False.VGA does not support interlaced formats.
None of the above.Are you talking about 480i (NTSC)? 576i (PAL)? 720i (barely used) or 1080i (FULL HD, used in broadcast video)?
Mmm, yeah. I've seen that. It's probably not useful for VGA, that's a television signal. That diagram is missing at least one crucial detail that differentiates VGA interlaced scan signals from television. Read on.Ok - its a new one to me.
But with a little bit of google - you could easily have found out what all this meant:
EG: **broken link removed**
That's okay. Hopefully this thread will clear up any confusion you have. Read on.Some confusion here.
Stick to computer monitors. Don't go into television standards please. And no, there's a bit more to it.VGA does have interlaced modes although in it's 30 or so years of existence I don't think I've ever seen it used. VGA is a computer display mode.
576, 720 and 1080 interlaced and progressive scan modes are for broadcast television video and CCTV.
There is some overlap and scan conversions between the two systems but they are basically intended for different purposes.
That's the basic idea but lacks important details for implementation.To make a signal 'interlace' add half a line scan to one field and remove half a line from the other. In systems with composite sync it is necessary to add equalizing pulses to prepare the timebases but in VGA where the syncs are carried as an independent signal, it probably isn't necessary.
That's a TV signal. We are talking VGA signals here. Shifting by half a horizontal sync is the basic concept for interlace but on VGA signal there are some important implementation details, which the above explanation lacks. Read on.View attachment 137209
See slide 42.
http://www.slideshare.net/MadhumitaTamhane/black-and-white-tv-fundamentals
You will need to alternate between even and odd fields by displacing the horizontal sync half a line with respect to vertical sync.
The reading of your video ram will also need to account for both even and odd line data, as well as this half line displacement between even and odd fields.
If you don't do that you will see two superimposed images shifted by half a line.
I'd say you're wrong, but I have to take into account that your definition of "old" might differ from mine. As of the very last generation of CRT monitors, like the year 2000 SVGA monitor I have here, interlaced modes still work as intended.This is only going to work on very old analog crt monitors.
If by recent you mean an LCD monitor, then that would likely be true. If you read my OP you will see that we are talking strictly CRT here. So not really true, false.Warpspeed; said:Anything even remotely recent will just reject the signal completely, and you will get an on screen message something like "video format not recognised" and a blank screen.
True.The problem with VGA is there are so many different standards, dozens of them with widely varying field and line rates and resolution. The only way it can work is if a microprocessor measures up the incoming sync waveforms and goes to a lookup table to decide which VGA standard is incoming.
Then we should stick with standard interlaced modes. No need to invent anything yet. Read on.If your home made non standard interlaced VGA is not recognised in the lookup table, the monitor will just reject it and show an error message.
False.If you have maybe a thirty to thirty five year old completely analog crt monitor it might work.
I don't think that was meant to be a compliment. I'm not an expert, and I don't appreciate being trolled for asking about some obscure but very valid technical question.You are clearly the expert here
Well, if you don't care or don't want to learn then I can't think of a good intention for why you would be in my thread. In fact if you don't like learning then perhaps this forum is not a good place for you.as no one else seems to have ever heard of it, used it or care about it.
Depends on your definition of "support". There is learning being done here. What will be learned will be incorporated into the next project.Why are you trying to support this standard?
No I don't. I don't know exact timings to make it work, and I don't yet know the purpose of polarity on sync signals. This would be much easier to solve if I had a reasonably capable digital oscilloscope.Have to agree with Tricky Dickey.
If you already know all the correct answers why bother asking the question ?
Last time I needed something from an academic journal I had to go flirt with a librarian at my my college library. Since I've long graduated I don't have my student access to academic journal and paper subscriptions. I'd have to pay my alumni dues to have that, and I'm just too cheap, and some other things...I have realized long time ago that Google is just for first approach on a subject. Now, when I want trustworthy information and sometimes "difficult" to find (like this one), I use other sources e.g. known research magazines or books.
This might not be exactly what you are looking for, but it seems they at least talk about it: A new algorithm for interlaced to progressive scan conversion based on directional correlations and its IC design
I have used the ieee xplore digital library and google search with the key words "interlaced IEEE". There is much more information apparently.
Cool. Thanks.
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