CurtPalme.com Home Theater Forum

[JorisS]

Hi all,

been contemplating going digital lately, then changed my mind after watching a couple of movies in anamorphic 2.35:1 with "black" bars above and below and decided to for starters get a new screen, 2.35:1 and somewhat wider to fill the wall space optimally

Screen is now built and mounted, obviously I'll have to move the NEC back a fair bit though as the previous screen was a 16:9, about same height but a lot less wide. Current ceiling mount of the NEC was optimized for that screen with respect to phosphor usage, so I cannot go much wider as it is.


I'm currently feeding a signal from a HTPC through HDMI into the NEC's Moome HDMI card (latest version).

Now I've been thinking about how to setup the image. If I use regular 1080i or 1080p from the HTPC and I configure the image to cover the screen, I guess I'm compressing the image in vertical sense? Besides, if I start a movie in 2.35:1 it will still show the bars I guess, but everything compressed. So I guess I need to get the HTPC to output a 2.35:1 signal? Is it, as usual, powerstrip for the win? Any suggestions for resolution and timings? The majority of the material we watch is in 2.35:1, I don't mind that for the odd 16:9 we will have black bars on the sides. Or should I instead somehow feed 1080i/p and have it overlap the black borders of the screen top and bottom in such a way that a 2.35:1 movie ends up exactly within the white area? This way I'd lose part of the image when watching 16:9 though.... what does the HTPC do if I use a 2.35 output resolution and run a 2.35:1 movie? Does it then exactly fit, as I would want it to? And with 16:9 it will adjust to resolution height and add the black bars on the sides?


Please help

No help --> ditch the CRT and go digital. You guys wouldn't want that, right?

Cheers
//Joris

[garyfritz]

DVDs support only two image formats: 4:3 and 16:9. Widescreen movies use the 16:9 format but include the black bars in the image.

I'm not an HTPC or scaler expert, but: The simplest solution is to continue using 16:9 in your projector and realize that you'll have black bars above/below the image. If you want to optimize the bandwidth usage of your video circuitry, you can use a scaler or HTPC to crop the black bars out of the video stream, thus sending a 2.35:1 image to your projector. Then you'd need a 2.35:1 memory in your projector for that.

You'll pull your projector back far enough to have the full width of the phosphor cover the width of your screen. If you watch 16:9, you'll probably want to have it fit inside your 2.35:1 screen -- which means black bars on the left/right. This means the 16:9 image will be a small image in the center of your phosphor.

[JorisS]

Hi Gary, thanks for the reply! Some follow up questions:

[garyfritz]

I suspect most 720p and 1080p mkv's are 16x9. I believe 1080p is defined to be 1920x1080, which is a 16x9 AR. They probably pulled them off DVDs or BR disks, which carry 1080p in 1920x1080 format -- so they would include the bars.

How to crop the black bars: you need an HTPC/scaler expert to answer that one. I think you just set it up to say "ignore the first x lines after the front porch, and the last y lines before the back porch," and only the center video content comes out the end. Then you have a 1920x817 video signal, which uses 3/4 as much bandwidth as a full 1920x1080 signal. You spend all of your video bandwidth on desired picture content instead of using some of it to display black lines. I don't know if that makes enough difference to make it worth the bother. Maybe so, if you're pushing the limits of your projector -- like if you're trying to get a PG9 to display 1080p.

So you either display 1920x1080 with black bars, or you display 1920x817 with no black bars. You set up your projector to do the right thing depending on which signal format you use. You shouldn't have to cut off any of the image.

[JorisS]

Hrm but seeing as I just mounted a 2.35:1 screen I would not be very interested in displaying 1920 x 1080 obviously. I don't even know how I'd setup the image as if I were to fill the width of the screen I'd be outside of it in vertical aspect :S

Not quite sure about the source material, many of the movies come in formats like 1920 x 800 I believe.


If I create a custom resolution with powerstrip, for example, at 1920 x 800. Then I setup the PJ for that, image covering the screen. Then I play a movie with 1920 x 800 resolution - will it then still show the black bars top and bottom and simply compress everything in vertical direction, because the movie is in fact 1920x1080 but with black bars encoded? Or does the PC add the black bars itself to fill up 1920 x 800 to the 1920x1080 resolution?


Dang need to figure this out

From what I understood digitals simply use zoom - setup 16:9 so it fills the screen vertically, then for 2.35:1 aspect ratio material zoom to fill it horizontally. In that case I guess the pj is actually lighting up the screen border above and below picture, but with proper screen and border material it won't be noticeable?

[dturco]

I'm not sure about the P.C. but a lumagen will only use the area of the "active picture" in the 1920x800. The black bars if they were present in the source material simply are not scanned or displayed since there is no active picture in the black bars.

It's hard to wrap your head around but after a while it makes sense Only Active area in which something will move is used.

That's why it's called Active Area Scanning.

I think a P.C is exactly the same, pretty sure.

