[mythtv-users] IVTV issues (video scrambled looking)

Brian Wood beww at beww.org
Sat Jun 3 16:24:23 UTC 2006


On Jun 3, 2006, at 8:33 AM, Mickey Chandler wrote:

> At 09:05 AM 6/3/2006, Brian Wood wrote:
>> Do you mean that the file plays OK someplace? If it plays properly
>> with any player on any machine it most likely means that the file is
>> OK, though some players are more tolerant of errors than others.
>> Most Myth installations have xine or mplayer for playing DVDs etc.
>
> No, the file doesn't play properly anywhere.  However, instead of the
> static, I'm not seeing anything for the video.  I've put up a 1
> minute grab of /dev/video0 to:
> http://mickc.whizardries.com/blog/wp-content/uploads/2006/06/out.mpg
>
>> You could turn things around as well, get a known good mpeg file and
>> import it into Myth and see if it plays OK.
>
> It plays all of the previous recordings just fine.  I can't get new
> ones, though.
>

Very strange. The mpeg actually seems to be good, by that I mean it  
has accurately recorded what it was asked to record, and it plays  
back without errors. In other words whatever is causing the problem  
is ahead of the mpeg encoder.

There seems to be four bands in the horizontal blanking that look  
almost like the old system of encoding audio into the H blanking of  
PAL channels, but no information seems to be in the channels, they  
are just square waves. It looks like the capture card is having  
trouble locking, perhaps because of this anomaly in the blanking.

The information is all there, just not locked.

Is it possible that this signal is being encoded in some way as to  
prevent recording ? I know you said it played OK on a TV set but that  
might not mean anything. It almost looks like Macrovision, but in the  
horizontal not the vertical, and a Macrovision signal will look OK on  
a TV but won't allow a VCR to get a good servo lock.

At this point I would say the video signal is non-standard in some  
way that prevents the capture card from locking, but I really need  
more information.


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