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Discussion Starter · #1 ·
I may eventually get a G150CLZ, which has a DVI input (I assume DVI-D). Before I go any further, I'd like to verify that the DVI spec is sufficient for 1365x1024 (actually, 1368x1024) at 60fps. 120fps may be better (it all depends on how in the heck I'm going to get an HTPC to play both film and non-film DVD content). There was a thread which said the DVI spec could only go up to 1280x1024. I suspect they were confusing it with DFP, though.


The Faroudja NRS+ apparently does not have any sort of DVI-out. A pity, as from what I've read, the NRS is the only video processor that even comes close to providing the kind of quality one can get from a lowly Celeron-based HTPC. The other models had some unspecified issues which made them clear 2nd-placers.


Still, since there seems to be NO way to feed a HTPC standard NTSC signals and have it process & scale them to 1365x1024 in realtime, I still have to keep looking for a video processor.


The Key Digital Leeza. According to what I read, it can handle up to 1366x768. So I'm guessing that model is out. Not that I was in a hurry to plunk down $5000 for it.


Anyone have any idea what that leaves? (Hint: For a free sheepish grin and roll of the eyes, you can recommend Teranex. :) )
 

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the new vigatec DUNE processor has a DVI output.
www.vigatec.de

it is not listed there yet but the specs of the legacy DUNE are

quite similar.
 

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Re: dvi


Single link dvi can handle up 1280x1024 (@85hz) or 1920x1080 (@60hz). Dual link dvi can handle 1920x1080 (@85hz) or 2048x1536 (@60hz). Not sure which cards use dual link tho.


See the following for more info:

http://www.ddwg.org/dvi.html


Re: ntsc


Have you tried dscaler?


Todd
 

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Quote:
Originally posted by Colmino
I may eventually get a G150CLZ, which has a DVI input (I assume DVI-D). Before I go any further, I'd like to verify that the DVI spec is sufficient for 1365x1024 (actually, 1368x1024) at 60fps. 120fps may be better (it all depends on how in the heck I'm going to get an HTPC to play both film and non-film DVD content).
Colmino,


What's the problem with playing film and non-film DVDs?


The software DVD players give you the option of switching the deinterlace scheme to be appropriate for both film and

non-film content. In fact, many detect the difference automatically.

Quote:


Still, since there seems to be NO way to feed a HTPC standard NTSC signals and have it process & scale them to 1365x1024 in realtime, I still have to keep looking for a video processor.
The above is not true - you install an NTSC video capture card and use dScaler software. Do a search on "dScaler" in

the HTPC forum.


You really have to do a better job of researching before you declare that no solution exists! [Try asking - not telling.]


Dr. Gregory Greenman

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Discussion Starter · #5 ·
> What's the problem with playing film and non-film DVDs?

> The software DVD players give you the option of switching the deinterlace scheme to be appropriate for both film and

non-film content. In fact, many detect the difference automatically.


Well, I don't have any such software right in front of me, but here is how I understand it: Film content plays at 24fps, and non-film content at 30fps (or 60; I guess it depends). (Not going to bother talking about PAL.) For a HTPC to display film content (24fps) without dropping / doubling frames OR performing a 3:2 pulldown, one's video card must be using a compliant refresh rate, such as 48Hz, and of course the software must be specifically capable of removing the 3:2 pulldown.


But then, using such a refresh rate suddenly makes any non-film content suffer the same compromises one was seeking to avoid for film content.


The obvious solution would be for both the projector and the software (and Windows for that matter) to not complain / choke from having the refresh rate constantly altered. And of course the DVD software would need to be able to detect which refresh rate is appropriate for the DVD content.


> Single link dvi can handle up 1280x1024 (@85hz) or 1920x1080 (@60hz). Dual link dvi can handle 1920x1080 (@85hz) or 2048x1536 (@60hz). Not sure which cards use dual link tho.


Ouch. For technology that seems to be in the infancy of its adoption process, those numbers sound regretably low. As in, three or four years before they start feeling out of date.


And they have me a little worried. If single link DVI can handle 1920x1080 @60hz, this _sounds_ like it should then be able to handle 1368x1024 at the same refresh rate (I'd be happy to know in advance if this is not the case). Is the DVI spec flexible? As in, could one take advantage of the unused bandwidth to do 1368x1024 at higher refresh rates?


The reason I ask is relevant to the HTPC thing about needing 48 or 96 (or 120) Hz output.


