[Kwintv] some problems with kdetv 0.83 and saa7134

[Dirk Ziegelmeier]

On Monday 04 October 2004 22:57, Hans-Peter Jansen wrote:
> Sorry for the wrong identifier, but the XVIDEO plugin is more
> interesting for me, since it allows for scaled fullscreen (without
> switching resolutions)..
The v4l plugin can do that, too and is much more capable than the xvideo 
plugin (deinterlacing, overscan...). The configuration of you v4l plugin must 
be wrong. It should be as follows:

- "Use overlay" should be disabled
- Video output method: "XVideo" or "XVideo with SHM"
- Depending on you CPU speed, "full frame rate"

> > Maybe the driver reports the correct maxwidth? So kdetv should not
> > set it to a larger value...
>
> I've attached outputs of kdetv (switching to FS and back) and v4l-info
> (Sorry Gerd, I know, you got them already, sorry..)
>
> Dirk, could you point me to the method, where XVideo Scaling happens?
Nowhere ;-) It's done by the v4l bridge in the X-server. The only thing kdetv 
does is to tell the X-Server it should display video in a widget with the 
desired size (XPutVideo() in kvideoio/kxv.cpp). The v4l bridge then captures 
from the tv card into memory and uses the graphics card's hardware scaling to 
resize the image.

BTW, the v4l plugin also uses hardware scaling, since the XvPutImage call is 
usually accelerated by the graphics card (in fact, that's why it exists). 
XvPutImage (kvideoio/qvideostream::displayImage()) converts an YUV image to 
RGB, resizes it and displays it in a widget.

> BTW: I noticed a mysterious Xv port 70 "Matrox G-Series Backend
> Scaler", why cannot it be used?
That's no video port, but an image port. It's used by the v4l plugin to scale 
the image.

Dirk