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Successes and Challenges With Dreamcast VGA Cables and LCDs

by racketboy Wed Aug 02, 2006 9:16 pm

I just split up a part of the VGA Pictures thread to create a special thread specifically for discussing the special tweaks and such to get around potential issues with certain LCDs cooperating with the Dreamcast's resolution.



evildragon wrote:
racketboy wrote:
evildragon wrote:
Ramatut4001 wrote:If he's talking about the radio in his picture, he very likely does not have any RCA inputs. However, for the price of a decent FM transmitter, you could just buy some cheap PC speakers.

yea, it doesn't have any RCA jacks on it... being this radio must stay here for personal reasons, i can easily go for a cheap FM transmitter (as I can also use those things for many other things)


Ok, I guess I wasn't thinking clearly :)
Forgot about the radio thing (must have been distracted)
So yeah, a FM transmitter should do the trick

heh, i get distracted quite easily, lol

i figure it may be quite weird hearing Quake III Arena coming out of an old vintage radio, but it sure would be awesome! :P

Btw, I originally was using the VGA box on my LCD monitor this morning when it first arrived, but how come I had black bars on the left and right side of the screen? The LCD reported it had centered and sized the image properly, but it wasn't.. On my CRT, I have no problem getting the picture to fit...


Is the LCD a widescreen monitor? That may explain the bars...
Last edited by racketboy on Fri Aug 04, 2006 8:31 pm, edited 1 time in total.
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by evildragon Wed Aug 02, 2006 9:38 pm

racketboy wrote:
evildragon wrote:
racketboy wrote:
evildragon wrote:
Ramatut4001 wrote:If he's talking about the radio in his picture, he very likely does not have any RCA inputs. However, for the price of a decent FM transmitter, you could just buy some cheap PC speakers.

yea, it doesn't have any RCA jacks on it... being this radio must stay here for personal reasons, i can easily go for a cheap FM transmitter (as I can also use those things for many other things)


Ok, I guess I wasn't thinking clearly :)
Forgot about the radio thing (must have been distracted)
So yeah, a FM transmitter should do the trick

heh, i get distracted quite easily, lol

i figure it may be quite weird hearing Quake III Arena coming out of an old vintage radio, but it sure would be awesome! :P

Btw, I originally was using the VGA box on my LCD monitor this morning when it first arrived, but how come I had black bars on the left and right side of the screen? The LCD reported it had centered and sized the image properly, but it wasn't.. On my CRT, I have no problem getting the picture to fit...


Is the LCD a widescreen monitor? That may explain the bars...

no, it's a 4:3 shaped LCD... What's odd, is that when booting up the dreamcast, or when the SEGA license screen is there, it fills in every pixel of the LCD, but as soon as a game loads or i get to the DC's BIOS screen, the bars appear...

I also noticed something just now, the LCD says the resolution is 720x480, not 640x480.. I tested the LCD, I put my computer in 640x480, and the LCD sure enough said 640x480...

Seems weird...
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by Mozgus Thu Aug 03, 2006 4:21 pm

evildragon wrote:no, it's a 4:3 shaped LCD... What's odd, is that when booting up the dreamcast, or when the SEGA license screen is there, it fills in every pixel of the LCD, but as soon as a game loads or i get to the DC's BIOS screen, the bars appear...

I also noticed something just now, the LCD says the resolution is 720x480, not 640x480.. I tested the LCD, I put my computer in 640x480, and the LCD sure enough said 640x480...

Seems weird...

Same issues here. The black bars are because lotsa games don't actually run in 640x480. They tend to run in a frame thats about 90% of that size, because nearly all regular TVs chop off those edges. When the console doesn't have to render that 10% of the screen, it slightly helps performance.

My LCD sometimes said 720x480 as well. Not sure why. Not every game made it do that.
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by evildragon Thu Aug 03, 2006 5:07 pm

Mozgus wrote:
evildragon wrote:no, it's a 4:3 shaped LCD... What's odd, is that when booting up the dreamcast, or when the SEGA license screen is there, it fills in every pixel of the LCD, but as soon as a game loads or i get to the DC's BIOS screen, the bars appear...

I also noticed something just now, the LCD says the resolution is 720x480, not 640x480.. I tested the LCD, I put my computer in 640x480, and the LCD sure enough said 640x480...

Seems weird...

Same issues here. The black bars are because lotsa games don't actually run in 640x480. They tend to run in a frame thats about 90% of that size, because nearly all regular TVs chop off those edges. When the console doesn't have to render that 10% of the screen, it slightly helps performance.