On the same subject, does anyone know if the G150CL has a dual link DVI input?


And while we're at it, does anyone know what PC card has a dual link DVI output? :)
 

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The web page referred to previously

http://www.ddwg.org/dvi.html


says that the maximum bandwidth of Single Link DVI is 165MHz. It goes on to give two example resolutions that meet that requirement---1280x1024 at 85Hz and 1920x1080 at 60Hz.


That obviously doesn't mean that DVI is limited to those two resolutions. DVI uses similar timing and sync criteria as analog displays do; the DVI spec, in fact, refers the reader to the VESA timing spec. So as long as the total bandwidth isn't exceeded, you can expect to support the same range of resolutions with DVI that you can with, say, a VESA compliant monitor. Since 1365x1024 at 75.1Hz fits well within a 165MHz bandwidth (in fact, it's somewhere around 150MHz) it should be fine.


Also, don't forget that with a digital display you don't need absurdly high refresh rates. The don't flicker in the same way that CRT displays do. I'd say there's no reason to go above 75.1Hz that I quoted above, which other posters have found is a sweet spot for the G15. But I'll bet that you can feed the D150CLZ a 48Hz refresh rate for film and 60Hz for video and it will do just fine---maybe even 24Hz for video.


So I'd say that Single Link DVI is sufficient for the D150CLZ.
 

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Discussion Starter · #7 ·
> So I'd say that Single Link DVI is sufficient for the D150CLZ.


Thanks a ton. This is exactly what I was hoping to hear.


Now I just need to figure out what HTPC users are doing about the 24fps / 60fps problem. (And figure out what Dscaler-compatible capture card has component-in.)
 

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Quote:
Originally posted by Colmino
> What's the problem with playing film and non-film DVDs?

> The software DVD players give you the option of switching the deinterlace scheme to be appropriate for both film and

non-film content. In fact, many detect the difference automatically.


Well, I don't have any such software right in front of me, but here is how I understand it: Film content plays at 24fps, and non-film content at 30fps (or 60; I guess it depends). (Not going to bother talking about PAL.) For a HTPC to display film content (24fps) without dropping / doubling frames OR performing a 3:2 pulldown, one's video card must be using a compliant refresh rate, such as 48Hz, and of course the software must be specifically capable of removing the 3:2 pulldown.


But then, using such a refresh rate suddenly makes any non-film content suffer the same compromises one was seeking to avoid for film content.


The obvious solution would be for both the projector and the software (and Windows for that matter) to not complain / choke from having the refresh rate constantly altered. And of course the DVD software would need to be able to detect which refresh rate is appropriate for the DVD content.
Colmino,


NO - NO - NO


Your "understanding" is in error - that's NOT how DVDs work.


BOTH film and non-film material is played at an effective framing rate of 30 fps.


The process of telecine is done BEFORE the data is written on DVD. Your software has NO CHOICE but to deal properly

with 3:2 pulldown!


Regardless of the origin of the material, film or video; the output of the MPEG decoder will have an effective framing

rate of 30 fps.


What software DVD player are you going to use for your HTPC? WinDVD? PowerDVD? Raviscent?


Well they all know how to deal with film material and telecine.


Your HTPC will not be changing refresh rates on the fly as it plays different material. You will use Powerstrip on

startup to define the resolution and refresh rate that is appropriate for your projector - and then EVERYTHING uses

that resolution and refresh rate from then on. There's no changing refresh rates depending on what the source of the

material on the DVD is.


I would suggest that you check out the HTPC forum and learn how HTPCs work before you waste any more of your time on

non-issues.


Dr. Gregory Greenman

Physicist
 

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The HTPC handles film content beautifully with 3:2 pulldown and for all intents and purposes, is displaying the same thing as 24 fps film. It is video that sometimes gives it trouble, as the deinterlacing methods in software DVD players are not as sophisticated as say, Faroudja. DScaler running GreedyHM can eliminate much of this problem.


There really aren't any component in video cards for DScaler. The top of the line is buying a modified Zoltrix card from KBK.


Try reading around the HTPC forum a little before spouting off all this :)
 

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Discussion Starter · #10 ·
> NO - NO - NO


Thanks for clearing that up.


> The process of telecine is done BEFORE the data is written on DVD. Your software has NO CHOICE but to deal properly with 3:2 pulldown!


