Increase screen resolution via composite output?

Hi,
Is there anyway to increase the resolution from 654x480 (I think) via
composite output? It seems to be stuck on that resolution only.
TIA
Reply to
chris
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The resolution of a TV is not better than that. At least, in composite video mode. It is best to check what input modes are offered by the monitor you want to use (e.g. VGA, DVI) and convert the HDMI output to that mode using one of the available conversion gizmos.
Reply to
Rob
Ah, so a hardware limitation?
Well that's a problem then as several of the python games available in Raspian don't fit the screen. So, at best you can't see the whole game and at worst you can't even play the game.
OK.
Reply to
chris
On Mon, 02 Dec 2013 13:04:13 +0000, chris declaimed the following:
A very ancient one... Given the 480 line limit: NTSC, not a PI limit, per se, but a limit on the display device.
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	Wulfraed                 Dennis Lee Bieber         AF6VN 
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Reply to
Dennis Lee Bieber
Well, more a limit on the bandwidth of the signal, since even inexpensive color CRTs are capable of somewhat more resolution.
It was the (economic) choice of tuned circuit filtering that cut the luminance bandwidth of analog NTSC receivers to about 3MHz, even though the standard easily supports 4+MHz.
Of course, that's still too little for crisp 80-column text, for which 8MHz is a good start and 12MHz is getting pretty nice.
The diagnostic is the relative brightness of single-pixel-width vertical strokes and single-line horizontal strokes. If the luminance bandwidth is satisfactory, they will be the same brightness. If it is insufficient, the vertical strokes will be dimmer.
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-michael - NadaNet 3.1 and AppleCrate II: http://home.comcast.net/~mjmahon
Reply to
Michael J. Mahon
The gory details are in en.wikipedia.org/wiki/NTSC#Color_encoding
The presence of the color subcarrier at 3.6MHz means that that part of the luminance (brightness) aignal has to be lost, even with a monochrome receiver handling a monochrome signal, as otherwise a signal with a subcarrier would produce unwanted interference with the picture. It was an unavoidable necessity when color was added to an existing monochrome standard and had to be done with backward compatability.
As a result to get good resolution on a TV it is necessary to use S-video or component video (RGB+sync) inputs. In practice the most common method is to use the SCART connector, which has component video inputs among other things.
On the pi the only way I can see which might achieve that is to use an HDMI-VGA converter to produce RGB+sync, then connect these signals to a SCART connector, and select a suitably low screen resolution so that the signals are within range of the TV.
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Alan Adams, from Northamptonshire 
alan@adamshome.org.uk 
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Reply to
Alan Adams
Summarised as 'If I wanted to get to a decent display, I wouldn't start with a TV'
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Ineptocracy 

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Reply to
The Natural Philosopher
It depends on what kind of TV. We have not heard what TV the poster used. When it is an old CRT TV or a low-end LCD, sure that is true.
But it might also be that the TV actually is an LCD screen with TV function and VGA input, but no HDMI. In that case, it can probably achieve much better picture quality via a HDMI->VGA converter and the VGA input than can ever be achieved via either CVBS or HDMI->RGB->SCART.
That is because the panel is often better than is required for TV, e.g. 1024x768 or 1280x768.
(a TV with a 1920x1080 panel probably has HDMI)
Reply to
Rob
OK. So, shouldn't the Pi/Raspbian be made to work well through any of the support output modes?
Currently the python games - which is what most kids are going to try first - don't all work well with the composite output. The games don't fit in the composite resolution and thus you can't reach all the buttons.
Reply to
chris
Don't the kids have an HD TV in their bedroom? I have...
Reply to
Rob
Weren't you just told it's not the RPi that's limiting the output quality?
Reply to
Rob Morley
When I studied this a long time ago, this concept, or dilema, was called "constant luminence"
IIRC, with a monochrome receiver with no subcarrier filtering, you actually got back some of the lost brightness, due to the inherent CRT grid-cathode rectification of the highly saturated parts of the signal.
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Graham. 

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Reply to
Graham.
No, the CRT grid never goes positive WRT the cathode.
The chroma subcarrier has an average (baseband) value of zero, so although it "dots" the display, adjacent "dot" luminances average to the original luminance. That's what allows unmodified B&W TVs to display the signal correctly in monochrome--hence, "compatible"--which was its big selling point.
It's worth pointing out that several early personal computers and video games had dot clocks that were multiples of the chroma subcarrier frequency so the dots were in exactly the same locations as the pixels. This had the added advantage that colors could be displayed using appropriate patterns of on/off pixels (e.g.: Apple II).
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-michael - NadaNet 3.1 and AppleCrate II: http://home.comcast.net/~mjmahon
Reply to
Michael J. Mahon
Perhaps it will help to think of the composite output as a means of viewing the text console, that happens to do graphics as a bonus.
Have you edited your config.txt file and played with the overscan settings etc?
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Graham. 

%Profound_observation%
Reply to
Graham.
When the Pi runs RISC OS, the physical output and the display mode as far as the OS are concerned are detached. The OS can think it's running at 1920x1080 and the monitor might only be 1366x768, and the GPU will downscale. It generally does it quite nicely, though it will never be as sharp as 1:1 modes.
There are framebuffer_width and framebuffer_height settings in config.txt - it may be worth playing with them to see if you can make a bigger 'virtual' mode where the games have enough space.
Theo
Reply to
Theo Markettos
On Tue, 03 Dec 2013 10:50:29 GMT, Alan Adams declaimed the following:
I don't think I've ever had a device with that particular connector... Lot's of RCA phono: composite, component (NOT RGB... Luminance, Blue - Luminance, Red - Luminance) With S-Video at some intervening point between composite and component inputs... VGA, DVI, HDMI
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	Wulfraed                 Dennis Lee Bieber         AF6VN 
    wlfraed@ix.netcom.com    HTTP://wlfraed.home.netcom.com/
Reply to
Dennis Lee Bieber
Err, OK. Not really the point, but thanks anyway.
Reply to
chris
Indeed, but the default software should at least be usable with any of the supported outputs. If the composite output is limited to 480 lines then all the apps should be able to work at that resolution.
Not all TVs have HDMI or DVI inputs.
Reply to
chris
I'm giving one as a present to a nephew, but am not sure what hardware they have to hand. I just want to cover the eventuality that they can only connect via composite.
No. I'll have a look. ta.
Reply to
chris
The SCART is a European 21 pin input/output connector,carrying amongst other signals audio, CVBS (composite), RGB, and sometimes Y/C
It has its critics, including me, but it can probably be argued that it has simplified interconnects for the average person.
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Graham. 

%Profound_observation%
Reply to
Graham.

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