Re: some thoughts on /dev/video ...

[Guido Fiala <gfiala@s.netic.de>]

> > You have a bttv card and a dvb card - if you press the xawtv-icon
> > all the drivers should load automatically and it should open the right
> > /dev/video* device. Then you press the gVideo-icon and the same with the
> > dvb-modules. It should work independend from order.
> > 
> > How can we solve this trouble? The most easy would be a different device-major.
>
>What exactly is incombatible between the io calls of the bttv and DVB drivers?
>Grabbing via ioctl with the DVB driver will deliver a single
>uncompressed picture exactly like the bttv driver.

Of course, that one works fine and is currently compatibel.

>
>
>Only read/write and tuning is different:
>
>- tuning 
>  gVideo (or xawtv) could be modified to look for the card capabilities and change
>  the tuning behavior accordingly. (Itīs all open source, knock yourselves out :-)
>
That's exatly the point: 
All applications would have to know about all cards and different
tuning/playback capabilities.
I thought, it was very unlikely, that an application like xawtv will get all
the features of gVideo or even VDR (correct me Gerd, if i'am wrong).

>- write
>  bttv does not have it -> no icompatibility

accepted.
>
>  The IOMEGA BUZ driver has it, but for motion JPEG, so one should just ignore
>  the data if the card cannot handle it

accepted.
>  
>  The Stradis driver has it and at least the playback control io calls are
>  compatible with the DVB driver. Now that the DVB driver understands
>  PES directly this could be made fully compatible.

accepted.

>
>- read 
>  bttv delivers VBI data in /dev/video, that should be changed anyway only to come
>  out of /dev/vbi

Right.

>
>   
>So, what besides tuning is really that incompatible???
>

You are right, there is nothing except tuning & playback.

>I donīt say one could not introduce a new device only for the DVB
>features, but the V4L parts responsible for display on the screen and
>grabbing single pictures are compatible and should stay available
>via the V4L interface.

Maybe we don't really need this, but how would you solve the module-autoloading
& device-name problem?

>The tuner driver of the DVB driver should be compatible with the
>kernel driver and should work with the tuners bttv uses.
>If not, please tell me. I donīt (and never did) use the tuner input of
>the bttv driver much (only for testing) and donīt even have a Bt card
>with tuner installed right now (I really have to get one of those new boards
>with 6 PCI slots ...).

I use the 2.2.14-kernel-bttv and i don't get tuning with the dvb-tuner.o in
xawtv - no station tunes in (autoloading the kernel-tuner.o without options
does work).
Maybe i just did'nt understand it right: if i do "make insmod" in dvb/driver
all these modules load, then i "modprobe bttv" and can start "xawtv
-c/dev/video1" - but how does the bttv.o know about the previously
loaded tuner.o?

If the DVB-S-Card (only DVB-C!?) would have a composite/svhs input, i would
use 2 of them (ha, would be great if it could convert it to MPEG2 ... ok, just
a dream ;-)