[pvrusb2] WinTV PVR USB2 No video

[Mike Isely]

On Tue, 21 Apr 2009, Tamas Szecsi wrote:

> Hi all,
> 
> I am trying to use a Canon VC-C4 analogue videocamera in Linux 
> (Ubuntu). I have used it with a Belkin frame-grabber in Windows but 
> there seems to be no Linux support for that. So instead I bought a 
> WinTV PVR USB2 (as there appears to be an excellent support group and 
> discussion forum for it).
> 
> I have connected the camera to the SVideo input of the WinTV, in the 
> Windows WinTV programme I set up the SVideo input for PAL_BGHIDK (I 
> live in Ireland). Then I tested the setup in Ulead Videostudio (for 
> Windows), it was abled to capture the video, so everything seems to be 
> working fine with Windows. However, I have problems with the Linux 
> installation.
> 
> The 'mplayer /dev/video0' command only produces a snowflake-like 
> image, as if I am using a channel without a signal on it. The 'cat 
> /dev/video0 >test.mpg' command does produce a video file, but again, 
> when watched on mplayer it is still the same 'empty' video.
> 
> There seems to be a conflict between the 'Detected format' (NTSC-M) 
> and the 'Specified standard' (PAL-BDGHI). Any help would be 
> appreciated. I have attached below the 'standard' printouts for the 
> device that appear in most mailing lists.

   [...]

My first guess is similar to yours - a mismatch of the video standard.

When you cat from /dev/video0 (or use mplayer), you're not using the 
actual V4L API.  That itself is not really a problem, however it means 
that you're not doing anything to configure the driver for things like, 
for example, the video standard.  It's entirely possible that the wrong 
video standard was used.  However I'm not 100% because if you have a PAL 
vs NTSC foulup, you'll generally see *something* though it won't be 
usable.  But you're describing snow which suggests no signal at all.  As 
for the cx25843 log messages, the "detected format" doesn't carry any 
meaning if there's no signal.  And the fact that the specified standard 
looks right means that this aspect seems not to be the problem.

Another (very likely) issue is that you don't have the right input 
selected.  Again, unless you did something to set up the driver before 
cat'ing from /dev/video0 then the driver is just going to use its 
current settings.  And certainly in that case the driver defaults to the 
RF tuner, not the S-video input.

The way to solve this is through the sysfs driver interface.  Read here:

http://www.isely.net/pvrusb2/usage.html#sysfs

Then look at ctl_input/cur_val and ctl_video_standard/cur_val.  You can 
do all of this from a simple shell.  Check that those are correct (and 
if not, correct them).  Then try mplayer again.

If you run a V4L app, like MythTV, xawtv or the tv-viewer app I had 
mentioned a short while ago, then you don't have to worry about the 
sysfs interface.  In those V4L cases, the controls all are available via 
the V4L API, and your app will take care of it.

Let me know if that helps.

  -Mike


-- 

Mike Isely
isely @ pobox (dot) com
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