[mythtv-users] Underscan in playback and recording, driver issue?

Michael T. Dean mtdean at thirdcontact.com
Mon Sep 25 06:21:42 UTC 2006

On 09/24/06 22:54, Carl Lewis wrote:

>David McKenzie wrote:
>>The problem is that recordings and live TV using the PVR-150 doesn't 
>>fill the screen completely

>>Has anyone seen this before or can offer a resolution? Right now it is
>>the only thing from letting me switch over to Myth completely.
>David, I've been seeing the same thing in Australia, with ABC in
>particular. I run a 100" screen (projector :-) with no
>overscan. The affected channels/programs have about a 2" vertical
>stripe/black-bar down one or both sides.
>I've only  noticed it since setting up a border around the screen :-/
>so I've no idea when it started.
>Same as you I've looked at the recordings themselves and they contain
>the vertical space.

Because the recording device was designed for use with a system that 
/requires/ overscan.  I.e. NTSC and PAL were designed such that display 
devices would overscan the image to cut off black/green/rainbow bars, 
static, jagged edges, and any other "ugly" attributes of the image 
allowing the user to see only pretty and without requiring significantly 
advanced technology (remember also we're talking about technologies that 
are over 50 and almost 40 years old, respectively).

That means, it's not a driver issues, but an encoding system issue (and 
we're talking the encoding that comes before the PVR does its 
encoding--garbage in/garbage out and all).  So, if you don't want the 
edges, overscan the image to get rid of them--make your display device 
work as the designers of NTSC/PAL intended.


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