Old monitors Help

[pandy71]

Originally Posted by idrougge

First of all, the Amiga resolution is not 320x256 or any multiple thereof. There is overscan (or underscan) and a computer screen will take that into account. The resolution is more like 720x576, if we say that there even are horizontal pixels in an analogue video signal.
Furthermore, the electronics of an LCD won't even try to map those pixels uniformly to its native pixels. Why? Don't ask me.

True for resolution more explanation in this thread: http://eab.abime.net/showpost.php?p=566007&postcount=15 - Amiga resolution is directly correlated with pixel clock used by Amiga and because Amiga clock is different than ITU-R BT.601/BT.656 then typical LCD (PDP, OLED etc) will not match pixel. Amiga video signal will be re-sampled and this can't be avoided without reprogramming display acquisition chip.

Pixel clock for SDTV (601/656) is 1/13.5MHz where on Amiga it may be or 1/28.375160MHz (SHRES ECS/AGA) or 1/14.187580MHz (for HIRES) - it is quite clear that any standard display with 601/656 timing will degrade Amiga video signal in unavoidable way. Acquisition part in display can be reprogrammed but usually there is no datasheet available for chip thus there is no way to reprogram it.

Except SDTV 601/656 clock used by PAL and NTSC all above for Amiga are PAL values, NTSC use slightly faster pixel clock.

[demolition]

Originally Posted by idrougge

First of all, the Amiga resolution is not 320x256 or any multiple thereof. There is overscan (or underscan) and a computer screen will take that into account. The resolution is more like 720x576, if we say that there even are horizontal pixels in an analogue video signal.
Furthermore, the electronics of an LCD won't even try to map those pixels uniformly to its native pixels. Why? Don't ask me.

Yes, there are various levels of overscan but the monitor can 'window' this signal and sample it correctly. This is similar to how an Indivision would do it, although the Indivision has lots more options for fine tuning this window and the sampling frequency.
Regarding the horizontal resolution, this is why you have the pixel clock and phase adjustments available on the monitor. If they are set optimally, some monitors can achieve pixel-perfect sampling of the source signal in both X and Y. I know my Dell 2001FP can do it 100% accurately and if I disable any scaling and use 1:1 pixel mapping mode, it will map one Amiga pixel to exactly one LCD cell. It is easy to tell if it does it correctly if you set a background image which consists of alternating black and white pixels.

[Amiga1992]

To be honest, if there is no choice for you but to use a modern display, whatever its kind that is a flat panel, I would resort to a good scan converter like the Framemeister or the OSSC.

I think that's the only way to assure an image as close to the original as possible. But it 's not a cheap option.
For me the cheapest acceptable option is a free RGB CRT TV that supports RGB on SCART. I don't want to have a flat panel LCD/TFT or even a tube VGA CRT.

[pandy71]

Originally Posted by demolition

Yes, there are various levels of overscan but the monitor can 'window' this signal and sample it correctly. This is similar to how an Indivision would do it, although the Indivision has lots more options for fine tuning this window and the sampling frequency.
Regarding the horizontal resolution, this is why you have the pixel clock and phase adjustments available on the monitor. If they are set optimally, some monitors can achieve pixel-perfect sampling of the source signal in both X and Y. I know my Dell 2001FP can do it 100% accurately and if I disable any scaling and use 1:1 pixel mapping mode, it will map one Amiga pixel to exactly one LCD cell. It is easy to tell if it does it correctly if you set a background image which consists of alternating black and white pixels.

Nope - different pixel clock make impossible to correctly display Amiga video -Amiga pixel clock is way more higher than SDTV.
Some displays may have better software and perhaps they are able to deal with Amiga video but most of displays just resample Amiga signal with different sampling rate.
And b&w pattern may or not be OK if oversampling is used by display (commonly 27 or 54MHz sampling)

[grelbfarlk]

You have a couple options with newer monitors.
1) Get a monitor that syncs down to 15khz, the Dell U2410 is a good choice, it displays native 15khz modes just fine. Advantage is that this might be the simplest option but you may have to hunt for an LCD that supports 15khz signals. Also some of these monitors might display games just fine but may not like interlaced modes or doublescan modes or other odd amiga modes that you didn't know you might want to use.

2) Get a flicker fixer like the Indivision or the then use any LCD monitor that has a VGA or DVI port which matches the version of Indivision you bought. Disadvantage is that the Indivision is rather expensive but at least it's internal so you cut down on cord clutter.

3) Get one of the external generic flicker fixers or scan converts. These vary from terrible to good. The cheap ones like the GBS-8220 are bad and cause tearing, input lag and other effects which you will probably notice. The good ones like the OSSC will cause less input lag and less other ugly effects and have a nice feature of scanline emulation. Scanline emulation will insert black lines between each line of color or data which will more closely match what you're used to seeing on an old CRT. Cost can be $20-$200+ depending on what you end up buying. Scanline emulation does make old games and low res stuff like classic amiga games look better by letting your brain fill in the blanks and give the illusion of higher detail which does not exist. Which is often the complaint when someone gets a flickerfixer

When buying an LCD like buying an old Multiscan CRT look for one that has the most variety of supported resolutions and for an LCD, one that is 1080p or 1920x1080 native, though 1920x1200 is even better.

Here is an incomplete list of monitors supporting 15khz modes most of which should work for Amigas.
http://15khz.wikidot.com/

You will find dozens of threads if you search for 15khz Amiga LCD monitors.

[idrougge]

Originally Posted by demolition

Yes, there are various levels of overscan but the monitor can 'window' this signal and sample it correctly.

I'm not saying it can't be done, all I'm saying that no such monitor has been made to this date, unless there is some top secret Sony broadcast reference LCD that handles this.

Originally Posted by demolition

Regarding the horizontal resolution, this is why you have the pixel clock and phase adjustments available on the monitor. If they are set optimally, some monitors can achieve pixel-perfect sampling of the source signal in both X and Y. I know my Dell 2001FP can do it 100% accurately and if I disable any scaling and use 1:1 pixel mapping mode, it will map one Amiga pixel to exactly one LCD cell. It is easy to tell if it does it correctly if you set a background image which consists of alternating black and white pixels.

I know my 2001fps (I've owned four of them) will always exhibit banding, and to add insult to injury, they won't remember their settings.

[demolition]

Originally Posted by idrougge

I know my 2001fps (I've owned four of them) will always exhibit banding, and to add insult to injury, they won't remember their settings.

What do you mean by 'banding' exactly? My 2001FP samples the Amiga signal 100% pixel-accurate so apparently it is able to lock to the exact pixel clock. I have no interference patterns which would show if there were any misalignments in the sampling frequency or phase.

Not being able to remember the settings is annoying yes, but I have sort of gotten used to it by now.

[idrougge]

The picture is striped in dark and light stripes.

[demolition]

Originally Posted by idrougge

The picture is striped in dark and light stripes.

Well, that only happens is the pixel clock is not set correctly in the monitor.