Tweaking VGA->SCART RGB timings

720x480 and 720x576 are non-square pixel modes - and with most OSs will give you odd shaped pictures.

When I ran my RGB SCART -> VGA cable about 5 years ago (with XP MCE and an old Radeon card into my 16:9 Sony WEGA 28" CRT) I designed square-pixel 1024x576/50Hz modes and 854x480/60Hz 16:9 mdoes for 16:9. This meant the UI was 16:9 (fonts the right shape) and also the Media Center guide looked nicer (and you got more programme informaton on-screen!)

The timing was tricky to get right but it was pretty good for 16:9 stuff. (MCE will pillarbox 4:3 content into a 16:9 frame so I didn't bother with custom 768x576 and 640x480 4:3 modes)


I used Powerstrip.

The zoomed in issue is because CRTs overscan (and flat panels simulate it). Not a problem in MCE - but in normal Windows it's a pain (by making the task bar taller you can at least partially solve it). I used to use VNC to remotely log in from a laptop to do normal Windows stuff on the HTPC connected to the SCART TV. (Also useful for when Powerstrip didn't start...)

There is also a registry hack in MCE to avoid it trying to simulate overscan which caused nasty scaling/interlace tearing artefacts on 50i motion. (I was using the nVidia PureVideo MPEG2 decoder)

Ah - would only run with 576 lines if you are using it for UK video - that way you get 1:1 line matching. Anything else is likely to look pretty nasty.


1024x576/50Hz modes will work on a 4:3 TV - it will just appear horizontally squashed (so everything will look tall and thin)


Ah - that sounds very odd. I didn't ever try with nVidia as they didn't do Composite (i.e. mixed H and V) syncs when I looked at using them - only Radeons would do them (and I didn't want to build a sync combining cable.)


I'm afraid they've gone the way of all things - they may be lurking somewhere on google as quite a few people in the UK used them. Think the forum I posted them mainly in is now defunct.

These might be useful : PowerStrip timing parameters:
1024x576=1024,109,48,147,576,5,5,39,20846,41

Generic timing details for 1024x576:
HFP=109 HSW=48 HBP=147 kHz=16 VFP=5 VSW=5 VBP=39 Hz=25

VESA detailed timing details:
PClk=20846.00 H.Active=1024 H.Blank=304 H.Offset=93 HSW=48 V.Active=576 V.Blank=49 V.Offset=5 VSW=5

Linux modeline parameters:
"1024x576" 20.846 1024 1133 1181 1328 576 581 586 625 interlace +hsync +vsync

from here :

http://www.avforums.com/forums/compu...rt-rgb-11.html


AND - Here's a post I wrote from years gone by that worked for me:

PowerStrip timing parameters:
1024x576=1024,32,96,112,576,5,5,39,19750,312

Generic timing details for 1024x576:
HFP=32 HSW=96 HBP=112 kHz=16 VFP=5 VSW=5 VBP=39 Hz=25

Linux modeline parameters:
"1024x576" 19.750 1024 1056 1152 1264 576 581 586 625 interlace +hsync
+vsync

You'll want a 60Hz mode for US content - it will look horrible at 50Hz - so you might as well line-match that as well - rather than doing a scale.

Find a 854x480/60Hz interlaced mode for that.

If it has a SCART socket and was sold after about 1990 it is very likely it will support 60Hz via RGB SCART. Certainly every Sony set I've owned since 1993 has. I'd be more surprised if it didn't support 60Hz than if it did - though some early 100Hz CRTs didn't like 60Hz.

I can't watch 50Hz content at 60Hz - particularly native interlaced stuff - as the 10Hz judder caused by repeating every 5th frame screams at me. Watching any tickers on the news channels and you go from nice smooth fluid motion to juddery nastiness.

However I accept I'm a bit more susceptible to sub-par video quality as in my day job I watch broadcast quality stuff and part of my job is to spot those kind of artefacts and reject them!

