[mythtv-users] MythTv component out HOWTO
adeffs.mythtv at gmail.com
Mon Apr 10 20:23:06 UTC 2006
On 4/10/06, Steve Skarda <steveskarda at gmail.com> wrote:
> Know problems:
> -There is bad overscan. The people that know a lot about video say that is
> due to the TV. That may be true but there is no way to adjust it since the
> TVStandard "HD1080i" overrides all modelines from what I can tell and there
> is no overscan setting in nvidia-settings when 1080i is selected. A
> workaround to this problem is to set the gui size in the MythTV general
> settings. I had to cut more than 100 pixals out of my picture for both
> height and width which makes me believe it is a nvdia problem (or my
> problem) more so than the TV. Then check play video at the size of gui.
> Others have complained about artifacts in the screen but I don't see
> anything so this works for me.
Overscan is purely a TV issue. Each TV will have a different level of
overscan, 5% per side is about the average. This means that the
picture your tv gets from your video card will be cropped the same
amount as what it gets from a DVD player or cable box, etc.
Overscan causes problems with sources that expect the viewer to be
able to see to the absolute extents like on a properly set up computer
monitor. Myth lets you fix the overscan issue with the menu by letting
you set the height width and horizontal and vertical offset so that
you can "place" your menu properly on your TV. Myth also has an option
to use those settings for displaying TV. Myth also has a percentage
based system for doing the same but just for video (ie not the menu).
The other option is to go into the TV's service menu and properly
adjust the overscan. the minimum overscan value per side is 5% for
This means you want at least 5% of each edge of the incoming video to
NOT show. This is to block edge artifacting, etc. It is a holdover
from FILM. Film hates edges, edges don't play nice chemicaly. Film
apertures were based on 5% changes, thus the minimum value for NTSC.
But HDTV doesn't need this. In the HDTV digital realm there is no such
thing as overscan. 1920x1080 is 1920x1080 (which is 1080p) except when
its 1920x540 (which is 1080i). 1280x720 is 1280x720. The video that is
broadcast is meant to be displayed in all its glory, so get rid of the
overscan. Do it in your TV's service menu if you can, or hire an ISF
technician to do it for you. If not, even if you "correct" for
overscan in Myth your still not seeing the full image in its true
glory, your seeing something like 1884x1022, etc.
> -I have interlacing artifacts. They are minor, only a line or two at the
> top of the screen during scenes with significant motion but it is annoying
> none the less.
which is why interlacing sucks.
> -I have read on nvnews that the quality coming from the component out is
> bad. I have nothing to compare to so I don't know if that is true. (I am
> planning on purchasing a front projector with DVI so I am not going to
> bother buying a transcoder to find out). The poster stated that switching
> to the transcoder made a huge improvement and they could see text for the
> first time. I will say that I can't read text on my desktop on my
> television so there may be some truth to that. Here is a link to the post
> if you are considering buying a 6200 for this capability.
I found that using the 9A60 my 720p output via DVI is much better.
I've yet to try 1080i through DVI, but I'll assume it will look even
better than through the 9A60. Which is a great product, and looks
great, but not as good as DVI, and it shouldn't.
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