz interlaced or progressive - so looks like sport or an entertainment show, not a movie or drama. (Much more fluid motion - but also far more artefacts)

This technology was originally limited to just a few 50Hz panels (and in fact was also used on some of the high-end late-model 100i CRTs sold over here), but has become much more widespread with 100Hz displays (equivalent to US 120Hz models) Whether there is inbetweening from 24/30/60p to 120p (or from 25/50p to 100p) I don't know - but the 25->50p conversion is bad enough in the UK models.

Most devices allow you to switch this off and have frame repetition instead - but some models (some Panasonics and Samsungs) didn't when I last checked - making them close to unwatchable if you care about picture quality.

Was the 120Hz feature enabled on the 120Hz set?
As I understand the 120hz feature there are two possible benefits.
First when processing 60 frames per second souce it can create an additional interpolated frame betwen each pair of frames.
Secondly for 24fps movie they needs no cadence correction since 120 is an exact multiple of 24.

Was the 120Hz feature enabled on the 120Hz set?
As I understand the 120hz feature there are two possible benefits.
First when processing 60 frames per second souce it can create an additional interpolated frame betwen each pair of frames.
Secondly for 24fps movie they needs no cadence correction since 120 is an exact multiple of 24.

The latter is very desirable - allowing 5:5 rather than 3:2 - and symmetrical motion. However if there is interpolation going on in conversion of 24p to 120p - this isn't good news.

The former is definitely currently not desirable. Can anyone confirm whether 60Hz sources are interpolated to display at 1:1 120p rather than displaying the 60p (de-interlaced from 60i if required) at 120Hz using 2:2?

The latter is very desirable - allowing 5:5 rather than 3:2 - and symmetrical motion. However if there is interpolation going on in conversion of 24p to 120p - this isn't good news.

The former is definitely currently not desirable. Can anyone confirm whether 60Hz sources are interpolated to display at 1:1 120p rather than displaying the 60p (de-interlaced from 60i if required) at 120Hz using 2:2?

The explaination of interpolation does sounds like could it have been the culprit. I would assume yes the TV set that I saw in Circuit City must have the interpolation on.

Some users say the interpolation help them alot, less artifacts, less blur, less ghost images on a 120Hz set.

The former is definitely currently not desirable. Can anyone confirm whether 60Hz sources are interpolated to display at 1:1 120p rather than displaying the 60p (de-interlaced from 60i if required) at 120Hz using 2:2?

Would this depend on the particular model? Or all 120Hz panel are the same?

AFAIK the implemention of 120Hz varies by manuafacturer and also for some by model generation.

I just saw a report about sets using 240Hz next year.

This has to be just a marketing ploy, as I can see no benefit for this.

Yep.

There is a REAL reason to use up to 300fps for capture - as it will generate massively cleaner and clearer motion (it also has the byproduct of nicely working with 60 and 50Hz systems!).

Anyone who saw the BBC demos of sequences displayed at 100p at IBC (derived from 300p captures) compared with the same scenes at 50p and 25p will know how much clearer the whole frame becomes at 100p - particularly on motion, pans etc. They also showed some 300p stuff at 1/3rd speed (they haven't got a 300p capable display yet!) - and that was incredibly clear.

However 240Hz displays - like 120Hz ones - are still only being fed with 24p, 60i or 60p content - and interpolating 240 or 120Hz motion from this. The results are far less compelling...

24Hz sampling can cause real temporal aliasing issues - like the classic train wheels appearing to go backwards when captured at such a low frame rate. Interpolation of this stuff to 120 or 240Hz will just make the wheels appear to go backwards more smoothly. However if you captured at 120 or 240Hz, they will probably appear to go in the right direction!

There is a REAL reason to use up to 300fps for captureOk, but that is capture and it refers to FPS. How does FPS equate with Hz?
240 Hz is a LONG way from 24Hz, let alone 120 Hz. How much does one need? ;)

Ok, but that is capture and it refers to FPS. How does FPS equate with Hz?


Frames per second is the number of frames captured per second.

