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

Allen Edwards allen.edwards at oldpaloalto.com
Tue Jul 22 02:15:21 UTC 2008


Brian Phillips wrote:
> Brad DerManouelian wrote:
>> 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_Adjustmen
> t_Settings
>> *The "garbage" is actually encoded information being sent along with
>> the broadcast like metadata information about the program, closed
>> captioning text, etc. 
> 
> I was a bit skeptical of overscan being my issue for a couple reasons.  1)
> It only happens on a single channel.  2) It doesn't happen 100% of the time
> (but often enough it's worth delving into.).
> 
> I'll look into the scan displacement settings.
> 
> Brian Phillips
> 
This is standard stuff.  I have been watching HDTV for about 6 years and 
this stuff drove me nuts for a long time.  The "garbage" is a data 
signal and it is not there on all broadcasts.  I think it is in the 
analog programs and it comes along for the ride on the DTV transmission 
if not removed by the broadcaster.  Perhaps it is CC data, I don't know.

Anyway, it is perfectly normal to see it and perfectly normal to add 3% 
or so of overscan.  You never noticed it on your analog sets because 
they all have overscan to get rid of this stuff.

Allen


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