[linux-dvb] Display artifacts with VisionPlus (Twinhan) DVB-T card

Matthew Phillips linux-dvb at mattp.name
Sun Mar 13 03:02:59 CET 2005

On 12/03/2005, at 6:59 PM, Robert Schlabbach wrote:
> From: "Matthew Phillips" <linux-dvb at mattp.name>
>> Hello all, I'm having some problems with some Australian DVB-T
>> channels, which I'm hoping someone here might have a clue about. The 
>> SD
>> pictures I'm getting on some channels have, either at the top or 
>> bottom
>> of the picture, a line of blank pixels which sometimes have some white
>> streaks.
> The line at the top is WSS (Wide Screen Signalling) as specified in 
> 300 294. The first half of PAL line 23 is specified to carry WSS, the
> second half live video. Some broadcasters "blacken" this part of the 
> line
> when encoding their analog PAL source for digital broadcasting, others
> (like yours) don't.
> It's not a bug on the receiving end. If you don't want "overscan" 
> areas to
> be visible, you should look for an overscan cropping feature in your TV
> application.

OK. So you mean that broadcasts from digital sources shouldn't have the 
WSS artifacts? That might explain why it comes and goes.

I have a 4:3 TV and most SD here is 16:9, so I don't have much choice 
as to seeing overscan at the top of the screen if I don't want to crop 
the left and right. So the next thing to look at is if I can get MythTV 
to do some cropping.

Thanks for the info,


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