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PostPosted: Sun Jul 30, 2017 12:31 pm 
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rainwarrior wrote:
Or... are you talking about a TV that does output a picture that changes at 60fps by alternatingly updating the even and odd lines? (I don't believe I've ever encountered that in an LCD TV.)
Yes, that's what I'm saying.

tokumaru wrote:
If a sprite flickers, I get alternating scanlines with and without the sprite, with no visible changes from one target frame to the next.
You won't be able to tell the difference with a 30fps flicker:

Fields: A b C d E f (lowercase meaning the not-drawn flicker state)
30fps deinterlace: Ab Cd Ef
60fps deinterlace: Ab Cb Cd Ed Ef
In both cases you'll see an almost-identical comb-y result.

With a 1/3rd duty flicker (20Hz) the difference will be obvious:

Fields: A b c D e f G
30fps deinterlace: Ab cD ef - it will now appear to flicker at 10Hz
60fps deinterlace: Ab cb cD eD ef Gf - this will still flicker at 20Hz

rainwarrior wrote:
What about 120hz TVs?
I don't know how starting with a 60i source changes the motion prediction in a 120Hz TV. Certainly I can see that they'd interrelated, such as with mplayer's "mcdeint" deinterlacer which uses motion compensation to produce plausible lies for the missing scanlines, and the same motion compensation data would also be used to generate the entire missing frame for 120Hz rendering.


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PostPosted: Sun Jul 30, 2017 12:50 pm 
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tepples wrote:
What Brad wants is to take the 240p60 output of the emulated PPU, pretend it's field-based 480i60, and apply any of various deinterlacing filter chains to that.

I only really want a 30fps weave because that's the only one I've noticed HDTVs doing with 240p composite.

I only mentioned the possibility of configurable deinterlacing because it came up in discussion. I personally don't have any desire to simulate that kind of thing, only the one common mode that I have seen on many TVs.

Does anyone have an HDTV that does differently than this? I don't think Yadif is used in televisions. I have seen motion interpolation (yecch!) in some TVs, but not applied to the composite 480i input.

lidnariq wrote:
Fields: A b C d E f (lowercase meaning the not-drawn flicker state)
30fps deinterlace: Ab Cd Ef
60fps deinterlace: Ab Cb Cd Ed Ef
In both cases you'll see an almost-identical comb-y result.

Ah, yes that would be very difficult to see the difference between.

In my most often used LCD TV, I'm certain it's 30fps due to various tests I've done with it, but I don't think I would have been able to tell the difference in other cases I've seen.


Though, TBH either way is almost as good as the other for the kind of visual test I'd like to be able to do easily. Basically just want to be able to preview the negative impact of the weave on the image.


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PostPosted: Sun Jul 30, 2017 1:54 pm 
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rainwarrior wrote:
I only really want a 30fps weave because that's the only one I've noticed HDTVs doing with 240p composite.

My TV changes methods depending on the video. With no background scrolling, the TV's heuristic decides that the video was converted from 30p and matches pairs of fields to produce 30 frames per second. Once the background is scrolling, the TV's heuristic decides that the video is truly interlaced (with each field at a separate point in time) and switches to something more complicated that produces 60 frames per second.


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PostPosted: Thu Aug 03, 2017 12:49 pm 
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Many TVs will take a 15KHz signal and assume it is 480i. As a result, they will render the incoming lines into alternating fields. The changes may still be viewed at 60fps in total, but only every other line gets updated on every refresh. This is the worst-case scenario, in my opinion. Comb-like artifacts are seen on moving objects:

Image

Some TVs will weave these two into a full frame, updating the actual display only one two fields have been captured. This gives a 30fps effective refresh rate, where the resulting image is either a comb-artifacted blend of two frames (awful) or a 50% blend between two frames (semi-awful, old YouTube style). This mode is appropriate for interlaced video for which the source material was shot / composed at 30fps (e.g. Many television shows)

Some TVs will bob-deinterlace by only displaying the relevant field. This gets you a 60fps display with no comb lines, but it will wobble a bit (not the worst). This is the appropriate mode for interlaced video that is updating the source material at 60fps (e.g. Super Smash Bros Melee).

Finally, some TVs will treat 240p as only an even/odd field, and not try to deinterlace anything. This is ideal.


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