On Thu, Mar 03, 2005 at 12:25:32PM +0100, Martin Husemann wrote:
> On Thu, Mar 03, 2005 at 09:29:42AM +0000, Dave Tyson wrote:
> > IMHO the only practical approaches are (3) use V4l2 or (4) a separate API and 
> > a compatability layer. Reusing the bktr API (2)  is probably a bad thing as a 
> > lot of the satellite PCI cards have quite a different set of requirements .
> 
> If I understood a co-worker correctly, v4l only does handle analog receivers
> and linux uses something else for dvb. This sounds ... wrong.

v4l assumes all devices output a clean, uncompressed video stream. CMIIAW,
but dvb cards output (encrypted?) MPEG streams.

In fact, webcams often compress data, too, in order to raise the max number
of FPS they can squeeze through a USB 1.1 pipe. Since these devices are v4l
devices, this means decompressing takes place in the kernel. This sounds
just as wrong to me.

However, if every (class of) device outputs its data differently, the point
of having an abstract hardware interface decays rapidly - so there's a 
tradeoff to be made.