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User:CarstenK/Screen aspect-ratio (view source)
Revision as of 08:08, 12 August 2008
, 08:08, 12 August 2008wrong aspect ratios. standard vs widescreen 16:9. PAL black borders. non-circles
===Wrong aspect ratio... 16:9 widescreen or normal.... PAL black borders?===
Maybe [[libogc]] and GX is just at a low level where it actually doesn't handle
non-square pixel aspect ratio, either that or there is a bug in it? This maybe
''might'' explain the black border issue some PAL users are reporting too.
I thought the lib provided a 640x480 surface so I was surprised when I could
never draw a perfect square or circle on my LCD. In standard mode everything
was always too tall and almost looked correct in 16:9 but not quite.
Some PAL users reported black borders on the edges of the HBC and independently
for other programs too. The circles containing arrows at the left and right of
the HBC don't look circular to me but that could be by design? In the HBC source
were those arrows ''really'' originally circles and not tall ovals?
For many Wiibrew this ultimately doesn't matter one iota. I do play
[[Homebrew_apps/MahJongg_Wii|MahJongg]] stretched full-screen to 16:9 to avoid
black borders and enjoy it fine yet this aspect ratio thing
[[Talk:Developer_Tips|deeply troubles me]].
'''Update:''' After experimenting with [[GRRLIB]] 3.01a and patching it, I found
how to draw perfect (correct) circles on an NTSC LCD TV
'''in both 16:9 widescreen and standard''' mode. This method can also be applied
to programs directly accessing GX without GRRLIB but needs to be calibrated for
PAL.
It probably has only to be tweaked a little for '''PAL''', please let me know
how my patch works for you in the EU. The
[[http://grrlib.santo.fr/forum/viewtopic.php?id=47 patch is in the GRRLIB forums],
you should also try the
[http://grrlib.santo.fr/forum/viewtopic.php?id=45 other great patches by Wil]
which were used during my experiments.
My numbers may be slightly off because I just used a 16ths inch ruler pressed
against the screen (albeit flat LCD) to measure the centre lines of the width
and height of circles, then fudged numbers in GRRLIB until the width the height
looked the same. Keep in mind if you have a CRT the values you need may be
slightly off due to calibration, but still would be interested to hear whether
PAL users can use the same numbers as I used and have things look right, but
I suspect not....
NTSC TVs use non-square pixels, I think 11/10 and PAL uses 1.094:1 yet I can't
figure those numbers into any calculation to arrive at the values I found
experimentally to get a correct aspect ratio with GX using GRRLIB.
If anyone can demonstrate a calculation to arrive at something close to my
numbers or the numbers [[Talk:Developer_Tips|Pepsiman used for PAL]] I would
be very interested.
I should note here I suspect emulators will not benefit from or should even be
considering any of this at this time, this discussion probably will only benefit
Homebrew apps, unless there turns out to be a bug or something in libogc that
should be patched. Most console emulators probably already output images at
non-square pixel ratios true to the originals because a TV was the original
expected output.
Microsoft provides some video test files at various pixel aspect ratios which
may come in handy (below).
I have a test program for drawing various circles and squares on the screen if
anyone is interested. If people even care about this and there is enough
interest this page can be moved.
The goal here is to provide:
* a consistant output no matter what display PAL/NTSC
* an easy, standard way of coding whether directly with GX or a library like GRRLIB
* an easy way to optionally implement widescreen 16:9 for homebrew while maintaining correct aspect ratio
It doesn't have to be perfect but to me currently aspect ratio seems "broken"
as-is and it would be nice to have simple examples and code to encourage
homebrew developers to implement optional widescreen capabilities.
Please add responses at the very bottom.
[[User:CarstenK|CarstenK]] 08:08, 12 August 2008 (CEST)
===External Links===
* [http://en.wikipedia.org/wiki/Pixel_aspect_ratio Wikipedia:Pixel_aspect_ratio]
* [http://www.bbc.co.uk/commissioning/tvbranding/picturesize.shtml BBC Guide to Picture Size (PAL)]
* [http://en.wikipedia.org/wiki/Ntsc#External_links Wikipedia:NTSC]
* [http://en.wikipedia.org/wiki/Pal Wikipedia:PAL]
* [http://www.microsoft.com/windows/windowsmedia/howto/articles/NonSquarePixel.aspx] Microsoft Nonsquare Pixel test video files
Maybe [[libogc]] and GX is just at a low level where it actually doesn't handle
non-square pixel aspect ratio, either that or there is a bug in it? This maybe
''might'' explain the black border issue some PAL users are reporting too.
