[pvrusb2] Using sysfs to change the input setting and capturing the mpeg stream

[Aaron Newcomb]

Thanks for the update Mike! When I switch to the 2.6.18 kernel I will
give the new controls a try.

On 8/13/06, Mike Isely <isely at isely.net> wrote:
> On Mon, 31 Jul 2006, Aaron Newcomb wrote:
>
> > Thanks, Mike.
> >
> > I think my problem was trying to use vi to edit the file instead of
> > just doing ...
> >
> > echo "s-video" >cur_val
>
> Yeah, editing the file is not always a good idea because the editor may
> try to move the "original" version to a backup name with link/unlink and
> then try to create a new file.  That of course isn't going to work in
> sysfs...
>
>
> >
> > Once I did that it worked fine. However, I get terrible static sound
> > in mplayer when I do that. I also get it when I use cat to capture the
> > video. I am not using audio at this point so it's not that big of a
> > deal, but is there a way to get rid of that static? Also, does anyone
> > have any tips on sharpening up the video? I am guessing my options are
> > probably limited here because of the analog signal.
>
> I presume you just don't have the audio connected when you are capturing
> your desktop graphics, right?  In that case I would expect the audio to be
> merely silence not noise.  Audio input with s-video (and composite - it's
> the same jack) should work just fine; I've done tests with that in the
> past and others here haven't reported problems.  So I'm puzzled by the
> static.  However, as suggested in another reply, you can just mute the
> audio in the usual way when you do the capture.
>
> As for tweaking the video quality, there are some possibilities, but you
> need to build the (standalone) driver a little differently or use the
> driver as it is included inside V4L or in the 2.6.18 kernel.  Recently the
> control of the cx23416 mpeg2 encoder chip was reimplemented in a new v4l
> module, called cx2341x.  The idea is to put this common code in one place
> and then all drivers (blackbird, ivtv, pvrusb2) can just use the common
> code.  With this new module also comes some new controls that manipulate
> various types of digital filtering possible in the encoder chip.  So,
> basically you need to build the pvrusb2 driver such that it uses the new
> cx2341x module.  Once you do that, then a bunch of additional controls
> show up in V4L (via new control IDs) and in sysfs.  I've played with these
> controls a bit here, but I don't really know a lot how to use them.  All
> I've managed to do so far is make the picture worse :-)
>
> To build the pvrusb2 driver in a way that it can use cx2341x means that
> you have to build it in an environment where the new cx2341x module is
> present.  You can do this using any of the following strategies:
>
> 1. Just use the pvrusb2 driver included in the current v4l-dvb mercurial
> snapshot.
>
> 2. Or, just use the pvrusb2 driver included in the 2.6.18-preX kernel.
>
> 3. Or, compile the stand-alone driver against 2.6.18-preX
>
> 4. Or, compile the stand-alone driver against a recent v4l-dvb mercurial
> snapshot.
>
> Whether the pvrusb2 driver you use is from the kernel, from Mercurial, or
> (recent) standalone is not the issue - in all cases the needed logic to
> communicate with the cx2341x module is present.  They are all really the
> same driver (with some tweaks in each case).  The trick is to build the
> driver within an environment where the cx2341x module is in fact, present.
> That means you have to build it against a 2.6.18 (or later) kernel or you
> have to build it again a v4l-dvb repo.  But of course, with those two
> choices you don't have to even use the standalone driver since in both
> cases there's a pvrusb2 driver version already embedded.  Clear as mud?
>
>    -Mike
>
>
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-- 
Thanks,
Aaron Newcomb
http://www.thesourceshow.org