4 resolutions :

768 x 576 / 50i for a 4:3 50Hz display
640 x 480 / 60i for a 4:3 60Hz display
1024 x 576 / 50i for a 16:9 50Hz display
854 x 480 / 60i for a 16:9 60Hz display

Horizontal line rate should be 15.625kHz for 50Hz displays and 15.73425Hz for 60hz displays (if you run at 59.94Hz which is what NTSC material actually runs at) or 15.750kHz for 60Hz (which isn't common for source material)

Total line count should be 625 for 50Hz, 525 for 60Hz.
Refresh rate should be 25 or 50Hz for 50Hz, 29.97 or 59.94Hz for 60Hz ideally.

Total line time should be 64us, and active line time should be 52us for 50Hz. Don't have the exact figures for 60Hz to hand but something like 63.55us and 52.66us respectively for total and active.

Can you alter the pixel clock rate? The active line times are out a bit - which means your image will be squashed horizontally in the two modes you've created?

In an ideal world, horizontally, you need to be able to have something like :

1260 total pixels each line for 1024 active pixels for 1024x576 at 50Hz.

This means 1260 x 625 x 25 pixels per second = 19.6875MHz is the pixel clock you need. If you can't achieve that then something close?

So assuming the following HORIZONTAL timings :

Total line = 64us = 1260 pixels
Active line = 52us = 1024 pixels
Horizontal blanking = 12us = 236 pixels
Line sync width = 4.7us = 93 pixels
Front porch = 1.65us = 32 pixels
Back porch = what's left = 5.65us = 111 pixels

Following the same maths for 768x576/50Hz :

For 768 active pixels each line, you have a total of 945 pixels each line?
945 x 625 x 25 pixels per second = 14.765625 MHz pixel clock?

Total line = 64us = 945 pixels
Active line = 52us = 768 pixels
Horizontal blanking = 12us = 177 pixels
Line sync width = 4.7us = 69 pixels
Front porch = 1.65us = 24 pixels
Back porch = 5.65us = 84 pixels

I haven't tried this for years - but ISTR I went back to standard 625/50Hz video timings, and calculated the various pixel widths of the signal elements from this. I also recall that I never quite got my head round the vertical figures - but it worked!

"Resolution within resolution" settings are for use when you have overscan and want to see the whole desktop. The video card outputs a 1024x576 video signal still - so the TV locks onto it - but the desktop only occupies a say 910 x 520 resolution desktop within this - with the driver putting black around the edges. Not a good idea for video - as you want to keep that line-mapped. But for desktop stuff it could be useful as a second video mode.

If that's the case - then I'd do whatever you can by tweaking the total line pixels and non active line pixels to get 15.625kHz and 25Hz as they are the two key figures to hit - a few pixels of stretch or squeeze horizontally isn't the end of the world, nor is tweaking the pixel clock.

However if the PC that the settings are eventually to run on is only ever going to feed a 16:9 display - then there is no need to have a 768x576 resolution - as 4:3 content will be pillarboxed in a 1024x576 desktop res anyway by most windows apps.

Another option is running at a non-square pixel res (ie 720x576 or 702x576) and putting up with slightly odd shaped Windows desktop, and configuring the player app to display full-screen (ignoring what it thinks is the 'right' aspect ratio for the desktop res) - but if you have to deal with a mix of aspect ratio sources (not just full-screen for your display) this isn't a great idea.

Windows thinks that pixels are square. Therefore a 720x576 resolution will, to Windows, be 11.25 : 9 (slightly narrower than 4:3 which is 12:9) Left to its own devices Windows will therefore crop/zoom/letterbox/black bar 4:3 and 16:9 sources to fit into a 720x576 11.25:9 desktop. If this output is actually stretched across a 4:3 screen or 16:9 screen it will be wrong or very wrong (as the 720x576 pixels in an SD video signal are NOT square)

By forcing the player app to ignore Windows resolutions/aspect ratio and stretch a 16:9 or4:3 image across the full 720x576 resolution - it would work ok.

720x480 and 640x480 should both be fine for 60Hz 4:3. 720x576 and 768x576 should both be fine for 50Hz SD 4:3. 640x480 not great for 50Hz content as you are scaling vertically (which can be nasty with interlaced content)

This is only the case if you can force Media Portal to ignore Windows aspect ratio. The UI won't look too bad.

