darry wrote on Today, 03:29:

As an optional functionality, configurable line multiplication, if possible, would be very nice. […]
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As an optional functionality, configurable line multiplication, if possible, would be very nice.

Would it be possible to line double 720x350 --> 1440x700 ( doubling the pixel clock into >25MHz range) and preserving 50Hz output?

Actually, that might be useful for all other supported modes such as 640x480 --> 1280x960 .

If I understand correctly, 320x200 modes are line doubled to 640x400 and then either letterboxed to 640x480 for output or stretched vertically vertically to a full 640x480 picture size, depending on the /V:x setting's value [1] . Alternatively, optionally line quadrupling them to 1280x800, if feasible, would be convenient too.

The main advantage of doing this, other than staying above 25MHz for the pixel clock, would to minimize the amount of scaling done by the monitor and maintain sharpness that might otherwise be lost due to the monitor's scaling algorithm.

I know it's likely an even taller order, but being able to manually tweak timings per mode (i.e. modelines) would really nice too.

Regardless, even if any of this is impossible, impractical, would require too much effort to be feasible or would possibly be of interest to almost nobody (except me), I will be happy to enjoy it as it is.

[1]
Vertical. LINES shows the lines as they are, centred. FILL stretches every mode
over the whole screen height, the way the original monitors filled their 4:3 tubes — a
320x200 game gets its 4:3 shape back

I guess you can output any arbitrary modelines given full control of the HDMI output, but whether they are useful or not depends on whether consumer displays and equipment can actually use them. I suspect the number of screens that would accept a 1440x700@50hz signal is almost zero.

NeoG_ wrote on Today, 03:48:

darry wrote on Today, 03:29:

As an optional functionality, configurable line multiplication, if possible, would be very nice. […]
Show full quote

As an optional functionality, configurable line multiplication, if possible, would be very nice.

Would it be possible to line double 720x350 --> 1440x700 ( doubling the pixel clock into >25MHz range) and preserving 50Hz output?

Actually, that might be useful for all other supported modes such as 640x480 --> 1280x960 .

If I understand correctly, 320x200 modes are line doubled to 640x400 and then either letterboxed to 640x480 for output or stretched vertically vertically to a full 640x480 picture size, depending on the /V:x setting's value [1] . Alternatively, optionally line quadrupling them to 1280x800, if feasible, would be convenient too.

The main advantage of doing this, other than staying above 25MHz for the pixel clock, would to minimize the amount of scaling done by the monitor and maintain sharpness that might otherwise be lost due to the monitor's scaling algorithm.

I know it's likely an even taller order, but being able to manually tweak timings per mode (i.e. modelines) would really nice too.

Regardless, even if any of this is impossible, impractical, would require too much effort to be feasible or would possibly be of interest to almost nobody (except me), I will be happy to enjoy it as it is.

[1]
Vertical. LINES shows the lines as they are, centred. FILL stretches every mode
over the whole screen height, the way the original monitors filled their 4:3 tubes — a
320x200 game gets its 4:3 shape back

I guess you can output any arbitrary modelines given full control of the HDMI output, but whether they are useful or not depends on whether consumer displays and equipment can actually use them. I suspect the number of screens that would accept a 1440x700@50hz signal is almost zero.

As a user of an OSSC and multiple monitors, I can say that monitors, especially newer ones, are often much more flexible on the timings they accept on HDMI/DVI input than their specifications or EDID would suggest.

Case in point, my rather pedestrian 2.5K MSI PRO MP275Q (EDID excerpt [1]) at 1440x700@50hz, in forced 4x3 mode :

[1]