My LCD sometimes said 720x480 as well. Not sure why. Not every game made it do that.

When I am booting Linux on my Dreamcast, the blue RedHat loader, is shifted to the left of the screen (and LCD says 720x480), and when I load X, with a resolution of 640x480, the LCD will still say 720x480..

I contacted my LCD manufacturer, and they actually have had calls about the Dreamcast on the LCD.. They told me that the dreamcast does indeed output a 720x480 signal, as it still is generating the same pixels as when on a TV (just not interlaced and low scan-rate), and that the games are indeed 640x480, but since the Dreamcast is technically in 720x480, there is a gap.. They told me that to correct this and compensate, they told me when in a video game, shift the picture to the left, and make the "sync clock" up to 100.. When I did that, sure enough, the picture fit perfectly on the LCD..

If this is the case, then this would explain why my old IBM VGA monitor would not sync up to the Dreamcast at all (the picture hanged off the screen and the CRT made a bad whistling sound)...
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by Mozgus Fri Aug 04, 2006 2:00 am

evildragon wrote:When I am booting Linux on my Dreamcast, the blue RedHat loader, is shifted to the left of the screen (and LCD says 720x480), and when I load X, with a resolution of 640x480, the LCD will still say 720x480..

I contacted my LCD manufacturer, and they actually have had calls about the Dreamcast on the LCD.. They told me that the dreamcast does indeed output a 720x480 signal, as it still is generating the same pixels as when on a TV (just not interlaced and low scan-rate), and that the games are indeed 640x480, but since the Dreamcast is technically in 720x480, there is a gap.. They told me that to correct this and compensate, they told me when in a video game, shift the picture to the left, and make the "sync clock" up to 100.. When I did that, sure enough, the picture fit perfectly on the LCD..

If this is the case, then this would explain why my old IBM VGA monitor would not sync up to the Dreamcast at all (the picture hanged off the screen and the CRT made a bad whistling sound)...

My very first post on this forum mentioned my similar issues here. Check this link and do a little dance for me. You're lucky your monitor has a setting for correcting the problem :(

http://www.dcemulation.com/phpBB/viewtopic.php?p=865051
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by racketboy Fri Aug 04, 2006 6:30 am

evildragon wrote:
Mozgus wrote:
evildragon wrote:no, it's a 4:3 shaped LCD... What's odd, is that when booting up the dreamcast, or when the SEGA license screen is there, it fills in every pixel of the LCD, but as soon as a game loads or i get to the DC's BIOS screen, the bars appear...

I also noticed something just now, the LCD says the resolution is 720x480, not 640x480.. I tested the LCD, I put my computer in 640x480, and the LCD sure enough said 640x480...

Seems weird...

Same issues here. The black bars are because lotsa games don't actually run in 640x480. They tend to run in a frame thats about 90% of that size, because nearly all regular TVs chop off those edges. When the console doesn't have to render that 10% of the screen, it slightly helps performance.

My LCD sometimes said 720x480 as well. Not sure why. Not every game made it do that.

When I am booting Linux on my Dreamcast, the blue RedHat loader, is shifted to the left of the screen (and LCD says 720x480), and when I load X, with a resolution of 640x480, the LCD will still say 720x480..

I contacted my LCD manufacturer, and they actually have had calls about the Dreamcast on the LCD.. They told me that the dreamcast does indeed output a 720x480 signal, as it still is generating the same pixels as when on a TV (just not interlaced and low scan-rate), and that the games are indeed 640x480, but since the Dreamcast is technically in 720x480, there is a gap.. They told me that to correct this and compensate, they told me when in a video game, shift the picture to the left, and make the "sync clock" up to 100.. When I did that, sure enough, the picture fit perfectly on the LCD..

If this is the case, then this would explain why my old IBM VGA monitor would not sync up to the Dreamcast at all (the picture hanged off the screen and the CRT made a bad whistling sound)...


Wow -- that's awesome that the manufacturer was that knowledgable and helpful in the matter!
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by evildragon Fri Aug 04, 2006 7:29 am

racketboy wrote:Wow -- that's awesome that the manufacturer was that knowledgable and helpful in the matter!

yea, surprisingly considering it's a cheap LCD manufacturer...

here's some pics.. one before the LCD is "pushed", and one after the LCD had it's sync clock "pushed".. they also told me that while the dreamcast is technically only rendering 640x480 on a 720x480 signal, I am essentially "lying" to the LCD where the image is...

http://img.photobucket.com/albums/v395/ ... before.jpg

http://img.photobucket.com/albums/v395/ ... dafter.jpg

sorry, had the cameras ISO setting too low..

