[linux-dvb] Re: overlay-problem -> pci-latency

[Michael Hunold <hunold@convergence.de>]

Hello Guido,

On 15.02.2004 13:03, Guido Fiala schrieb:
> Me (and someone else) noticed a problem with the overlay becoming black or 
> turned of if an other window is partially before the overlay and clipping 
> rectangles are used.
I once introduced a bug that cause this, but this has been fixed for a 
long time now. (I just confirmed this with a fresh CVS driver)

> I experimented with PCI latency for the saa7146 and found out, that using 
> larger latency increases those problems and using smaller latency reducing 
> it.
PCI latency usually affects the display quality on poor PCI 
implementations, like on VIA chipsets. There, PCI to AGP transfers (from 
the dvb card the the gfx adapter) are horribly slow, so you'll notice 
dropped pixels on the right side of the picture. The problem also 
depends on the picture size and the screen depth (ie. more pixels to 
transfer, the more likely the problem happens)

> Of course very small latencies are not suitable too, at a latency of 16 the 
> overlay functions pretty stable, only if the obfuscation is at the right end 
> of the overlay it is still vanishing.
Hm, can you take a screenshot of the problems you are experiencing?

> Not sure but in system log sometimes messages like this appear, but not 
> directly if the overlay is disappearing:
>
> Feb 15 12:46:02 [kernel] saa7146: ==> calculate_video_dma1_overlay: illegal 
> values: y: 0  h: 0  d: 16  b: 4096  base: -536870912
From this output I conclude that you are using an "old" DVB driver (ie. 
not the dvb-kernel CVS driver or an 2.6 kernel), right?

I'm sorry, but I don't debug video problems on that version any more, 
because too much has changed on the way to the current driver version. 
Because it's going to fade away slowly, we should debug and fix the 
driver for a recent driver.

> Is this a chipset or a driver bug?
> (Have a Lex BN815 mainboard which has an i815 chipset.)
Intel chipsets were always rock-solid for me. So it's likely a driver bug.

> other remark regarding the overlay:
>
> while grabbing an image or using xv in an overlay-displaying application (as 
> my kvdr) the overlay is turned back on by the driver accidently, therefore 
> one needs to set it to a very small size that it does'nt disturb the 
> xv-frame. At least i have no other idea what to do with the overlay if i 
> don't want it to be seen.
Sounds bogus, too, or I did not understand the problem. 8-(

Anyway, I'd like to ask you to try the "dvb-kernel" driver from CVS or 
the recent official release tarball.

I remember that "kvdr" is Video4Linux-1, not Video4Linux-2, right?

In that case, all stuff will go through the compatibility layer, but 
that works for most programs. If there are problems with that, I'll be 
glad to help.

CU
Michael.


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