[garyfritz]

[Nashou66]

Read this first:

http://archive2.avsforum.com/avs-vb/showthread.php?t=737385

Also you can set up the screen location and PJ using a 16x9 image/Disc. I used the AVS HD disc as it has a 2.35 aspect ratio
pattern, i wish they would add a 2.4. But the 2.35 works ok. 2.4 is a little more narrow hight wise as i miss a little of the 2,35 image in my set up. What you have to hope for is your PJ has enough adjustment range in the vertical size adjustment.
Because using 1920x800p@xHz the image will look to tall, it will go over the screen top and bottom. In the Marquee there was a resistor mod. I think the NEC has enough adjustment or you might be able to squeeze it down in the PC. I used a lumagen HDQ and it had an adjustment as well. Thats all you need. Now for 16x9 the image will be just as tall just more narrow. you can make cheap ad on mask for the sides if you want. One thing to think about is for movies with subtitles you need to have the ability to move the subtitles up into the image area, the Oppo player does this and I am sure some PC player programs can as well.

Athanasios

[Hdale85]

MKV files do not have the black bars hard coded in, that's just what the computer add's in to fill up the extra space. If you go into a program like Media Player Classic and look at the video properties it should tell you what resolution it's running.

[JorisS]

Thanks for the replies! Will start off with moving the pj so I can fill the width of the screen, then take things one step at a time with the info provided above

I do not own a Lumagen nor do I currently want to invest more in the CRT, so I want to try and work things out with the HTPC. I will have to run at a custom 1920x817 resolution, right? Otherwise 16:9 material will end up off screen?



I'm basically diving into this part because I am imagining myself it will improve the experience big time for the 2.35:1 material which most of the stuff we're watching seems to be, and because I like testing new things. Quite frankly with the improvements in the digital PJ area and the current prices I too realize it's mostly stubornness and hobbyism that's keeping me from abandoning the CRT (plus while it's working, it's basically running at no cost - not considering power consumption that is )

Anyway, I want to first give the CRT a go, if I manage to get things working and with a nice image that will do fine for now - if it fails or if I'm very unhappy with the result I'm going to take a drastic step and plunge into digitals again...

Cheers
//Joris

[dvh99]

i am not sure how you will be able to pull this of, 16:9 and 2.35:1 use the same amount pixels horizontal.
so projecting a 16:9 image on a 2.35:1 screen means you will have to make the raster smaller horizontal and adjust vertical size a bit because the timings will differ a bit via powerstrip.
you need 2 memories of course and save 2 profiles under powerstrip.

personally i would have chosen a 16:9 screen to fit the 2:35 inside and use 2 profiles under powerstrip to reduce bandwidth.
craig started a thread here some time ago about covering the screen with a black cloth top and bottom for 2.35:1 purpose.

[JorisS]

[JorisS]

On a sidenote (was about to make a new topic for this but probably better to toss it in here):


After mounting the 2.35:1 screen I tried quickly if I'd manage to fill it with the pj hanging where it does now (it doesn't).

While doing so I noticed that with all the picture settings set to default (ctrl + normal) the crosshair pattern is asymmetrical? I.e. the right bar on the crosshair is about 95cm whereas the left bar is only about 80cm. Why is this

It's rather confusing and annoying when doing a setup with the medium and fine raster, I do not understand why it is so either? Is it related to some other setting I have to reset to default as well?


Apologies if this is an utter noob question, fact remains this struck me as odd and I do not understand why it is so, and whether or not it is normal/ok/problematic...

Cheers
//Joris

[Nashou66]

That is where you need to use linearity controls to make each grid square the same size. Not familiar with the NEC's but in the marquee they are C linearity and S linearity. C is for center region and S is for the side regions. It might be the same on the NEC's. This works for Vertical and Horizontal .

Athanasios

[Boilermaker]

On your NEC you need to fist go into the "alignment" menu and choose the "linearity" and "linearity-balance" controls.
Turn off the red and blue guns as you should only be concerned with the green at this point. The right and left arrows will adjust the vertical linearity and the top and bottom arrows adjust the horizontal. The "linearity-balance" moves each side in opposite directions - you will easily see this.

When you get green done, go into the "convergence" menu and use the same menu items to do both red and blue to align on top of the green. Simple as that!

Probably be a good idea to "normalize" all point convergence before you do this.


Bob

[dvh99]

fact remains that you will have to decrease the raster size horizontally for 16:9 under a different memory.
linear distortion is normal and you could end up with a value of 15 or 16, on a marquee this is common.

[Hdale85]

If you set up a 2.35:1 resolution that is lower then your 16:9 resolution then when you watch 16:9 material you will be looking at less resolution. Maybe not a big deal? But something to think about.

[dvh99]

setting up a crt for 2.35:1 is a bad idea cause even more phosphor remains unused, like i said ditch the 2.35:1 screen and use curtain blanking if you want, there are still a lot of series in 16:9 and a lot of "older" movies too, i watched eyes wide shut again yesterday 16:9.

[Hdale85]

Well, if all you're ever going to do is 2.35:1 and never change to anything else it probably wouldn't matter much to the user.

[Nashou66]

If i had a single CRT again i would still use a 16x9 screen and go with CIW. build a masking system to mask of the top and bottom of the screen. Warm up the PJ with a full white 16x9 field for 15 minutes each time to avoid any 2.4 aspect ration burn in.

its the best way to go for a single CRT projector.

Athanasios