1Monitor
2  Model name............... MSI MP275Q
3  Windows description...... MSI PRO MP275Q
4  Manufacturer............. MSI
5  Plug and Play ID......... MSI40C3
6  Serial number............ [OBFUSCATED]
7  Manufacture date......... 2024, ISO week 1
8  Filter driver............ None
9  -------------------------
10  EDID revision............ 1.3
11  Input signal type........ Digital
12  Color bit depth.......... Undefined
13  Display type............. RGB color
14  Screen size.............. 600 x 330 mm (27.0 in)
15  Power management......... Active off/sleep
16  Extension blocs.......... 1 (Unknown type)
17  -------------------------
18  DDC/CI................... n/a
19
20Color characteristics
21  Default color space...... Non-sRGB
22  Display gamma............ 2.20
23  Red chromaticity......... Rx 0.648 - Ry 0.330
24  Green chromaticity....... Gx 0.319 - Gy 0.617
25  Blue chromaticity........ Bx 0.150 - By 0.071
26  White point (default).... Wx 0.313 - Wy 0.329
27  Additional descriptors... None
28
29Timing characteristics
30  Horizontal scan range.... 30-155kHz
31  Vertical scan range...... 48-100Hz
32  Video bandwidth.......... 430MHz
33  CVT standard............. Not supported
34  GTF standard............. Not supported
35  Additional descriptors... None
36  Preferred timing......... Yes
37  Native/preferred timing.. 2560x1440p at 60Hz (16:9)
38    Modeline............... "2560x1440" 241.500 2560 2608 2640 2720 1440 1443 1448 1481 +hsync +vsync
39
40Standard timings supported
41     640 x  480p at  60Hz - IBM VGA
42     640 x  480p at  67Hz - Apple Mac II
43     640 x  480p at  72Hz - VESA
44     640 x  480p at  75Hz - VESA
45     800 x  600p at  56Hz - VESA
46     800 x  600p at  60Hz - VESA
47     800 x  600p at  72Hz - VESA
48     800 x  600p at  75Hz - VESA
49    1024 x  768p at  60Hz - VESA
50    1024 x  768p at  70Hz - VESA
51    1024 x  768p at  75Hz - VESA
52    1280 x 1024p at  75Hz - VESA
53    1280 x 1024p at  60Hz - VESA STD
54    1440 x  900p at  60Hz - VESA STD
55    1680 x 1050p at  60Hz - VESA STD

EDIT: While I haven't tried this specific resolution on my Philips 252B9, I have tried a number of oddball ones with various timings successfully.
EDIT2: Sorry for the crappy cellphone photos
EDIT3: No visible frameskipping according to my eyes and vsynctester.com either.

darry wrote on Today, 05:20:

EDIT3: No visible frameskipping according to my eyes and vsynctester.com either.

You're not going to get frameskipping when the monitor is being fed less frames than its native rate.

The first few serdavision cards are sent out, so no longer cards available for immediate shipping.
The next batch will be ready in approx 2 weeks, if interested go to https://serdashop.com/products/serdavision-hdmi

jmarsh wrote on Today, 07:27:

darry wrote on Today, 05:20:

EDIT3: No visible frameskipping according to my eyes and vsynctester.com either.

You're not going to get frameskipping when the monitor is being fed less frames than its native rate.

Frameskipping was not the appropriate word to use in this scenario. I was looking for any potential motion related artefacts and saw none.

Regardless, I would not expect to see any issues, especially not on a monitor that supports VRR and arguably does not have a "native" rate, but there was no harm in checking, as I hardly ever run this monitor at 50Hz.

dreamblaster wrote on Yesterday, 20:42:

KVM Nerd wrote on Yesterday, 15:20:

Will it also be able to output the native resolutions, for example 720x350 and/or 720x348 at roughly 50 Hz for Hercules cards, or just the mentioned resolutions? TIA!

720x350 at about 50 Hz isn’t possible over HDMI: its pixel clock (about 16 MHz) is below the 25 MHz minimum for HDMI/DVI, and most screens wouldn’t accept it anyway. Programs never notice the 60 Hz, because they see the card’s own retrace.

From what I know it should absolutely be possible using pixel repetition, which does exactly what it says. If enabled, pixels will be sent multiple times (for example x2 or x4) and the corresponding info field will tell the sink that it is enabled, so it can discard the redundant pixels accordingly. This way, the pixel clock would simply be doubled and be well over 25 MHz. This is a native HDMI feature.

Pixel repetition is the way HDMI spec calls for handling all the low resolutions that would fall below the minimum pixel clock limit. Only problem may be the GPIO on the RP2350 not being able to move fast enough on the doubled speed (HDMI/DVI freq on the output signals is 10x the pixel clock)