[mythtv-users] Cropping with PVR-150

Jim Stichnoth stichnot at gmail.com
Wed Oct 1 18:40:49 UTC 2008

On Thu, Sep 25, 2008 at 9:59 AM, Jim Stichnoth <stichnot at gmail.com> wrote:

> I recently installed a Hauppauge PVR-150 to complement my two HDHomeRun
> boxes, with the s-video input connected to a DirecTiVo box.  I have closed
> captioning enabled in the mythtv setup, which works great, except that the
> PVR-150 seems to be cropping around 10 lines from the top, and inserting a
> horizontal black bar at the bottom.  Doing "cat /dev/video > /tmp/foo.mpg"
> and then playing foo.mpg with xine or mplayer also shows the black bar (as
> well as a smaller vertical black bar on the left), and foo.mpg is at 720x480
> resolution.
> If I first execute "v4l2-ctl -b off", then the bottom black bar is no
> longer there in foo.mpg (though the small black bar on the left is the
> same).  I'm guessing that the PVR-150 and/or ivtv are helpfully stripping
> the VBI information.  But this is not really necessary since I already have
> global settings to deal with the flickering VBI line in the picture that the
> HDHR picks up from digital SD broadcasts.
> Is there a way to get rid of this bottom black bar and also keep closed
> captions?
> I'm running MythDora 5.  I'm not quite sure how to figure out what version
> of ivtv I have.
> Jim

I took a couple of screen shots to show the problem more clearly.  I paused
the input source (an SD DirecTiVo), then ran either "v4l2-ctl -b cc" or
"v4l2-ctl -b off" to turn closed captioning on or off, and then captured a
frame using xine.  If you flip back and forth between the two images, it's
clear that the first several lines are being cropped and everything shifted
up when cc is enabled.  It's also interesting that even with the uncropped
picture, the VBI stuff has apparently already been removed.  If I had to
guess, I would say that VBI removal is being done twice when cc is on.  (I
would prefer that VBI were not removed at all, so that MythTV overscan or
whatever could be applied consistently to all inputs.)

cc on: http://www.flickr.com/photos/37377999@N00/2905480460/sizes/o/
cc off: http://www.flickr.com/photos/37377999@N00/2905480878/sizes/o/

Any ideas on this?

On a barely related note, I was also experiencing the PVR-150 "tinny audio"
problem on many recordings, but the various tweaks suggested on mailing
lists weren't fixing it.  (I was trying to add the extra commands to my
channel changing script.)  I finally realized that mythtv doesn't start
capturing from the PVR-150 until after the channel change script completes.
The solution was to run a background command from the channel change script
that delays a few seconds and then executes the command.  In my bash script,
the last line is this:
        ( sleep 5; v4l2-ctl --set-audio-input 1 -d /dev/video0 > /dev/null
2>&1 ) &
I'm sure there's something similar for people using perl scripts.

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