[linux-dvb] V4 API suggestion [was:dec2000-t (and perhaps dec3000 and dec2450) playback]

[Alex Woods <linux-dvb@giblets.org>]

> I wrote some code to convert mpeg2 pes packets (or a program stream)
> into pva packets so that a hauppauge/tt dec2000-t can playback it. The
> output seems to be correct. But as I'm not working on the dec2000-t
> playback thing anymore and I got no response from Alex, who wrote the
> ttusb-dec module, I post the code here just in case anyone wants to
> finish the job.

Thanks Ulf.  Sorry for not getting back to you, but something gave me the 
impression that I'd hear something more from you, and after a couple of days 
it all slipped my mind - an all too common occurance ;-)

Anyway, to move on the V4 suggestion - hope it's not too late.  In case you 
don't know, the USB DEC devices talk in PVA, which is nasty of them, but the 
format is quite well supported in userspace applications.  In order to comply 
with the V3 API the ttusb-dec driver is converting this PVA to TS in kernel 
space.  This feels quite wrong to me.  IMHO the driver should publish its 
format abilities for both input and output through the API so that things in 
userspace can decide how best to use.  It seems crazy to be converting PVA to 
TS if all you're going to do is pipe it straight to mplayer which handles PVA 
just fine.

I know I might be going out on a limb here, since the DEC is currently the 
only device using a format this far from the DVB standard.  Am I right in 
thinking that the ttpci drivers do some data munging, albeit to a lesser 
degree, though?  I think providing a userspace library for application 
developers to use is the best way forward, similar to the way the ALSA 
project do.  I'm sure it would help projects like VDR to keep up to date in 
terms of the drivers they use too.  IMHO, providing backward compatibility is 
going to become an increasingly important factor as DVB uptake increases, and 
a userspace library would be a good start to achieving this, and the right 
place to do it.

I'm aware that manpower is a big issue for this project (very aware, since 
this is something I do in my spare time).  I'd really like to contribute to 
development of the DVB core, but I'm feeling like a bit of an out of touch 
with the project, probably because of the weirdness of my driver (USB and 
PVA).  There are also holes in my understanding of DVB technology, for the 
same reason I think.  Still, now would be a good time to throw me a bone, 
since I'm in the mood for some coding.

Cheers,
Alex


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