[linux-dvb] Re: dvb driver corrupts video memory?

[Michael Hunold <hunold@convergence.de>]

Hello Olaf,

> Here's a bug report against the DVB driver, all versions.
This means the official DVB driver, the DVB CVS driver, but not the 
dvb-kernel driver, right?

> XFree86 4.2.99.1
Looks rather old to me, 4.3 is out half a year now. But this shouldn't 
matter.

> It seems like xawtv always uses the "Matrox G-Series Backend Scaler"
> device for video output (in overlay mode). This comes with the X
> server. 
You can enable or disable the "v4l" module in your X config. If loaded, 
it will present your dvb-card as a "Xv adaptor". The main advantage is 
that the X server takes control over the window redraw handling, ie. 
screen refreshing is minimized.

Do you load this module and use it?

A quick way to check if it's in use is to open "xawtv" and point your 
mouse pointer on the window close button of the main window, so that a 
popup window is opened. If the popup above the video causes the whole 
screen to be redrawn, then the "v4l" module is *not* in use.

From your descriptions later on I assume that you're not using it. 
Xawtv will use the backend scaler of your Matrox for the "grabdisplay" 
mode only.

> It can use either one of the two video devices as input and
> all seems to work fine.
Ok.

> However, with certain things done to the xawtv window, the video
> output suddenly gets distorted.
> The distortions look like vertical stripes, 1-10 pixels wide, of the
> video window getting reordered. The pattern always changes, sometimes
> it changes with channel switches in vdr or more window manipulations
> (including getting fixed). The OSD is affected too.
Can you make a screenshot of this and put it onto some webpage?
(If not, please sent the pictures to me in private)

> Also with the newer version, in "corrupted mode" some X applications
> misbehave, e.g. Mozilla shows black bars instead of characters. This
> may be the problem described in the mplayer docs where an application
> directly writing into video memory corrupts the X server's pixmap cache.
Hm, from your descriptions I assume that you're using the plain overlay 
mode without the "v4l" X module loaded.

> Since the problem only occurs with DVB (not with only the bttv driver,
> but it persists after unloading the DVB driver, indicating that indeed
> some memory gets corrupted), and somewhat depends on the DVB driver
> version, I assume the bug is in the DVB driver.
This really might be. Unfortunately, the bug is in the saa7146 video 
driver parts. As I already have mentioned in other mails, these parts 
come from a forked version version of my saa7146 driver and I don't 
maintain these parts anymore (although that I admit that this is a 
serious bug).

So I'd like you to try the "dvb-kernel" CVS driver. You can easily check 
out, compile and use it without installing it (so you don't corrupt your 
working installation). It features the new saa7146 Video4Linux-2 core 
that I have developped the last years (and which is shared between a 
couple of dvb and non-dvb drivers).

Instructions are in "build-2.4/README" in the "dvb-kernel" CVS repository.

This is the version that's currently in the 2.6 kernel series. If you 
can reproduce the bug there, I'll give you any help I can to track this 
bug down and I'll fix it.

> Olaf
CU
Michael.



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