[Kwintv] Nearly fine, but still some standard problems at startup

[Christian Casteyde]

> I greatly appreciate your help in tracking this down. I _never_ experienced
> any of the problems on my box (as I already emailed in a private message to
> Chrisitan, I can flawlessly use qtvision to scan and display SECAM
> channels).

Well, as I post in an earlier message, I managed to scan after modifying
the channel detection time-out (constant TUNING_DELAY_MSEC in
channelscanner.cpp fixed to 700ms). At least, I got a functional channel file.
I checked the previous CVS qtvision version I used before, and it seems
it cannot scan the channels either (but it used to). This seems really
to be a change in timing in bttv driver hence. With this time-out, I do not
have any scanning problem anymore (with both kernel series).

To sum up, qtvision wouldn't scan neither with 2.6, nor with 2.4.
After increasing the delay, it found some stations (5 ot ouf 7).
With a valid channel file, qtvision works perfectly under 2.4 kernel
(and qtvision does change the norm at startup).
Now, the only remaining problems are :
- norm selection doesn't work under 2.6 as in 2.4 ;
- random crashes of the box (didn't reproduce with 2.6.3 kernel,
but I do not scan for channels anymore either).

>
> One idea I have is that thread locking in the v4l plugin may be broken for
> you, there are a grabber thread and the GUI thread that may want to access
> the device at the same time. That _shouldn't_ crash the box, but may cause
> malfunctions. If you run qtvision in a debugger, you msut never see two
> threads performing an IOCTL on the video device when the app crashes (if
> you happen to only get the app frozen, not the system).

I loolked at source code and put some more traces, and it seems
that qtvision ** does ** fix the secam norm correctly indeed
(after all, it works with 2.4 kernels). But it is not taken into account
by xv.

I found a way to make it work (at least for me) :
changing the aspect ratio / changing the size of the window
is sufficient to make the norm taken into account.
I tracked down the code to XvPutImage (in fact, I only need
to show the channel pannel, this reduces the video widget
and therefore call XvPutImage) : each time this is called,
the norm is taken into account.

However, I didn't managed to see if it was the stop / start
code that makes it work, or only XvPutImage that makes
the xv code work.

Now, I do not know if the problem is from qtvision, Xv or the bttv driver !
I think that as I do channel scanning with the bttv driver,
and as it does works with the right time-out, the bttv driver
seems to work actually. My problem is related to Xv, since
I use Xv to watch (bttv device only show a blue screen
[not of the death !]). In fact, it *may* be a problem from
X11 (4.3.0), which :
1. is rather old ;
2. was compiled against a 2.4.2x kernel (slack 9.1).
Maybe Xv is not 2.6 ready ?
At least it doesn't seem to be a qtvision problem !

> Also, you can try to use overlay (configure in video plugin settings) with
> the v4l plugin now, it should work quite well (but can use some redraw
> improvements) since yesterday. You overlay is enabled if your display
> flickers when the window is hidden/unhidden and you have "artifacts" when
> moving the window.
> If overlay is used, there is no image grabber thread running -> if it
> doesn't crash now, it has something to do with thread race problems.
Overlay would indeed be an interesting test, since I would use bttv
and bypass Xv.
However, I didn't managed to do the test, since the overlay plugin
doesn't appear in the video plugins settings (only mixer and xv
does appear). How can I get these plugins compiled and installed ?

>
> Do you also experience crashes or problems with the xv plugin? If you can't
This is the pluggin I use. It doesn't crash, simply it doesn't fix norm
well with 2.6 kernels.

> scan using the xv plugin, this may be because there is no vbidecoder
> running. Configure it in the plugins dialog.
Same remarks as before : vbi plugin doesn't appear in the config dialog
(CVS 20040214).

CC