[linux-dvb] Re: V4L issues with linux dvb driver

[Michael Hunold <hunold-ml@web.de>]

Hello Billy,

to make a long story short: "linuxtv-dvb-1.0.0-pre1" and the so-called 
DVB "head" or "newstruct" drivers are v4l1 drivers.

The CVS "dvb-kernel" driver is the new *v4l2* driver, which does not 
have the problems you mentioned. YUYV byteorder is completely disabled, 
capture performance problems should be gone, because I use Gerd Knorr's 
"video-buf" capture buffer abstraction. Because of that, the performance 
should be equal to the bttv / saa7134 driver.

>   1. Please do not do format conversion in software.  I can easily
> support UYVY in my application, and I need to do this for the rivatv
> cards (which also currently converts in software, leading to more bug
The original problem was, that the bttv driver first only supported YUYV 
byteorder, so all applications assumed the byte order to be YUYV.

But the saa7146 has a native UYVY byteorder and a hardware bug, which 
prevents it from delivering YUYV at all.

> reports about poor performance).  VIDIOCMCAPTURE  should fail on these
> boards when asking for YUY2 images (VIDEO_PALETTE_YUV422).
>   2. The VIDIOCSPICT ioctl currently always fails when asking for YUY2
> images.  By the comment above, this should only happen with chips below
> revision 3.  To support other drivers, my code must call this ioctl
> before starting capture, so it would be nice to make this ioctl return
> accurate information.
>
>   3. By the code, the VIDIOCMCAPTURE ioctl will fail if you ask for
> frames in UYVY format, which will make my support of it useless.  :)
Although the code is based on my original saa7146 driver, I won't change 
it anymore. "dvb-kernel" is the basis for the upcoming 2.6.x kernel and 
it can be compiled under 2.4.x as well.

If you encounter any more bug reports regarding the "linuxtv.org" DVB 
driver, please encourage the users to try the "dvb-kernel" driver from 
the project's CVS (remember: it can be compiled under 2.4.x as well) and 
use the benefits of v4l2.

>   Thanks for your time,
>   -Billy
Is your application v4l2 aware?
Or do you rely on the compatibility layer?

I'll have a look at this later today and test the "dvb-kernel" driver 
with "tvtime" and come back to you later.

CU
Michael.




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