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Discussion Starter · #1 ·
I gather that 1080p isnt going to happen with this projector. I was wondering what res / refresh would look best for dvd material, and hdtv viewing. I know that this is a subjective question, but I figure that I can get some opinions. I am trying to find a good resolution to configure my PJ for. I already have it throwing a picture of 1024x768 @ 60hz.


I currently have no other suitable method for driving the projector, and I am confident in my skills with computers (its a living).


I am very comfortable with my htpc, and its running linux, and was originally used with an SD Sony wega, so its time to retool it. I am not using powerstrip or TT (windows apps).


Thanks.
 

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I have a 9PG+ also, with HTPC and other sources.


You could probably push it to 720P at 72 Hz, and would get the best (i.e. minimal) judder with motion playback. Do you have a Linux player that gives you some flexiblity with regards to chosen refresh rates? Or will work with whatever you have the desktop setup for? If so, 1280X720 at 72 Hz ought to work OK.


For me, de-interlacing performance with video source material or mixed material or incorrectly flagged material is important, as well as film source DVD and HD playback, so I use an ISS-6010 switcher, and go between the 1080i RGBHV output from my MyHD card (Windows, of course), using AnyDVD to allow playback of any DVD on the MyHD, and also use a DVP971 DVI output scaling player with a Dtronics DVI-D to RGBHV converter box. Every now and then I try one of the software players on the nVidia 6600 card I'm running, but can't generally make a case for that approach. HTPC hardware is an ATC HTPC case, with AMD64 PR3700.


I'm pretty happy with how those look on my PG, and looking forward to getting my 10PG installed and getting a bit of a resolution and brightness upgrade.


What kind of options are available for Linux? I think there is also a dedicated chat area for Linux HTPCs, you'll probably get more useful inputs than from WinAMD guys like me. ;)


~Jon
 

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Jon's go the right idea. 720p at 71.928Hz (to be exact). Use Powerstrip to achieve this.


Horizontally, 1440 is nice as it's exactly double of the DVD resolution.


So [email protected] is what I would try on this PJ (and most other 8" EM focussed PJ's). Someone people will tell you it's a 7" or 7.5" PJ, but the tubes are the same size as other 8" PJ's.


If you set up the PJ well, 720p should provide you with just visible scanlines on an average (7-8' wide) 16x9 screen.


If you can't see scan lines at all (with only the green tube on) then try lowering the vertical resolution to maybe 600p or so and see if it looks any better. If not, live with 720p.



If you're running a 4x3 screen the you may want to consider [email protected]



Kal
 

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Quote:
Originally Posted by kal
If you're running a 4x3 screen the you may want to consider [email protected]



Kal
I have the 9pgx, and it looks pretty sweet at that res - don't have powerstrip, so using video card's timing, running at 60Hz, still looks nice enough that I have put off buying a new scaler.
 

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Discussion Starter · #5 ·
I will be watching 90% 16:9 / 1:2.35..


and the rest 4:3. So I assume that a 16:9 setup would be best for the raster setup.
 

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I have a NEC PG9+ that was retubed and setup at my house by Doug Baisey, the resident NEC guru here.

The pj is powered by an htpc with a 6600GT modded bt Mike Parker.

I run it at 1280x720 @ 60Hz.

The main reason was that the bandwidth for this res is close to 75Mhz if I am not mistaken and Doug has mentioned that this was close enough to the max bandwidth of the pj.


I have a 110" screen 16/9 and I really like it.

HD is quite insane with this setup. :)


Now, if somebody can show me that a little higher res would make a big difference, then I am all for trying... ;)


Arno
 

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Quote:
Originally Posted by kal
Jon's go the right idea. 720p at 71.928Hz (to be exact). Use Powerstrip to achieve this.


Horizontally, 1440 is nice as it's exactly double of the DVD resolution.


So [email protected] is what I would try on this PJ (and most other 8" EM focussed PJ's). Someone people will tell you it's a 7" or 7.5" PJ, but the tubes are the same size as other 8" PJ's.


If you set up the PJ well, 720p should provide you with just visible scanlines on an average (7-8' wide) 16x9 screen.


If you can't see scan lines at all (with only the green tube on) then try lowering the vertical resolution to maybe 600p or so and see if it looks any better. If not, live with 720p.