However I'd avoid using them to feed a 16:9 display as the degree of UI stretch is likely to be horrible - distorting coverart, thumbnails, text etc.

Nope...

SD digital video is usually 720x576/50Hz or 720x480/60Hz (+/- a few pixels horizontally - 702x576 or 711x480 are the analogue equivalent resolutions)

This is true for both 4:3 AND 16:9 SD video... These are the broadcast production standards, and DVDs usually use them. SD TV broadcasts can use them (704x480, 704x576 are also common, as are 544x576 for both 4:3 and 16:9) The pixels aren't square at either aspect ratio - the resolutions are the same for both aspect ratios.

Confusing? Yep.

However when running an OS that only really likes thinking in square pixel resolutions (like Windows), if you want to keep circles circular with few problems, the following resolutions apply :

768x576 4:3 SD 50Hz
640x480 4:3 SD 60Hz
1024x576 16:9 SD 50Hz
844x480 16:9 SD 60Hz

If you want Windows content to be the right shape as well as video - then best running in one of the 4 resolutions above.


Yes - assuming you're happy coping with manual aspect ratio switching on your TV between 4:3 and 16:9 SD sources (and this can be an issue with a 4:3 display). You avoid a horizontal re-scale, but may have more issues keeping everything the right shape.

Nope - you're misunderstanding me.

720x576 is used full-screen for BOTH 4:3 and 16:9 standard def video - this IS really confusing if you think pixels are square - but they don't have to be.

The pixels in SD digital video aren't square in either case - the pixels are different shapes for 720x576 4:3 and 16:9 content. This is fine for DVD players, broadcast TV kit etc. as they are fully aware that the pixels are different aspect ratios when 720x576 is used for 4:3 or 16:9 and can adjust their processing accordingly (so circles are circular in both formats)

Where it falls down is computers. Most PCs and Macs can only cope with square pixels.

This means that you can't have a 4:3 or 16:9 resolution at 720x576 - you have to scale one of the dimensions to make the pixels square. For lots of reasons it is almost always better to scale horizontally rather than vertically.

Therefore a 16:9 resolution is 1024x576 and a 4:3 resolution is 768x576.

4:3 SD 720x576 DVD and broadcast content is thus scaled to 768x576 for 4:3 display and pillarboxed to be the central 768x576 section of a 1024x576 display for 16:9 displays. (Or you can chose other ways to display)

16:9 720x576 DVD and broadcast content is thus scaled to 1024x576 for 16:9 displays and letterboxed to a 768x432 section within a 768x576 display for 4:3 displays. (Or you can chose other ways to display)


The problem with running a 720x576 resolution to feed a 16:9 display is that the software handling the playback needs to know that the 720x576 is actually non-square 16:9 not square pixels 11.5:9. For 16:9 content most players are fine - you just tell them to stretch to full screen and ignore the aspect ratio conversion they may try to employ. However for 4:3 content this needs the player software to understand that the source is 4:3, the display is 16:9 and the resolution is 720x576 with pixels of a suitable aspect ratio for 16:9 display and to scale 4:3 720x576 accordingly. Some player software does this.

The reality is you are MUCH better off in Windows running 1024x576 square pixel resolutions for a 16:9 display. Everything just works - and you are unlikely to see horrific horizontal scaling artefacts on a CRT anyway.


Yep - just stick with 1024x576! (And 854x480 for 60Hz or 24Hz content if you need to)

Hi guys!

I also use VGA-SCART connection. Would you show some pics about yours?

Regards,
joecontra

Hi!

I made my first VGA-SCART cable. The picture is just awesome. I wrote an article about it.
I link that after I'll be able to put URL's in my posts.

Regards,
joecontra

It should be working with your widescreen LCD TV. Then you would be able to set new widescreen resolutions in PowerStrip.

Regards,
joecontra

I also built my own VGA-SCART cable. I made a website about it:
story of my cable with pictures

Use VGA-SCART with WinModelines:
VGA-SCART and WinModelines

Switch between resolutions with one single keypress:
Hotkey Resolution Changer review

Regards,
joecontra