[linux-dvb] Re: backwards compatability -was- actual cvs broken?

Michael Krufky mkrufky at m1k.net
Thu Nov 3 01:31:35 CET 2005

Philip Prindeville wrote:

> Hmmm...   I personally have little use for the video functionality 
> that a lot of
> DVB cards come with...  I use them as tuners only, and see the 
> analogue video
> capture capability (from a PAL/NTSC IF source) as unnecessary cruft...
> Probably because the chip already includes it, so the board 
> manufacturers said,
> "well, for $.35 in extra popcorn logic and connectors, it's hardly 
> worth not doing."
> Who actually uses the video capture logic?

*I* do... I live in Brooklyn, NY.  Not all stations that are available 
in analog are also available in digital.

> I've always wondered...   On a multi-function card, does the driver 
> have to handle
> all aspects of that functionality?  Or can you have separate, 
> stand-alone drivers that
> each handle one type of functionality, without them having to be aware 
> of each other or interact with each other?

The answer is a combination of both... Let's take cx88-dvb / 
saa7134-dvb, for example...

The analog drivers work as standalone drivers.  The dvb code relies on 
the glue code in the analog drivers in order to function.  Only the 
"glue code" is aware of the dvb stuff.  With the glue code and dvb stuff 
removed, the analog driver still functions.

> I.e. can tuning and video capture and video playback (for full-feature 
> cards with
> MPEG/AVC decompression) be handled by three independent subsystems and
> drivers?

V4L and DVB are somewhat independent, but not entirely.  So, more or 
less, the answer is yes.

-Michael Krufky

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