What I do find interesting, is that since when the dreamcast boots up, it does fill EVERY pixel, even on the licensing screen, so that must mean the Dreamcast CAN render a 720x480 image... maybe it can go even higher with the VGA box... 8)
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by Mozgus Fri Aug 04, 2006 3:19 pm

evildragon wrote:yea, surprisingly considering it's a cheap LCD manufacturer...

here's some pics.. one before the LCD is "pushed", and one after the LCD had it's sync clock "pushed".. they also told me that while the dreamcast is technically only rendering 640x480 on a 720x480 signal, I am essentially "lying" to the LCD where the image is...

http://img.photobucket.com/albums/v395/ ... before.jpg

http://img.photobucket.com/albums/v395/ ... dafter.jpg

sorry, had the cameras ISO setting too low..

What I do find interesting, is that since when the dreamcast boots up, it does fill EVERY pixel, even on the licensing screen, so that must mean the Dreamcast CAN render a 720x480 image... maybe it can go even higher with the VGA box... 8)

::sigh:: I envy you. I love Samsung's 3 year warrantee and all, but they never even responded to me when I asked them about this issue. You're lucky your monitor lets you scale it right. Mine never lets me scale it far enough to the left. I don't have a "sync clock" option, but that is the method I was looking into. I know theres a way to modify a VGA cable so that it's sync is shifted slightly, but I don't know where to begin. Until then, I am stuck using my 20 inch NTSC TV.
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by evildragon Fri Aug 04, 2006 7:47 pm

Mozgus wrote:
evildragon wrote:yea, surprisingly considering it's a cheap LCD manufacturer...

here's some pics.. one before the LCD is "pushed", and one after the LCD had it's sync clock "pushed".. they also told me that while the dreamcast is technically only rendering 640x480 on a 720x480 signal, I am essentially "lying" to the LCD where the image is...

http://img.photobucket.com/albums/v395/ ... before.jpg

http://img.photobucket.com/albums/v395/ ... dafter.jpg

sorry, had the cameras ISO setting too low..

What I do find interesting, is that since when the dreamcast boots up, it does fill EVERY pixel, even on the licensing screen, so that must mean the Dreamcast CAN render a 720x480 image... maybe it can go even higher with the VGA box... 8)

::sigh:: I envy you. I love Samsung's 3 year warrantee and all, but they never even responded to me when I asked them about this issue. You're lucky your monitor lets you scale it right. Mine never lets me scale it far enough to the left. I don't have a "sync clock" option, but that is the method I was looking into. I know theres a way to modify a VGA cable so that it's sync is shifted slightly, but I don't know where to begin. Until then, I am stuck using my 20 inch NTSC TV.

here's a video of it being set... notice when I do start pushing the clock up, the picture shifts a "TINY" bit to the right with it, all I have to do is keep pushing the clock to 100, then the right part of the image will be cut off, but there will be a TINY gap on the left.. I just recenter the image by shifting the picture to the left slightly, and the WHOLE picture is perfectly fit then, with nothing being cut off...

also notice the LCD does now see the signal as 640x480.. It says ever since I lied to the LCD about the image.. essentially, this LCD "learns"...

http://blackevilweredragon.spymac.com/sync.AVI

(it's not divx, it's MotionJPEG, straight from the camera, so any media player can play it, it's just 6 megs)
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by Mozgus Fri Aug 04, 2006 8:13 pm

evildragon wrote:here's a video of it being set... notice when I do start pushing the clock up, the picture shifts a "TINY" bit to the right with it, all I have to do is keep pushing the clock to 100, then the right part of the image will be cut off, but there will be a TINY gap on the left.. I just recenter the image by shifting the picture to the left slightly, and the WHOLE picture is perfectly fit then, with nothing being cut off...

also notice the LCD does now see the signal as 640x480.. It says ever since I lied to the LCD about the image.. essentially, this LCD "learns"...

http://blackevilweredragon.spymac.com/sync.AVI

(it's not divx, it's MotionJPEG, straight from the camera, so any media player can play it, it's just 6 megs)

Yeah, I understand that. Doesn't apply to me though. My H-Position does not shift far enough to the left. I always have a big 1.5 inch black bar. Your "Clock" setting is the same as my "Coarse" setting. It slowly stretches the image so that on low resolution analog signals, you can try to find the size which distributes the pixels best amung the LCD's native display.
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