[MPlayer-users] speaking of vo... (was How I take a screenshot ??)

[ivanova]

On Sat, 21 Aug 2004 19:55:22 +0000
Roberto Togni <r_togni at tiscali.it> wrote:

> On 2004.08.21 20:36, ivanova wrote:
> > On Sat, 21 Aug 2004 21:09:31 +0300
> > Jan Knutar <jknutar at nic.fi> wrote:
> > 
> > > On Saturday 21 August 2004 19:51, The Wanderer wrote:
> > >
> > > > As a separate note, the one potential problem which I knew about
> > but
> > > > forgot to mention in the previous suggestion is that the
> > > > grab-screenshot-with-separate-program method will not work with
> > some -vo
> > > > methods, because pausing MPlayer and switching window focus
> > repeatedly
> > > > will soon result in the video window blanking to blue (or, at
> > least, it
> > > > does for me).
> > >
> > > Even if it didn't, all you'd see on the screenshot would be the  
> > blue
> > anyways,
> > > atleast with xvidix, xmga, xv, xover and most likely xvmc. Or some
> > other
> > > colour ;-)
> > 
> > While we are on the subject: What is the difference between the
> > different vo
> > modes? I got -vo x11 to work with scrot. What makes it different to
> > all the
> > other modes?
> some vo (like x11) draws the image on the screen, while other vo (like  
> xv) use an overlay.
> What's the difference?
> 
> With x11 the image is converted to the display colorspace (usually  
> rgb24) by MPlayer, and then it's drawn on the screen like any other  
> window. So the image is really in screen memory area, and a snapshot  
> program can grab it.
> 
> With xv MPlayer paint a solid colour rectangle on the screen (blue or  
> purple, i don't remember exactly but that's not so important), and tell  
> the video card to treat that color as a colorkey. Then MPlayer put the  
> video frames to a special memory area in the video card, and the video  
> card takes care of converting the image to the correct colorspace and  
> to replace the solid colored rectangle with the image.
> In this case, a screen grabber program gets the rectangle (that's  
> phisicalli painted in video memory) and not the image (that does not  
> exist, it's created on the fly while sending data to the monitor).
> 
> Advantages:
> - source image is usually YV12 (like mpeg video), that's 12bit/pixel  
> compared to 24bit/pixel fior RGB, so you need less memory bandwidth
> - colorspace conversion (computationally expensive) is performed in  
> hardware.

Thanks, that really clears things up. ;)
Where does xvidix and gl/gl2 fit into this? I also see a xover mode, I assume it
is just a generic version of xv. 
Also, what is the difference between DGA and framebuffer?