Re: [Ql-Users] Q40 and Q60 video controller for flatscreen monitors

[Peter Graf via Ql-Users]

Am 01.05.2018 um 20:55 schrieb Thierry Godefroy via Ql-Users:
> On Tue, 1 May 2018 19:26:56 +0200, Peter Graf via Ql-Users wrote:
> 
>> Most flatscreens misunderstand the signal as 800x600, leading to bad
>> interpolation.
> 
> Among the 3 LCD monitors I own, only the latest is able to (badly) sync
> the Q60 video signal and it does as if it would be a 640x480 VGA mode
> with 38.3KHz horizontal and 71.4Hz vertical frequencies, so the sampling
> of the pixels is extremely bad, and it fails to display the last 32
> lines...
> 
> Interestingly, my last functionning CRT monitor, that displays the Q60
> mode just fine (thanks to the 100% analogous processing of the signal),
> also reports a 640x480 38KHz/71Hz mode.

Sorry I wasn't precise. I was not referring to the original signal, but
the general issue with 1024x512, after improving timings for flatscreen
already. I generated more suitable 1024x512 signals (with relaxed
front/back porch timings) that are accepted but misunderstood.

Peter
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Re: [Ql-Users] Q40 and Q60 video controller for flatscreen monitors

[Thierry Godefroy via Ql-Users]

On Tue, 1 May 2018 19:26:56 +0200, Peter Graf via Ql-Users wrote:

> Most flatscreens misunderstand the signal as 800x600, leading to bad
> interpolation.

Among the 3 LCD monitors I own, only the latest is able to (badly) sync
the Q60 video signal and it does as if it would be a 640x480 VGA mode
with 38.3KHz horizontal and 71.4Hz vertical frequencies, so the sampling
of the pixels is extremely bad, and it fails to display the last 32
lines...

Interestingly, my last functionning CRT monitor, that displays the Q60
mode just fine (thanks to the 100% analogous processing of the signal),
also reports a 640x480 38KHz/71Hz mode.

Thierry.
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Re: [Ql-Users] Q40 and Q60 video controller for flatscreen monitors

[Dave Park via Ql-Users]

On Tue, May 1, 2018 at 12:26 PM, Peter Graf via Ql-Users <
ql-users@lists.q-v-d.com> wrote:

> Dave Park via Ql-Users wrote:
>
> > What are the frames per second and number of lines in the image?
>
> Originally 72 Hz, 512 visible lines.


​Even just counting the visible pixels, the upgrade position looks
untenable.​

​512x256x72  =​  9,437,184 dot clock
​800x600x50  =​ 28,800,000 "
​800x600x25  =​ 14,400,000 "
​1080x720x30 =​ 19,440,000 "
1080x720x15 =  9,720,000 "
1080x720x12 =  9,331,200 "

Hmmm, I see the limitation...

It strikes me that 1080P at half intended frame rate, then externally frame
doubling using new hardware on the output would give 1080P/24, /25 or /30,
but... It requires an external frame doubler. That could be as simple as a
pair of FIFOs and a small CPLD though.

I wonder if 12fps would cause people to complain about responsiveness
during online gaming ;)




-- 
Dave Park
d...@sinclairql.com
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Re: [Ql-Users] Q40 and Q60 video controller for flatscreen monitors

[Peter Graf via Ql-Users]

Dave Park via Ql-Users wrote:

> What are the frames per second and number of lines in the image?

Originally 72 Hz, 512 visible lines.

> What 'legal' signal is it most similar to?

At design time it was fine to use any legal resoltion of a multisync CRT
monitor. The idea was to stay at the QL-style 2:1 ratio on 4:3 screen,
epscially for the QL modes 4 and 8.

Most flatscreens misunderstand the signal as 800x600, leading to bad
interpolation.

> Is it possible to alter the frame rate

Yes I did that, as I wrote.

> and/or to supply a pixel clock signal?

Yes, but it is at the very maximum. Otherwise I would of course have
increased it already.

> This could open up the option of DVI conversion. (I have never
> owned a QX0 and don't know if it uses a card or custom logic.)

There is a slight chance to generate a pseudo FullHD signal, but only at
unusually low frame rate. I keep looking at that, but it is difficult,
logic was already optimized extremely to fit the chip. And not all
monitors would accept it.

> I'm just trying to understand the problem and why the LCD monitor won't
> sync the nonstandard signal.

Some do sync, but usually blur the picture by sampling 800 points on a
1024 horizontal line.

> If it's just one aspect of the signal it may
> be easily fixable and retain full screen display.

Not easily fixable, I would have done so.

Peter
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Re: [Ql-Users] Q40 and Q60 video controller for flatscreen monitors

[Dave Park via Ql-Users]

I have delved into video conversion and signal processing in some detail
for the QL, I have a few questions about the original signal:

What are the frames per second and number of lines in the image?
What 'legal' signal is it most similar to?
Is it possible to alter the frame rate, and/or to supply a pixel clock
signal? This could open up the option of DVI conversion. (I have never
owned a QX0 and don't know if it uses a card or custom logic.)


I'm just trying to understand the problem and why the LCD monitor won't
sync the nonstandard signal. If it's just one aspect of the signal it may
be easily fixable and retain full screen display. If there are multiple
elements to the problem, then not. Having access to the pixel clock and
being able to manipulate the frame rate to 30 FPS - or even better 60FPS -
 would be extremely useful.

On Tue, May 1, 2018 at 9:47 AM, Wolf via Ql-Users 
wrote:

> Hi all,
>
>
> > I have developed an alternative video controller for Q40 and Q60:
>
>
> I've been testing this for a few months now. At last I can use the Q60
> with a more modern flatscreen with VGA and 1024*768 resolution.
>
> The image is correctly displayed, but the bottom third of the monitor
> remains black (since the Q60 y resolution is 512 pixels, not 768).
>
> Kudos to Peter for making this work.
>
> Wolfgang
>
>
>
> On 01/05/2018 11:34, Peter Graf via Ql-Users wrote:
>
>> Hello,
>>
>> I have developed an alternative video controller for Q40 and Q60:
>>
>> http://qlforum.co.uk/viewtopic.php?f=2=2434
>>
>> All the best
>> Peter
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>>
>>
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>



-- 
Dave Park
d...@sinclairql.com
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Re: [Ql-Users] Q40 and Q60 video controller for flatscreen monitors

[Wolf via Ql-Users]

Hi all,


> I have developed an alternative video controller for Q40 and Q60:


I've been testing this for a few months now. At last I can use the Q60 
with a more modern flatscreen with VGA and 1024*768 resolution.


The image is correctly displayed, but the bottom third of the monitor 
remains black (since the Q60 y resolution is 512 pixels, not 768).


Kudos to Peter for making this work.

Wolfgang


On 01/05/2018 11:34, Peter Graf via Ql-Users wrote:

Hello,

I have developed an alternative video controller for Q40 and Q60:

http://qlforum.co.uk/viewtopic.php?f=2=2434

All the best
Peter
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