I have been told that DVD playback software can remove the 3:2 pulldown, thereby effectively converting the video into 720x480p @24fps. This seems rather clear-cut, as does the idea that 720x480p @24fps displayed at 24 (or 48) Hz should look smoother than displaying one frame three times, next frame two times, 3, 2, 3, 2, etc. at 60 Hz.


> Your HTPC will not be changing refresh rates on the fly as it plays different material. You will use Powerstrip on startup to define the resolution and refresh rate that is appropriate for your projector - and then EVERYTHING uses that resolution and refresh rate from then on. There's no changing refresh rates depending on what the source of the material on the DVD is.


This isn't really quite how it's going to work. I refer you to this thread, where people were discussing one aspect of the reasoning behind this particular pursuit of mine:

http://www.avsforum.com/avs-vb/showt...hreadid=117547


In a nutshell: Possible methods for achieving on-the-fly, application-specific resolution alterations are discussed.


> The HTPC handles film content beautifully with 3:2 pulldown and for all intents and purposes, is displaying the same thing as 24 fps film.


Again, 3,2,3,2 is a visual eyesore compared to 2,2,2,2.
 

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Quote:
Originally posted by Colmino
> NO - NO - NO


Thanks for clearing that up.


> The process of telecine is done BEFORE the data is written on DVD. Your software has NO CHOICE but to deal properly with 3:2 pulldown!


I have been told that DVD playback software can remove the 3:2 pulldown, thereby effectively converting the video into 720x480p @24fps. This seems rather clear-cut, as does the idea that 720x480p @24fps displayed at 24 (or 48) Hz should look smoother than displaying one frame three times, next frame two times, 3, 2, 3, 2, etc. at 60 Hz.


> Your HTPC will not be changing refresh rates on the fly as it plays different material. You will use Powerstrip on startup to define the resolution and refresh rate that is appropriate for your projector - and then EVERYTHING uses that resolution and refresh rate from then on. There's no changing refresh rates depending on what the source of the material on the DVD is.


This isn't really quite how it's going to work. I refer you to this thread, where people were discussing one aspect of the reasoning behind this particular pursuit of mine:

http://www.avsforum.com/avs-vb/showt...hreadid=117547


In a nutshell: Possible methods for achieving on-the-fly, application-specific resolution alterations are discussed.


> The HTPC handles film content beautifully with 3:2 pulldown and for all intents and purposes, is displaying the same thing as 24 fps film.


Again, 3,2,3,2 is a visual eyesore compared to 2,2,2,2.
Colmino,


Yes - you can have the software remove the extra frames to get you a 24 fps framing rate which can be tripled to 72 fps

for projection.


But the only reason you do that is when you have a CRT projector. The CRT is subject to "flicker" - and you

increase the refresh rate on the CRT so that it doesn't flicker.


Since a CRT is "painting" the image with an electron beam - as soon as the electron beam moves on - the light emission

from the phosphor begins to decay. It is advantageous to refresh the image on the screen at a faster rate. But how

do you do that? If you double scanned a 60 Hz image rate, the CRT projector would have to be able to do a 120 Hz

refresh rate. This would be greater than the bandwidth of all but the most outrageously expensive projectors.


Therefore, the CRT owner has the HTPC delete the extra frames to get back to the native 24 fps - which is then

tripled to get a 72 fps rate - which most CRT projectors can handle.


Digital projectors don't work that way. They "lock and hold" the image.


A digital projector doesn't have this "flicker" problem. When the digital chip gets the image data for a given pixel,

it "locks" that in - and keeps displaying that data until it is updated with new data.


Additionally, there is a limit to how fast these chips work. For example, the response time of the JVC D-ILA chip is 16 ms.

Therefore, the D-ILA chip will only accept 60 refreshes per second.


Since you are considering feeding this 72 Hz signal to a JVC G150CL, if I understand your latest choice of projector to

be; then you are wasting your time trying to take a 60 Hz signal from the DVD, convert that to 72 Hz in an HTPC; only

to have the projector "throw away" the extra 12 frames per second because it can't update any faster.


If you have a G150CL, when all is said and done - the refresh rate WILL BE 60 Hz. That's what digital projectors do.


Like I said - take some time to learn the hows and whys of what you are attempting to do.


Dr. Gregory Greenman

Physicist
 

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Discussion Starter · #12 ·
> Like I said - take some time to learn the hows and whys of what you are attempting to do.


