Emulate interlaced display mode on your monitor

[Awatef]

I found a way to emulate it, by replacing the odd lines in the even fields with black and the even lines in odd fields with black, with a quite sophisticated method (useful for analog telecine NTSC sources and many PAL anime DVDs) resulting in a 50fps file for PAL and 60fps for NTSC.

Is there a filter that can make that directly with 50fps/60fps output?

The result is exactly as on TV using 640x480 resolution @ 120Hz with a 640x480 60fps file.
Only problem is: the lower part of the screnn is darker than the higher side. Is it my Ati rage 128 card or has everybody such a problem?
NB: In VirtualDub, the picture is normal.

[Guest]

I've experimented with this in the past. I found that the synchronization with the screen refresh is absent (obviously), so you get visible tearing. I also found that encoding it in DivX leads to seriously unacceptable results (try it!). The only codec I found that worked for me was the Panasonic DV codec. A subtle gray looks nicer than black, by the way.

I did it with a VirtualDub filter called "Fake". I could make it available if there was any interest.

[avih]

@Awatef:

i hope i understand you well. if i do, then clip.bob does exactly the same (without the black lines in-between, but on real tv you don't see black lines either). it does give 50/60 fps clip...

it just seems too trivial to me. did i understand u correctly?

[Guest]

Excuse me for answering since your post was exclusively addressed to Awatef. :)

When you bob you get flutter and shimmering. You don't see flutter and shimmering on an interlaced display. The idea is to simulate what happens on a real interlaced display. I doubt that it has any practical application, but it is fun to play with. It doesn't work very well anyway, because the phosphor characteristics of computer monitors are very different from those of TVs.

[avih]

no need for excuses ;)
i think that in order to emulate REAL interlaced display one would have to:

0. define the type of tv to emulate (i.e. standard interlaced, '100Hz', etc). i'm assumming 'standard' for the next sections.

1. separate fields (-> 50fps)

2. 'smart' resize each field (enlarge) while emulating the beam effect on the screen (high intensity in the center of the beam, and lower on it's edges). the resize factor should be at least 3, such that the beam will have a center and 2 edges. resize factor of 2 will require to have pixels which are overlapped by 2 scanlines. for better accuracy, i think that a factor of 4 should be used to have 2 pixels for center, and one pixel for each edge of the beam. an even factor will also make it easier for step 3.

3. offset even/odd fields vertically to match the original spatial location of the scanlines.

4. some kind of temporal smoother to match the one of a tv screen delay (if you REALLY have spare time to play with, it could be that the fade of the beam is dependant upon it's intensity or even other factors... but i don't really know the physics of tv screens).

and btw, some tv do shatter, especially with computer generated material (subtitles, station logos, etc). it really depends on the physical parameters of the display, and the technology that drives it.

but, this sure will be an excellent filter for real fun ;)

[Awatef]

@ neuron2
Can you please give me a link where to download that "fake" filter?

The idea behind it is to get motion and display quality as near as possible to TV on problematic sources, like analog telecine NTSC DVDs and most PAL anime DVDs, as well as pure interlaced sources.
It looks very good (and motion is perfect), but I'm just having the lower part of the screen darker than the higher part, and somehow, in 640x480 resolution, when I move the window up, the darker side gets smaller and smaller, so it gotta be a driver or monitor problem, right?!

Or is there a driver that can force my ati rage 128 card and/or my monitor (a compaq 17" display) to make interlaced scan?

I remember many years ago, I got an IBM 14" display and some cirrus VGA card, and there was an option: 1024x768 interlaced!