[linux-dvb] V4L interface to the MPEG stream?

[Ed Wildgoose <Ed@Wildgooses.com>]

I'm looking at whether my DVB-T card can be easily integrated with 
MythTv (a pvr program somewhat like VDR)

MythTv takes as input, either an analogue v4l source, or a v4l2 source 
from a hardware MPEG encoder.

Leaving aside whether VDR is an easier/better option for the moment, I'm 
 out of my depth in determining whether I can make the DVB card pretend 
to be either of these interfaces

I have a full card with decoder, so I get a /dev/video1 v4l device (I'm 
under 2.4.20 with the standard v4l checkout from CVS).  However, Mythtv 
is calling this line of code and failing with "invalid parameter":

  if (ioctl(fd, VIDIOCMCAPTURE, &mm)<0)
      perror("VIDIOCMCAPTURE0");

and this is actually code out of nuvrec, so although I haven't tried, I 
assume that nuvrec would also fail to record from this v4l interface.

Can anyone please explain what this line does and why it would fail with 
the error (presumably previous lines of code would help, but I don't 
want to send great wads of code needlessly).

The obvious thing would be height and width and I am setting the params 
to be 720x576 which appears to match the native output from the v4l device?

Secondly, mythtv accepts input from a v4l2 device in MPEG 2 format.  Is 
this possible under v4l2 then?  Does the input not have to be 
straightforward uncompressed yuv type output?

So can the latest v4l2 driver for the DVB-T card do this as well?  ie if 
I upgrade my kernel to 2.4.20 with the v4l2 patches and grab the 2.5 
kernel branch of the driver will I get a /dev/video1 device which can 
spit out MPEG 2?  Does this actually even make sense...?!!

Thoughts appreciated

Thanks all




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