Part of the learning process, when it comes to forums or similar research, is obtaining at least two opinions and making sure the information is generally accepted to be correct. Case in point:


> Yes - you can have the software remove the extra frames to get you a 24 fps framing rate which can be tripled to 72 fps for projection.

> Since you are considering feeding this 72 Hz signal to a JVC G150CL, if I understand your latest choice of projector to be; then you are wasting your time trying to take a 60 Hz signal from the DVD, convert that to 72 Hz in an HTPC; only to have the projector "throw away" the extra 12 frames per second because it can't update any faster.

> If you have a G150CL, when all is said and done - the refresh rate WILL BE 60 Hz. That's what digital projectors do.


I had read that the G150CL was capable of refresh rates other than 60Hz. It never really was my intention to send it a 72Hz signal (you quoted me but perhaps didn't see it), but a 24 or 48 Hz signal, yes, as long as the HTPC could go that low.


What you're telling me about the G150CL, if you are in fact saying that the 60 Hz refresh rate is totally inflexible, conflicts with what I had originally read. It's good to see conflicting data because it at least means I won't stumble into this project with a potentially disastrous misconception, but now I have two answers, and it's not clear which may be accurate.


Thanks for taking the time to explain things.
 

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Quote:
Originally posted by Colmino



I had read that the G150CL was capable of refresh rates other than 60Hz. It never really was my intention to send it a 72Hz signal (you quoted me but perhaps didn't see it), but a 24 or 48 Hz signal, yes, as long as the HTPC could go that low.


What you're telling me about the G150CL, if you are in fact saying that the 60 Hz refresh rate is totally inflexible, conflicts with what I had originally read. It's good to see conflicting data because it at least means I won't stumble into this project with a potentially disastrous misconception, but now I have two answers, and it's not clear which may be accurate.
Colmino,


You have to be careful about what the spec actually means.


The specs you have been reading are what the JVC "accepts".


What it "does" is another matter.


Go to:

http://www.jvcdig.com/technology.htm#whitepapers


and get the white paper "D-ILA Technology..." by Dr. W. P. Bleha


On page 5, you will find the following statement on the temporal response time of the D-ILA chip:


"The D-ILA device has a true video-rate response time (the rise time plus fall time equals less than 16 milliseconds).

The temporal response curve is shown in Figure 6."


Later, on page 7, Dr. Bleha addresses the vertical scanning frequency:


"Vertical frequencies of 50 to 78 Hz are accomodated. The D-ILA is addressed at double the vertical frequency of the

input signal. However, the liquid crystal responds at the rate shown in Figure 6."


As per the above - the D-ILA can be fed, or can synch to; vertical scan frequencies from 50 Hz to 78 Hz. The chip is

addressed at double the scan rate - which would be 100 Hz to 156 Hz. However the chip responds at the rate given in

Figure 6 - which is 16 milliseconds. The inverse of 16 milliseconds is about 60 Hz.


As the paper states on page 5, the response time is determined by the thickness of the liquid crystal layer in

the chip. Since this thickness is fixed - so is the response time of the D-ILA chip.


Dr. Gregory Greenman

Physicist
 

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Greg,


Please see my post in the other thread. The D-ILA does not internally convert to 60Hz. If it did, then it would display 3/2 judder when fed both 60Hz and 72Hz.


I see 3/2 judder with a 60Hz input rate but not with a 72Hz input rate. The only explanation for this is that 60Hz is not an internal limit for driving the panels.


The 16ms response time limits the frame rate of the projector to 60fps. This is irrelevant when dealing with a 24fps source like film. You are confusing the refresh rate with the frame rate.


Colmino is correct that an HTPC refresh rate of 48Hz or 72Hz is ideal for film-based DVD's and a refresh rate of 60Hz is ideal for video-based DVD's. Any other rate adds judder so you would lose the liquid-smooth motion that a perfect multiple of the source rate gives you. The lowest common multiple of 24 and 60 is 120Hz, which is beyond the capability of most projectors.


Most people stick with 48Hz or 72Hz and live with the judder of video DVDs (since video DVDs are more rare and generally of lower quality than film-based DVD's).


Cheers,

Dave.
 

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Discussion Starter · #15 ·
> I see 3/2 judder with a 60Hz input rate but not with a 72Hz input rate. The only explanation for this is that 60Hz is not an internal limit for driving the panels.


It's uncanny how real-life tests have the potential for uncovering holes in spec sheets and logical assumptions.


