[mythtv-users] Flickering lines at the bottom of TV

Allen Edwards allen.edwards at oldpaloalto.com
Tue Jul 22 01:26:13 UTC 2008


Brad DerManouelian wrote:
> On Jul 21, 2008, at 5:24 PM, Brian Phillips wrote:
> 
>> Hello,
>>
>> I have a problem where my recordings on one of my channels of analog  
>> cable
>> have a flickering line at the bottom (and sometimes top) of the  
>> screen.
>> It's mainly the bottom.  I've got a screenshot here:
>>
>> http://www.et.byu.edu/~bphilli7/pics/law.png
>>
>> I don't know how to describe what it is, but I was hoping someone on  
>> the
>> list could tell me what causes it and what I can do to fix it.
>>
>> It only happens on one of my 20 or so cable channels I get.  I was  
>> thinking
>> it might be a tuning issue (maybe fine tuning the frequency for that  
>> channel
>> could fix it) or something in that same vein.  Anyone know what  
>> causes that
>> flickering line?  It's not always there.  It's just always there on  
>> that
>> channel.
> 
> It's being broadcast that way. There is nothing to fix on your end.  
> Usually a television's overscan will hide this sort of thing but since  
> you're displaying the entire video, you're getting the garbage* edges  
> as well.
> For info on Overscan here: http://www.mythtv.org/wiki/index.php/Overscan
> 
> To hide this, you can play back your videos 1% or 2% larger than they  
> actually are (whichever works for you) or you can crop your recordings  
> by transcoding them with crop settings.
> http://www.mythtv.org/wiki/index.php/Overscan#TV_Playback_Overscan_Adjustment_Settings
> 
> *The "garbage" is actually encoded information being sent along with  
> the broadcast like metadata information about the program, closed  
> captioning text, etc.
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> 
One of the really nice things about mythtv is the ability to set the 
size on playback to +3% to get rid of these lines.  I have had dedicated 
decoder boxes that could not do this.  Anyway, it is in one of the setup 
menus in myth under TV playback.

Allen



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