I thought the lib provided a 640x480 surface so I was surprised when I could
never draw a perfect square or circle on my LCD. In standard mode everything
was always too tall and almost looked correct in 16:9 but not quite.
Some PAL users reported black borders on the edges of the HBC and independently
for other programs too. The circles containing arrows at the left and right of
the HBC don't look circular to me but that could be by design? In the HBC source
were those arrows ''really'' originally circles and not tall ovals?
For many Wiibrew this ultimately doesn't matter one iota. I do play
[[Homebrew_apps/MahJongg_Wii|MahJongg]] stretched full-screen to 16:9 to avoid
black borders and enjoy it fine yet this aspect ratio thing
[[Talk:Developer_Tips|deeply troubles me]].
'''Update:''' After experimenting with [[GRRLIB]] 3.01a and patching it, I found
how to draw perfect (correct) circles on an NTSC LCD TV
'''in both 16:9 widescreen and standard''' mode. This method can also be applied
to programs directly accessing GX without GRRLIB but needs to be calibrated for
PAL.
It probably has only to be tweaked a little for '''PAL''', please let me know
how my patch works for you in the EU. The
[[http://grrlib.santo.fr/forum/viewtopic.php?id=47 patch is in the GRRLIB forums],
you should also try the
[http://grrlib.santo.fr/forum/viewtopic.php?id=45 other great patches by Wil]
which were used during my experiments.
My numbers may be slightly off because I just used a 16ths inch ruler pressed
against the screen (albeit flat LCD) to measure the centre lines of the width
and height of circles, then fudged numbers in GRRLIB until the width the height
looked the same. Keep in mind if you have a CRT the values you need may be
slightly off due to calibration, but still would be interested to hear whether
PAL users can use the same numbers as I used and have things look right, but
I suspect not....
NTSC TVs use non-square pixels, I think 11/10 and PAL uses 1.094:1 yet I can't
figure those numbers into any calculation to arrive at the values I found
experimentally to get a correct aspect ratio with GX using GRRLIB.
If anyone can demonstrate a calculation to arrive at something close to my
numbers or the numbers [[Talk:Developer_Tips|Pepsiman used for PAL]] I would
be very interested.
I should note here I suspect emulators will not benefit from or should even be
considering any of this at this time, this discussion probably will only benefit
Homebrew apps, unless there turns out to be a bug or something in libogc that
should be patched. Most console emulators probably already output images at
non-square pixel ratios true to the originals because a TV was the original
expected output.
Microsoft provides some video test files at various pixel aspect ratios which
may come in handy (below).
I have a test program for drawing various circles and squares on the screen if
anyone is interested. If people even care about this and there is enough
interest this page can be moved.
The goal here is to provide:
* a consistant output no matter what display PAL/NTSC
* an easy, standard way of coding whether directly with GX or a library like GRRLIB
* an easy way to optionally implement widescreen 16:9 for homebrew while maintaining correct aspect ratio
It doesn't have to be perfect but to me currently aspect ratio seems "broken"
as-is and it would be nice to have simple examples and code to encourage
homebrew developers to implement optional widescreen capabilities.
Please add responses at the very bottom.
[[User:CarstenK|CarstenK]] 08:08, 12 August 2008 (CEST)
===External Links===
* [http://en.wikipedia.org/wiki/Pixel_aspect_ratio Wikipedia:Pixel_aspect_ratio]
* [http://www.bbc.co.uk/commissioning/tvbranding/picturesize.shtml BBC Guide to Picture Size (PAL)]
* [http://en.wikipedia.org/wiki/Ntsc#External_links Wikipedia:NTSC]
* [http://en.wikipedia.org/wiki/Pal Wikipedia:PAL]
* [http://www.microsoft.com/windows/windowsmedia/howto/articles/NonSquarePixel.aspx] Microsoft Nonsquare Pixel test video files