If you're running a 4x3 screen the you may want to consider [email protected]



Kal
1440x960 @72Hz requires a 150Mhz bandwidth. That would REALLY give you the SOFT "film like" look that some people talk about. The ONLY other person I've heard advocating that resolution besides you was Chris Wiggles......and I think he's taken one toke too many. :D
 

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Discussion Starter · #9 ·
I have a good clean 720P signal now, and I think its- a winner.. any reason to pun at a nonstandard resolution over 1280x720?
 

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Quote:
Originally Posted by Wardour
I have a good clean 720P signal now, and I think its- a winner.. any reason to pun at a nonstandard resolution over 1280x720?


NONE, IMHO. ;)
 

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Quote:
Originally Posted by techman707
1440x960 @72Hz requires a 150Mhz bandwidth. That would REALLY give you the SOFT "film like" look that some people talk about. The ONLY other person I've heard advocating that resolution besides you was Chris Wiggles......and I think he's taken one toke too many. :D
Actually, good point... yes, 150Mhz is too high. Best part of using an HTPC is that you can try just about anything and see... (for free).


Kal
 

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There’s one thing I don’t understand in these bandwidth discussions, and I don’t recall seeing it mentioned anywhere. Perhaps someone could tell me if I’ve got this completely wrong. I’m only concerned with regular DVDs here – not HD.


The DVDs are recorded at 720 pixels wide. The worst-case pattern to display would be alternating black and white vertical stripes one pixel wide. One black pixel, one white pixel, one black pixel, and so on. Thus the video for a single line would be a square wave with 720 “on/off†transitions.


If you are scaling to 1440 this would translate to two black pixels, two white pixels, two black pixels, and so on. Thus the video for a single line would be a square wave with 720 “on/off†transitions.


In other words, if you scoped the video signal you would see EXACTLY THE SAME waveform for 720 and 1440.


So – for regular DVDs – there is absolutely NO advantage in running anything other than 720 horizontal. In fact (except for 1440) there are disadvantages for other resolutions, such as 1280, as the scaling artefacts will lead to more than 720 “on/off†transitions in a single line and therefore require more bandwidth.


Am I right?
 

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I'd say you're mostly right, but alternating black and white stripes (much less color!) would be pushing the bandwidth limits anyway for a DVD signa. When you upscale, the scaler is doing interpolation, and ideally you'll like the dispaly to not be limiting the response rate to follow that signal. It especially becomes a problem when you're pushing higher frame rates (like 72Hz) and there's less time for each frame- this is more stess on the deflection electronics (requires higher voltages and currents in the yokes to get the faster sweep rates), and at some point things just don't keep up.


The 9PG+ produces a great picture as long as you don't ask unreasonable things of it. That's why I've got a 10PG on the floor waiting for me to have some time to set it up... I want to ask more unreasonable things of my system! ;)


~Jon


With any projector, some experimentation with sweep rates and resolutions is a good idea to see what produces the best picture qualityl, including resolution, motion judder, etc, while keeping convergence drift and HF roll off to reasonable levels.
 

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Quote:
Originally Posted by Chris Bigos
There’s one thing I don’t understand in these bandwidth discussions, and I don’t recall seeing it mentioned anywhere. Perhaps someone could tell me if I’ve got this completely wrong. I’m only concerned with regular DVDs here – not HD.


The DVDs are recorded at 720 pixels wide. The worst-case pattern to display would be alternating black and white vertical stripes one pixel wide. One black pixel, one white pixel, one black pixel, and so on. Thus the video for a single line would be a square wave with 720 “on/off†transitions.


If you are scaling to 1440 this would translate to two black pixels, two white pixels, two black pixels, and so on. Thus the video for a single line would be a square wave with 720 “on/off†transitions.


In other words, if you scoped the video signal you would see EXACTLY THE SAME waveform for 720 and 1440.


So – for regular DVDs – there is absolutely NO advantage in running anything other than 720 horizontal. In fact (except for 1440) there are disadvantages for other resolutions, such as 1280, as the scaling artefacts will lead to more than 720 “on/off†transitions in a single line and therefore require more bandwidth.


Am I right?
I guess all you Chirs' stick together? :D Chris Wiggles believes that 1440x960 should be used on EVERY projector, whether it can handle it or not. Personally, I don't see scaling artifacts using 1280x720.


