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

[Dirk Ziegelmeier]

On Tuesday 24 February 2004 16:13, Ziegelmeier Dirk wrote:
> > > Now about QtVision (as I started to use it): in v4l
> > > (/dev/video) mode I don't
> > > have overlay, so the application consumes about 3-6 % of my
> >
> > Please explain in more detail, what does it mean? Do you use the latest
> > snapshot / did you check out recently?
>
> Yes, I updated from CVS recently (but to be sure, I did a cvs up again).
>
> > Did you configure v4l plugin to use
> > overlay?
>
> I'd like to, but I can't. If I do so, I get nothing, but a black picture in
> the TV window. Oops, not the case anymore. It seems that I've missed your
> latest fixes, although I watch the kde-cvs list and update when something
> interesting is committed there. But a new problem appeared. If I use
> overlay
> in the video4linux plugin, I can't make the image to appear fullscreen. It
> remains are ~780x580. This is the maximum I get also if I rescale the
> QtVison
> window (I'm using a 1280x1024 desktop).
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.

> > Did you check the console debug output?
>
> In what part are you interested in?
It may have read "overlay disabled" somewhere ;-)

> > > CPU (Athlon
> > > XP2000+) and sometimes I even see "frame skipping" effects.
> > > But in XVideo
> > > mode the image quality is worser. Is this known and is there
> > > a fix planned
> > > for it? In the old kwintv there is no such problem.
> >
> > For XVideo display mode of v4l plugin, your graphics card has to support
> > scaling, if not, it's worse.
>
> May be the case. I have an older Geforce2MX400 card.
>
> > Does the XVIDEO plugin work?
>
> This is the one that uses the XVideo port 77, isn't it? It works, but the
> quality is not so good.
Yes this is the XVIDEO plugin. It also uses the card's scaling abilities, so 
the quality problem may be the same as above.

> > Did you play with the config options of the
> > v4l plugin?
>
> Yes, I've tried to. Here are some information about the CPU usage in every
> mode (top is using 1-1.5%, the rest is mainly used by the two qtvision
> processes and X):
>
> Video4Linux plugin, overlay enabled:
> 1. XVideo w/ shared memory: 3.5-12%, usually around 4-5%, 1.3-2.5% system
> (when it's high, X uses~7%, qtvison is usually between 3-5%)
> 2. XVideo: same situation
> 3. X11 w/ shared memory: same
> 4. X11: same
> I think all being the same was expected.
Yes, because the display variants are not used when overlay is on.

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.

> Video4Linux plugin, overlay disabled:
> 1. XVideo w/ shared memory: 18-20% user, 3.5-4% system (X: 6-7%, qtvision1:
> 7.5- 8.5%, qtvision2: 3.5-4.5%)
> 2. XVideo: 11-12% user, 13.5-14.5% system (X:12.3-13.3%, qtvision1:
> 4.9-6.9%,
> qtvision2:2.5-4.5%)
> 3. X11 w/ shared memory: 17.5-19.5% user, 2.5-3.9% system(X: 6.4-6.9%,
> qtvision1: 7.9%, qtvision2: 3.4-3.9%)
> 4. X11: 18-22% users, 13-15.5% system (X: 13.3-13.8%, qtvision1:
> 12.8-14.8%,
>
> qtvision2: 2.9-3.9%)
>
> As you see, the load is rather high.
Yes, due to grabbing, memcopying and scaling (might be done in software for 
XVideo by your graphics card driver).

> XVideo plugin: 3.5-13% user, 1.5-2.5% system (X: 0.5-8%, qtvision1: 2-2.5%,
> qtvision2: 1-1.5%)
OK, it only uses graphics card and grabber card resources. CPU does not have 
to do anything.

> I did the same test for kwintv 0.8.12: the kwintv and X process did not
> appeared on the top of the most CPU intensive processes, the 0.6-2.3% load
> was generated by other processes, like top. X was around 0.5-1%.
> So I'd say that there was almost no CPU usage caused by kwintv.
That's quite low, I don't know what kwintv did for video display to be so 
resource efficient. Maybe I look into the code once more.

> > PS: Did not reply to list, since I do not want the world to read/archive
> my
> > work email address.
>
> I also replied only to you now. ;-)
>
> Andras


Dirk