Help with correcting VGA to component picture on a Toshiba HD CRT - AVS Forum
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post #1 of 13 Old 01-05-2013, 03:40 PM - Thread Starter
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Hey everyone. I'm new to this forum but I've used the threads as a source of info in the past. I could use some pointers on how to correct the image on my set. Thanks in advance for any useful tips!

I have a game system (Dreamcast) hooked up to the TV (Toshiba theatrewide, a direct view HD CRT). The DC's signal first goes through a VGA box, which carries its 480p signal. My goal in this whole set up is to maintain that 480p signal as perfectly as possible. The VGA box leads to a VGA to component (YPbPr) converter, which finally leads to the set. I'm using high-quality component cables, not those thin RCA ones. The converter is from Monoprice.

Now for the issue: the converter allows me to switch resolutions: 480p, 720p (which doesn't work on this TV), and 1080i. 1080i's picture suffers from bent geometry which I can't fix even through the TV's service menu - specifically, the lower part of the screen is squished vertically and the upper part is stretched. Besides that, I notice the interlace flickering, and prefer the original 480p signal. But 480p has another problem: the red signal seems to be overactive, making black areas look dark red or purplish. I can treat this by changing the Tv's tint/color, but the problem remains pretty noticeable.

Why would there be a color problem in converting a 480p VGA signal to 480p component? How might I solve it, or as a second option, the geometry issues for the 1080i signal?
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post #2 of 13 Old 01-05-2013, 09:56 PM
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That doesn't sound very solvable either through your TV or transcoder box. Monoprice doesn't always sell high quality stuff. I would send it back to them.

What I use is the Audio Authority 9a60: http://www.audioauthority.com/product_details/9A60

It gives stellar picture from my dreamcast, though it is shifted slightly left and down I think. Many games let you correct that though, and it's not that bad to begin with.

You can find it for about 20 bucks on ebay, so I would just return the monoprice thing.
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post #3 of 13 Old 01-06-2013, 02:54 PM - Thread Starter
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Originally Posted by CRTFTW View Post

That doesn't sound very solvable either through your TV or transcoder box. Monoprice doesn't always sell high quality stuff. I would send it back to them.
What I use is the Audio Authority 9a60: http://www.audioauthority.com/product_details/9A60
It gives stellar picture from my dreamcast, though it is shifted slightly left and down I think. Many games let you correct that though, and it's not that bad to begin with.
You can find it for about 20 bucks on ebay, so I would just return the monoprice thing.

The monoprice one also shifts the picture to the side. I managed to get more accurate colors by changing the 'RCUT' value in the tv's service menu, but I'll still consider getting the one you recommended if I can find it at a good price (ones on ebay right now are 65$+). One other problem with the monoprice converter is that it stretches the 4:3 source to the 16:9 screen, with no switch to choose aspect ratio. Does the audio authority box have the same problem?
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post #4 of 13 Old 01-06-2013, 07:57 PM
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I hope you recorded the original RCUT value because everything else not going through that monoprice adapter will look really off.

The audio authority transcoder doesn't stretch the image at all.

As far as the price goes, you just have to keep checking back. If you look at completed listings, you'll see that many have gone for under $20, one even went for $12.

http://www.ebay.com/sch/i.html?_sop=15&_sacat=0&_from=R46&_nkw=audio%20authority%20vga%20component&rt=nc&_pppn=r1&LH_Complete=1

Now is the time to pick these dudes up, though. TV manufacturers have started to nix their VGA connections, so anyone wanting to connect their Dreamcasts will have to convert to component or HDMI.
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post #5 of 13 Old 01-07-2013, 02:04 AM - Thread Starter
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I did take note of the original value. It didn't seem to make a difference to other 480p inputs, however.

I will keep an eye out for the AA box, but I'll also research why both of the converters would shift the image to the left and downwards. That's an odd coincidence. I'd prefer to not need to change the TV's horizontal and vertical position values whenever I switch consoles..
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Now is the time to pick these dudes up, though. TV manufacturers have started to nix their VGA connections, so anyone wanting to connect their Dreamcasts will have to convert to component or HDMI.
Component is next in line. Soon it'll just be HDMI and USB.frown.gif
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post #6 of 13 Old 01-07-2013, 08:58 AM
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I'm thinking you will never find a catch-all, one-stop solution to this problem. Here's why.

Every console since the dawn of time has worked with overscan, for various reasons. Dreamcast included. Ultimately though, overscan will be used more with older hardware to provide a full screen area, because the framebuffer of many games tends to be on the small side. TV to TV, overscan can vary, but you will find that if you can get the H+V alignment where you want it to get the most coverage with one broadcast on the same TV, every other broadcast tends to keep within that range.

The VGA Box is the wild card. It provides a high quality, non-interlaced (i.e. progressive) image. However, VGA is not a broadcast standard in the way that NTSC, PAL etc. are. It has no means to deal with overscan. So the only option is to turn it off. When using the VGA Box with your Dreamcast, the image that is given has no overscan at all, and it is frequently not providing the exact ratio that was originally intended--that only worked when stretching happened to account for overscan. This was not a problem in 1998 when the Dreamcast was designed. It was only ever presumed that you would have good access to the kind of H+V adjustments on your VGA monitor to correct the aspect and center as required. With your VGA Box now eliminating overscan, your transcoder altering the signal type for your HDTV, and your HDTV coming back to it looking for overscan, things have all manner of propensity to be wacked. At any rate, bad geometry is just bad geometry, you can be sure your box is not generating it. I'd expect geometry from other sources to be bad at 1080i if your Dreamcast through the VGA Box and transcoder box are showing bad geometry. Work with some test patterns, or other sources+modes with/without the transcoder box to confirm this, and go from there.
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post #7 of 13 Old 01-07-2013, 11:21 AM
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Yeah, what liquid snake said. I forgot that the image is shifted on my computer monitor too. So that's not an issue with transcoders, just the dreamcast and/or vga box.