With a progressive capture based system then the number of frames captured per second is the number of images captured per second (it is NOT so straighforward with interlaced video)

The refresh rate of the display is the number of times the display updates - i.e. the maximum number of different images that can be displayed per second.

In the US - movie films are shot at 24fps. Blu-ray discs have a 1080/24p native recording of this (usually). If this Blu-ray is played on a 1080/60p display, that is refreshing at 60Hz (and not interpolating), then one 24p frame is displayed 3 times (for 3 x 60p frames) and the next 24p frames is displayed twice (for 2 x 60p frames)

If you have a 120Hz refresh rate display, then the 24p frames can each be shown 5 times ( for 5 x 120p frames) OR the 24p motion can be interpolated to 120p motion creating 4 new frames for every original frames (or 5 entirely new frames for each frame based on the original sequence)


240 Hz is a LONG way from 24Hz, let alone 120 Hz. How much does one need? ;)

It entirely depends on the quality you are prepared to put up with.

24fps capture was defined many years ago, ISTR when sound was added to movies?, as being JUST good enough. Every film frame costs money in stock and processing costs, so the fewer frames you shot per second the less it cost to shoot - thus shooting at 48fps, 60fps etc. was massively more expensive than shooting at 24fps (and would have reduced shooting time on each roll of film etc.)

For decent image capture - it sucks. You have to be very careful with panning speeds, and can't comfortably captured fast paced sports. Football, Tennis etc. on film looks horrible.

This is one reason why 60Hz capture (60fps for 720p and 60 fields per second for 1080i) is required for sports and we can't run networks at 1080/24p...

The BBC demo was to demonstrate that whilst we are investigating higher and higher resolutions for broadcast TV - HDTV, Super HiVision etc. - we also need to consider whether the current mix of 24/25p and 50/60p is going to be good enough as well.

Comparing 25p - where there was obvious temporal aliasing on motion (so you ended up with poor motion rendition on tracked objects, and an extremely juddery and motion blurry background) - to 50p - where the temporal aliasing was less (the wheels on the train went in the right direction) but a camera panning across a background left you with significant motion blur (though with less judder), to 100p - where the background on panning shots was much clearer and there was almost no judder on foreground or background motion.

The test scene was a simple model train layout. For one portion, the camera tracked the moving train, so it stayed in the same position in frame but the background was panned past quite quickly. The train wheels and the station signs in the background were two easy things to evaluate the quality differences between frame rates.

The suggestion was that for some fast moving stuff - if you want a really accurate "like being there and seeing it with your own eyes" clarity of experience, you may need to go to 300fps. They used jugglers as an example to clearly see the batons in mid-flight...

Understood, but all of that is only good if the source can provide it. This is the same deal that is with the HDMI 1.3 spec. Sounds good on paper, but the really isn't any material that can take advantage of the increased chroma bit rate.

What I was really referring to was this new crop of 120Hz LCD's starting last year, which have been reported in many tests as a mixed blessing. To some eyes, with certain material, it was a improvement, but with others, it made things worse.

Understood, but all of that is only good if the source can provide it. This is the same deal that is with the HDMI 1.3 spec. Sounds good on paper, but the really isn't any material that can take advantage of the increased chroma bit rate.


Yep - that is why the BBC - who are a big "source" (i.e. a large producer of content) are trying to trigger the debate, so we discuss this stuff before locking ourselves in to another format. When we're going for 16x HD resolution spatially, we should be considering temporal resolution as well (which has been the same since the 1930s in European TV terms - when 50Hz sampling was introduced with 405 line BBC TV in 1936)


What I was really referring to was this new crop of 120Hz LCD's starting last year, which have been reported in many tests as a mixed blessing. To some eyes, with certain material, it was a improvement, but with others, it made things worse.

Yep - the 100Hz models that have been on the market in Europe for a year or two are similarly mixed.

I find it ironic that many producers shoot SD content at 50i - and flicker it in post to give it a filmic 25p look, and then TV manufacturers create interpolation algorithms that remove the 25p film look and convert it back to 50Hz - or even 100Hz - motion! (But worse than the original because it is informed guesswork...)