BluRazPi
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Composite Output Aspect Ratio Won't Change! Help!

Sun Mar 08, 2015 9:25 pm

Hi all. I just broke out my old (already?!) Model B to tinker with last night; I decided to run it with my 5" 16:9 widescreen display just for fun :D , but I ran into a speed bump. The last time I used that 5" display was with an older 2014 something raspbian image and I had the config.txt file all setup so that the composite display output would show the right aspect ratio (16:9 for this display) and the overscan was all set perfectly. I have since then wiped all my cards and have put the latest raspbian image onto them. Well so when I went to edit the config.txt file on the new raspbian image, I had to add the 'sdtv_aspect=3' line as usual because it isn't included by default, and I also tweaked the overscan settings a little. I rebooted, and the overscan had changed a little ( I'll have to spend some time fine tuning it), but the aspect ratio won't change :| ! I have tried changing to various 'sdtv_mode=x' settings and still no luck. I have double and triple checked that aspect line to make sure I spelled it right and even retyped it, but it just won't change to 16:9. Just to clarify, this is all taking place on the latest 2015-2-31 build (I think) of Raspbian on a later version Model B Raspberry Pi. Does anyone have any ideas as to why this aspect ratio setting won't change?

Any help would be greatly appreciated,
BluRazPi

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mahjongg
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Re: Composite Output Aspect Ratio Won't Change! Help!

Sun Mar 08, 2015 10:04 pm

are you really using composite video (through the RCA output connector)?
AFAIK, both PAL and NTSC have fixed aspect ratio's that cannot be changed.

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DougieLawson
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Re: Composite Output Aspect Ratio Won't Change! Help!

Sun Mar 08, 2015 10:16 pm

mahjongg wrote:are you really using composite video (through the RCA output connector)?
AFAIK, both PAL and NTSC have fixed aspect ratio's that cannot be changed.
According to http://www.raspberrypi.org/documentatio ... fig-txt.md

You can set it in /boot/config.txt with
sdtv_aspect=1 # 4:3
sdtv_aspect=2 # 14:9
sdtv_aspect=3 # 16:9

Or with
tvservice -c "MODE ASPECT" # for example tvservice -c "PAL 16:9"
or
tvservice --sdtvon="MODE ASPECT"
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mahjongg
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Re: Composite Output Aspect Ratio Won't Change! Help!

Sun Mar 08, 2015 11:57 pm

okay, i did not know that, resolution will stay the same though....

Thats why they sometimes call PAL "576i" because it has a fixed vertical resolution of 576 lines, and is interlaced.
http://en.wikipedia.org/wiki/576i

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DougieLawson
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Re: Composite Output Aspect Ratio Won't Change! Help!

Mon Mar 09, 2015 8:45 am

mahjongg wrote:okay, i did not know that, resolution will stay the same though....

Thats why they sometimes call PAL "576i" because it has a fixed vertical resolution of 576 lines, and is interlaced.
http://en.wikipedia.org/wiki/576i
4:3 will have a different horizontal resolution to 16:9 or 14:9
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Burngate
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Re: Composite Output Aspect Ratio Won't Change! Help!

Mon Mar 09, 2015 1:14 pm

DougieLawson wrote:4:3 will have a different horizontal resolution to 16:9 or 14:9
My memory may be playing up.

The standard PAL signal only allows signals up to about 5MHz, which gives 700-or-so active pixels across a line, and 575 or 576 active lines.
Whether the display spreads those pixels so they're in a rectangle with some simple relationship between its height and width is not determined by the PAL signal.

There is a signal on the SCART system that can tell the display what to do.

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Re: Composite Output Aspect Ratio Won't Change! Help!

Thu Mar 12, 2015 12:25 am

Burngate wrote: Whether the display spreads those pixels so they're in a rectangle with some simple relationship between its height and width is not determined by the PAL signal.
No indeed it is not, and I really doubt, the PI will give out more pixels per line if a widescreen ratio is set up, or am I wrong?
All I ever heard about it is that it would downscale a (which one is still a question to me) HDMI mode to create a PAL or NTSC video resolution.

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