The geometry itself isn't that bad though, the image is still mostly 4:3 as far as I can remember, maybe stretched vertically slightly. But the colors and sharpness are still great, so I still really like the outcome.
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post #8 of 13 Old 01-07-2013, 12:11 PM - Thread Starter
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I understand the overscan issues, in that the VGA signal takes up a full 480x640 area, while SD tv takes up much less than that. But this is different. I have no problem displaying the whole image, and my TV saves different settings for each resolution, so that my settings for 480p game systems don't cause the cable tv signal to shrink.
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I'd expect geometry from other sources to be bad at 1080i if your Dreamcast through the VGA Box and transcoder box are showing bad geometry.
You're right, all 1080i sources have this problem. I couldn't find what service menu item adjusts this property (vertical upper/lower stretch), so I gave up and switched my cable back to 480i. Solving that issue would be nice, but getting 480p to display without any issues is still priority.
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I forgot that the image is shifted on my computer monitor too. So that's not an issue with transcoders, just the dreamcast and/or vga box.
Really? I never noticed any shift when it was connected to my monitor. I'll check it again soon. I'm using the retro-bit VGA box with transparent plastic. If yours is the same, that might be the source of the shift.
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post #9 of 13 Old 01-07-2013, 12:53 PM
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Yeah, that's the same one I have. Just compare a 480p image coming from your computer to video from your dreamcast.

The problem with adjusting your TV for 480p from dreamcast is that 480p from other sources (Wii, PS2) will be thrown off. So I decided to just accept the slightly off-center dreamcast image, and just adjust it in-game where possible.
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post #10 of 13 Old 01-08-2013, 06:46 AM
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I can save you some time by advising you not to try using different VGA boxes. The "VGA Box" is really only a VGA Box in order to provide convenient access to all outputs the Dreamcast is capable of. The VGA box does nothing to create a VGA signal, it is merely a switch that activates the signal type you want. You can get the same VGA signal from the Dreamcast just by connecting the right wires. Any VGA connection you make is functionally identical to any other here.

So any difference that you are trying to effect here will have to come from either your display or in your case, your transcoder.
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post #11 of 13 Old 01-08-2013, 07:52 PM - Thread Starter
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Originally Posted by CRTFTW View Post

Yeah, that's the same one I have. Just compare a 480p image coming from your computer to video from your dreamcast.
The problem with adjusting your TV for 480p from dreamcast is that 480p from other sources (Wii, PS2) will be thrown off. So I decided to just accept the slightly off-center dreamcast image, and just adjust it in-game where possible.

I compared it to a PC>converter signal. That picture takes up the whole screen, in contrast to the dreamcast image, which has black borders on all sides (except only for the bootup white dreamcast logo and sega screens, which also take up the whole screen).
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Originally Posted by LiquidSnake View Post

I can save you some time by advising you not to try using different VGA boxes. The "VGA Box" is really only a VGA Box in order to provide convenient access to all outputs the Dreamcast is capable of. The VGA box does nothing to create a VGA signal, it is merely a switch that activates the signal type you want. You can get the same VGA signal from the Dreamcast just by connecting the right wires. Any VGA connection you make is functionally identical to any other here.
So any difference that you are trying to effect here will have to come from either your display or in your case, your transcoder.

I thought the problem must be the VGA box because FTW and I use the same one and see the same offset, but the signal it sends to my CRT monitor does not suffer from the same issue. This is weird.. it seems ONLY sending Dreamcast through a VGA box and a converter box, in 480p, messes with its color and/or placement.

I'm including a photo, which shows DC > VGA > Converter in 480p > RGB input on TV, displayed in 4:3 'normal' video mode. Notice the left black bar is thinner than the right; altering width expands and contracts everything on screen, including the grey pillar boxes, so cannot be used to correct it.

If there aren't any more ideas, i'll just live with it. Or I'll try to tackle the 1080i geometry issue instead.. The 1080i picture isn't as good as 480p, due to some interlace flickering, but it is still 20 times better than S-video. Thanks for your comments and info, guys!
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post #12 of 13 Old 01-09-2013, 10:14 AM
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Originally Posted by crackalackin View Post

I thought the problem must be the VGA box because FTW and I use the same one and see the same offset, but the signal it sends to my CRT monitor does not suffer from the same issue.

So, it's as I said. It is either happening at the display, or with the display + your transcoder. Since it is impossible for you to remove the transcoder, these two possibilities are not functionally distinct, and the only way you can isolate it as the cause (or not) is to try another transcoder, which can be a good way to go broke. Trying another Dreamcast VGA Box will be of no use here. If colour is correct enough, I would leave it alone and just use the display's controls to center and H+V when using the Dreamcast. But since colour is one of your big problems, well... another transcoder box may be your only resort.
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post #13 of 13 Old 01-09-2013, 11:49 AM
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Yeah, the offset is something the dreamcast itself does, as liquid snake said a few posts back. I forgot that the VGA Box doesn't really do anything, it just breaks out all the connections of Dreamcast AV port into standard connections. Some people solder a VGA connection directly from the board because they don't want to buy a VGA box.

So I bet if you send your dreamcast to your PC monitor, you will see the offset too, compared to a PC 480p signal (unless your monitor is an LCD, which may do some autocorrecting, I still use CRT's there too).

So yeah, I really think that your color issue will be solved by the Audio Authority converter. I certainly had no color issues with it on my Sony Hi-Scan TV.
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