[mythtv-users] Commercial Flagging, what are the best

Kevin Kuphal kuphal at dls.net
Wed Dec 21 15:06:18 EST 2005

Kevin Kuphal wrote:

> David Rudder wrote:
>> This is a pretty off-the-wall suggestion.  Is there anyway to detect 
>> V-Chip signals?  I know within the US, all broadcast and cable shows 
>> have a V-Chip signal, but it's turned off during commercials.  This 
>> would be a 100% reliable way of detecting commercials, but I have no 
>> clue whether the signal could be picked up by myth.
>> I would be ironic to have something good come out of V-Chip, eh?
> Upon further investigation, it seems like it would be trivial to 
> extract the information into Myth using the IVTV VBI support.  Right 
> now Myth will extract the CC information out of field one of line 21 
> (see line 1634 for avformatdecoder.cpp).  The XDS information is 
> stored in field two of that line.  I think using buf[3] and buf[4] 
> would yield the XDS packet V-chip packet based on the information in 
> the other link I posted.
> Decoding that is easy based on the documentation and then it is just a 
> matter of passing that into the right structure that the commercial 
> detector can use.  I may have to see about getting my PVR-150 to 
> decode VBI/CC packets and see if mabe I can get this to work...

In looking further, recent SVN changes have the skeleton for XDS parsing 
but nothing is done with the data.  My PVR-150 is putting data into 
/dev/vbi so I think my backend is set up for capturing.  This may be my 
Christmas project to see if I can properly decode the XDS V-chip 
information at least in debugging output to see what it says.


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