I am interested to know if you've been able to confirm that it can handle the 72Hz input rate at "full panel" resolution (which I will admit is a term currently suffering from looseness of definition; it could mean 1360x1024, 1365x1024, 1366x1024 or 1368x1024, depending on whom one asks).


And if possible, I'd like to know whether or not such a rate / resolution would be beyond the capability of single-link DVI (assuming that's all the G150CL accepts). My calculator says no problem. But that's probably not a good way to judge.


> Most people stick with 48Hz or 72Hz and live with the judder of video DVDs (since video DVDs are more rare and generally of lower quality than film-based DVD's).


I intend to pursue a refresh rate-modifying option, which is a subject often discussed in the HTPC forum. Not specifically for the sake of video DVDs, but rather for PC-originated, non-DVD video, such as DivX encodes. (Don't jump to a conclusion, btw. There are legitimate uses for DivX, and it so happens that most of mine are of the variety comparable to everyday VCR usage.) The judder introduced with 3:2 pulldown is at least moderately subtle (3,2,3,2...). Judder from 60->72Hz? 2:1:1:1:1:2:1:1:1:1... It's the same rate of judder, but since the original frame rate is higher, the compromise to the fluidity of the video would be far more perceptible.
 

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Hi Colmino,


Yes, you can drive a pixel perfect full panel resolution at 72Hz. There's a simple explanation for the different resolutions you see quoted. The D-ILA is 1365x1024 but video cards only support custom resolutions in multiples of eight pixels, so you can go with 1360x1024 with five unused columns or 1368x1024 with an overscan of three columns.


We won't know about 1365x1024 over DVI until someone tries it. Even if it's not supported out-of-the-box it might be possible with a mod.


Cheers,

Dave.
 

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Discussion Starter · #17 ·
> There's a simple explanation for the different resolutions you see quoted. The D-ILA is 1365x1024 but video cards only support custom resolutions in multiples of eight pixels, so you can go with 1360x1024 with five unused columns or 1368x1024 with an overscan of three columns.


That's a pity. I suppose in theory, one could send 1368x1024 video to the D-ILA with three columns intentionally masked, and the video properly scaled to fit the remaining 1365... Hard to say what the D-ILA would do with such a signal. My guess is it would be brainless and downscale it internally, which would be pretty bad.


Plus I haven't the foggiest idea how one would go about getting their HTPC to do this.


Losing five columns is something I don't think I could accept, so I'll be trying to nail down a way to avoid that. The Faroudja NRS+ also only outputs 1360x1024.


> We won't know about 1365x1024 over DVI until someone tries it.


Well, single-link DVI can handle 1920x1080 at 60Hz, or 1280x1024 at 85Hz, according to what I've read. The math suggests that 1368x1024 at 72Hz is safely within limits. So now it's up to the capability of the spec. Since DVI is (reportedly) flexible enough to handle a strange resolution like 1365x1024 in the first place, I am cautiously hopeful.
 

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Colmino, if you really think you could see or benefit from using those 5 extra columns of pixels, then you have far better eyes than I do! :)
 

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Colmino,


I run at 1360x1024 "pixel perfect". I don't miss the five pixels at all, and indeed, can not even notice them.


Five pixels represents only three-tenths of one percent of the screen width, and on my set-up, I'm sure I have at least a few pixels of overscan falling on the masking around the screen.


Mark Hunter
 

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Discussion Starter · #20 ·
> Colmino, if you really think you could see or benefit from using those 5 extra columns of pixels, then you have far better eyes than I do! :)


Well, it's not that I could necessarily tell the difference between 1360x1024 and 1365x1024, as far as the PQ gain from the extra five columns go. It's that for an HTPC, the resolution of choice is 1360x1024. Pixel-perfect to a D-ILA, that leaves (I'm guessing) two columns on the left and three columns on the right, which would be black.


Fine, I could set up the screen / projector to display the image on a ~15.94 : 9 screen and not really discern the difference between that and true 16 : 9. But that's just for HTPC video. Let's say I use a Leeza, which can output 1365x1024 for full-panel pixel-perfect video. Suddenly the left and right sides of the screen are displaying out of bounds.


The alternative is to have non-HTPC video display at 16:9, and deal with thin black bars on the left and right sides of the screen when using the HTPC.


Of course it wouldn't be a ruinous compromise. But it would be annoying, like having a dead mirror in the dead center of the panel in a Marantz projector. I'd notice it every time.


The reason I seek solutions is because I figure they exist.
 
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