[MPlayer-dev-eng] [patch][rfc] screenshot. Aspect Ratio problems

[ObsessiveMathsFreak]

> I don't see any reason why it should. Taking screenshots is not a
> normal function of watching a movie..
> 
> 
> There is no way to give a "what you see is what you get" output. It
> simply does not exist, since the scaled video only exists on the
> phosphors of your crt (cells of your crappy tft) for a split second. 

There's an abundance of third party screenshot capture programs. People 
really like taking screenshots. A lot of distros now include some kind 
of screen capture function as well, which is more or less a poor mans 
WYSIWYG. Xine does this, but also gets in wrong in the same way as the 
patch.


> They're not incorrectly sized but correct. They should just have
> different horizontal and vertical dpi in the png header to indicate
> the nonsquare samples (however I imagine vo_png is broken and does not
> set these headers correctly).
> 
I believe png can specify a pixel aspect ratio, for non square pixels, 
if that's what you mean. However, png viewers aren't required to account 
for this, and, though I haven't checked it, I doubt most do. vo_png 
might actually be taking this into account, but do the viewers?

It would be nice to somehow rescale (terminology?) the image to some 
required output before writing the png file. At the moment, I have 
absolutly no idea how to go about this outside of putting some 
additional filter or something in front of the screenshot filter. But 
would that screw up the output? Is it possible in some way to grab the 
pixels that were written to the screen, or have they been lost to the 
program forever?

Just so as you know. The source DVD I'm working from had the raw data as 
720x576 and then that was prescaled to 768x576. Hence all my trouble. I 
checked it and both the screenshot patch and vo_png both output their 
images as 720x576 when reading from the DVD, so I suppose this isn't 
just an issue with matroska. It's all, so complicated.

I think I'll just re-encode my movies using a scale filter instead of 
specifying an aspect ratio with matroska. I imagine this is a pretty 
esoteric issue anyway. But if matroska and the like get more popular, 
maybe people will want to specify aspect ratios there instead? If indeed 
there is anyone else out there crazy enough to give a danm!