If you want to run at the actual DVD resolution of 720x480 on a "decent" projector, you're going to see scan lines, which MORE than anything else, RUINS the very "film like" experience you're looking for.


You wouldn't be running those resolutions for PAL anyway.....which is what I assume you run, right?
 

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Jon,


I was just using b/w stripes as a worst case. I agree that would be pushing the limits – in fact, it IS the limit! I also agree with you about upscaling needing interpolation. Which I (in my ignorance) maintain is unnecessary. I just cannot see how the original 720 pixels on the DVD can be bettered. Using a horizontal resolution of 720 provides a 1:1 mapping. It will display 720 vertical b/w lines without any distortion at all (within the capabilities of the PJ, of course). I have a 6PG Xtra, BTW.


Upscaling to, say, 1280 doesn’t make things “better†by displaying more than 720 vertical lines. All it does is alter the widths of the lines to make them fit into 1280 pixels (i.e. interpolating) and thus distorts the picture! By necessity, some lines will be one pixel wide and some will be TWO pixels wide. Except for 1440 where all the lines once again become equal in width (two pixels). But this is no better than the original 720, so why bother?


This applies whatever the refresh rate or vertical resolution. The time taken to “write†a single horizontal line is in no way dependent on the number of pixels in that line. It is a factor of the refresh rate and the VERTICAL resolution.


Bruce,


Yes- I run PAL. I use a Momitsu at a resolution of 720 x 864. 720 for the reason stated above, and 864 because it’s a tidy 1.5 times the DVD vertical resolution (equivalent to 720 in NTSC-land). I understand what you say about scan lines, but that’s all to do with vertical resolution and nothing to do with horizontal resolution. If I ran at 1280 x 864 all I would be “gaining†is distortion of the vertical lines.


As I said in my original post, I’m more than happy to be corrected on this. I do not presume to know more than the experts on here. I know it’s the done thing to run with a horizontal res greater than a vertical res. But I have yet to see an explanation of how increasing the horizontal resolution above the native DVD’s 720 makes the picture any better. Someone educate me! :)
 

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Quote:
So – for regular DVDs – there is absolutely NO advantage in running anything other than 720 horizontal. In fact (except for 1440) there are disadvantages for other resolutions, such as 1280, as the scaling artefacts will lead to more than 720 “on/off†transitions in a single line and therefore require more bandwidth.


Am I right?
Nope. Resampling (upscaling) has been discussed enough times that I won't bother doing it again. The end conclusion is that the benefits of doing it, outweigh the distortion introduced by it.

Quote:
Upscaling to, say, 1280 doesn’t make things “better†by displaying more than 720 vertical lines. All it does is alter the widths of the lines to make them fit into 1280 pixels (i.e. interpolating) and thus distorts the picture! By necessity, some lines will be one pixel wide and some will be TWO pixels wide. Except for 1440 where all the lines once again become equal in width (two pixels). But this is no better than the original 720, so why bother?
Upscaling creates new picture information using the existing, hence interpolation. The effect you're talking about is called nearest neighbour resize and nobody uses that (guess why). Instead we use much better methods like bicubic (good), and Lanczos (best).


You should just try it for yourself. I personally wouldn't watch 720x480 on my 6PG.
 

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OK – so now I’m a bit more educated, at least on this topic. :D :D


Searched “Lanczos†and saw the light. I never had a problem with scaling, etc., vertically to get rid of scanlines, but I did have that mental stumbling block over doing it horizontally. The example I gave was fair enough as far as it went, but I should have been thinking in two dimensions and not just one.


Anyway, a lesson learned the hard way will be remembered. Thanks for the pointer. (Nice screenshot b.t.w.)
 

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Actually that makes me wonder what 720x720p would look like. No scanlines but no resizing horizontally. The windows desktop would be a mess though.


Also that screenshot was using bicubic resize and the digi cam wasn't focusing quite right. It's much sharper with Lanczos.
 

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Quote:
Originally Posted by Jesse S
Actually that makes me wonder what 720x720p would look like. No scanlines but no resizing horizontally. The windows desktop would be a mess though.


NO RESIZING.....just a lousy picture. :D
 
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