[Kwintv] Re: The old KWinTV hangs with DMA enabled

[Andras Mantia]

Dirk Ziegelmeier wrote:
> Yes, that's right. This will only work if the grabber card supports
> scaling, bt8X8 chips only scale down, but not up. That's why many programs
> change the display resolution when they use overlay. QtVision does not
> implement this.

I understand.

> Yes this is the XVIDEO plugin. It also uses the card's scaling abilities,
> so the quality problem may be the same as above.
Ok.


> Basically the v4l plugin has two modes:
> 
> 1) Overlay: TV card grabs immediately into graphics card frame buffer.
> 
> 2) "Grab": TV gard grabs into a buffer which is painted by four different
> methods into a widget. XVideo supports scaling (maybe with the help of the
> graphics card), X11 is "dumb" copying without scaling. Shared Memory may
> speed up display by saving memcopies.
Yes, I knew this. 

> Yes, due to grabbing, memcopying and scaling (might be done in software
> for XVideo by your graphics card driver).

Understandable, but even in this case I found 20-25% CPU usage on a Athlon
XP 2000+ being rather high. I've just tested tvtime (that I don't really
like), and it's between 17-25%, but when it uses 25%, the targeted frame
rate is 50fps and I use a more CPU intensive deinterlacing method. I don't
blame you (or any qtvison author), and if you want good quality, you don't
care about CPU usage, but it's not nice to see frame skips and you may want
a mode when you can run the TV and compile the same time. ;-)

Taking into account the above, I think they show some reasons why the old
kwintv is still more usable for some people. But in the recent months also
QtVision made a big step forward, so I'm confident and hope that soon I can
drop the old kwintv and use (the more modern) QtVision.

Andras