Re: VidHD: New 1080p HDMI video card for the AppleII [message #371504 is a reply to message #371497] |
Wed, 01 August 2018 16:29 |
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Originally posted by: John Brooks
On Wednesday, August 1, 2018 at 11:21:48 AM UTC-7, STYNX wrote:
> On Wednesday, 1 August 2018 19:42:46 UTC+2, STYNX wrote:
>> i will try to find a frequency response chart for the Sony BVM.
>
> The only thing I found was, that my Sony BVM has a smaller than 3dB dampening at 10Mhz for RGB.
>
> I have thought about the frequency again and if the pixel-clock is 16mhz, the highest frequency would be 8mhz (1->0 full 'wave'). So filter response may not completely explain the blending of colors since the 8Mhz is completely in the specification (only 3dB dampening).
>
> The RGB drivers are coupled in the schematic through an inductor in series with a resistor. Maybe there is something here? Or the electron guns themselves are acting as an inductor or a coil? I'm no analog wizard and cannot contemplate what actually happens there...
>
> -Jonas
Nice photos!
I'm not sure the Sony BVM is a high-quality choice for 14MHz and 16MHz GS images, compared to the AppleColor RGB monitor.
Here is a picture of IIGS 80-column white text on a blue background from my AppleColor GS RGB monitor. If you zoom up a few times on the letter M, you can see there are 7x columns @ 14MHz in the M character font, and 8x rows.
The single blue pixels do have some filtering/ringing from the adjacent white pixels, but they are clearly darker than the white pixels.
https://drive.google.com/file/d/1gbtEdbl5tA5aO_JDTqoOk_5sv0d y4dCc/view
Similarly, the 640-res Finder has alternating columns of bright lines and dark lines, though the contrast is somewhat reduced for 16MHz alternating pixels.
-JB
@JBrooksBSI
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Re: VidHD: New 1080p HDMI video card for the AppleII [message #371511 is a reply to message #371504] |
Wed, 01 August 2018 19:44 |
Michael J. Mahon
Messages: 1767 Registered: October 2012
Karma: 0
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Senior Member |
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John Brooks <jbrooks@blueshiftinc.com> wrote:
> On Wednesday, August 1, 2018 at 11:21:48 AM UTC-7, STYNX wrote:
>> On Wednesday, 1 August 2018 19:42:46 UTC+2, STYNX wrote:
>>> i will try to find a frequency response chart for the Sony BVM.
>>
>> The only thing I found was, that my Sony BVM has a smaller than 3dB
>> dampening at 10Mhz for RGB.
>>
>> I have thought about the frequency again and if the pixel-clock is
>> 16mhz, the highest frequency would be 8mhz (1->0 full 'wave'). So filter
>> response may not completely explain the blending of colors since the
>> 8Mhz is completely in the specification (only 3dB dampening).
>>
>> The RGB drivers are coupled in the schematic through an inductor in
>> series with a resistor. Maybe there is something here? Or the electron
>> guns themselves are acting as an inductor or a coil? I'm no analog
>> wizard and cannot contemplate what actually happens there...
>>
>> -Jonas
>
> Nice photos!
>
> I'm not sure the Sony BVM is a high-quality choice for 14MHz and 16MHz GS
> images, compared to the AppleColor RGB monitor.
>
> Here is a picture of IIGS 80-column white text on a blue background from
> my AppleColor GS RGB monitor. If you zoom up a few times on the letter M,
> you can see there are 7x columns @ 14MHz in the M character font, and 8x rows.
>
> The single blue pixels do have some filtering/ringing from the adjacent
> white pixels, but they are clearly darker than the white pixels.
>
> https://drive.google.com/file/d/1gbtEdbl5tA5aO_JDTqoOk_5sv0d y4dCc/view
>
> Similarly, the 640-res Finder has alternating columns of bright lines and
> dark lines, though the contrast is somewhat reduced for 16MHz alternating pixels.
>
> -JB
> @JBrooksBSI
>
Consistent with 3db down at 8mHz...
--
-michael - NadaNet 3.1 and AppleCrate II: http://michaeljmahon.com
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Re: VidHD: New 1080p HDMI video card for the AppleII [message #371568 is a reply to message #371552] |
Thu, 02 August 2018 20:54 |
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Originally posted by: John Brooks
On Thursday, August 2, 2018 at 11:48:41 AM UTC-7, STYNX wrote:
> On Thursday, 2 August 2018 20:39:39 UTC+2, STYNX wrote:
>
>> Same as above SHR 640 mode:
>> https://www.flickr.com/photos/88521483@N03/29938711278/in/da teposted-public/
>
> BTW: is someone able to explain the lighter gray line in the unselected drive icon?
>
> It is the same b&w pattern as in the rest of the drive icon just shifted one pixel (of 640 mode) to the left...
> It seems to create a different gray tone....
>
> -Jonas
I suspect the lighter gray is caused by the phospher placement on your CRT aligning with the GS dither timing (particularly the green phosphor). On my AppleColor CRT and VidHD's output, the shifted dither does not have the light gray look of your display.
-JB
@JBrooksBSI
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Re: VidHD: New 1080p HDMI video card for the AppleII [message #371577 is a reply to message #371568] |
Fri, 03 August 2018 03:18 |
STYNX
Messages: 453 Registered: October 2012
Karma: 0
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Senior Member |
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On Friday, 3 August 2018 02:54:39 UTC+2, John Brooks wrote:
> On Thursday, August 2, 2018 at 11:48:41 AM UTC-7, STYNX wrote:
>> On Thursday, 2 August 2018 20:39:39 UTC+2, STYNX wrote:
>>
>>> Same as above SHR 640 mode:
>>> https://www.flickr.com/photos/88521483@N03/29938711278/in/da teposted-public/
>>
>> BTW: is someone able to explain the lighter gray line in the unselected drive icon?
>>
>> It is the same b&w pattern as in the rest of the drive icon just shifted one pixel (of 640 mode) to the left...
>> It seems to create a different gray tone....
>>
>> -Jonas
>
> I suspect the lighter gray is caused by the phospher placement on your CRT aligning with the GS dither timing (particularly the green phosphor). On my AppleColor CRT and VidHD's output, the shifted dither does not have the light gray look of your display.
>
> -JB
> @JBrooksBSI
On my BVM, Panasonic and AppleColor it is a bit lighter in color!
AppleColor RGB:
https://www.flickr.com/photos/88521483@N03/43818125381/in/da teposted-public/
full desktop:
https://www.flickr.com/photos/88521483@N03/42009469600/in/da teposted-public/
Your guess with placement makes no sense. How would that influence a RGBRGBRGBRGB pattern with a 2x finer pitch than the signal separation? The patterns are symmetric! if white gets 5 or whatever number of 'subpixels', so does black. But this is seemingly not the case as the width of the white pixels is varying depending on the position on the screen. Apple has implemented a method to use one 4-color palette on the even and another 4 color palette on the odd pixel columns in 640 mode (a bit like HGR)... maybe there is something to that? Maybe the even-odd pixels do not have the same width in the signal?
And how do you think it is possible for the BVM to display perfect 80col text with blended colors in SHR? Even at the shown extremely low contrast&brightness settings there is still blending effect and only a _hint_ of the alternating signal pattern. The signal is alternating, the visual representation on the display is not. It is blended and I have shown that in more than one picture.
Here is a low contrast/brighness image of the GSOS desktop on the AppleColor:
https://www.flickr.com/photos/88521483@N03/43101533994/in/da teposted-public/
It looks like true white is actually a black-white pattern... following your thoughts...
-Jonas
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