[opendtv] Re: Overscanning on LCD TVs
- From: Tom Barry <trbarry@xxxxxxxxxxx>
- To: opendtv@xxxxxxxxxxxxx
- Date: Thu, 05 Nov 2009 13:29:17 -0500
I also have a Sharp DLP projector connected to my computer using VGA
input. And it also seems to adjust to the size of the screen without
eating the edges. Though sometimes I have to switch it to another input
and back to get it to do this.
Maybe some devices just assume VGA is computer and thus does not want
overscan. ?? Dunno.
I remember with my old 1080i Toshiba RPTV CRT I had to get the service
manual and do serious service mode changes to deal with overscan issues
to use it with a computer. But that was almost 10 years ago and I
thought things were different now.
I don't think overscan really has any useful function in a digital fixed
pixel display world. Why send any part of a picture that is not
expected to display? Digital TV transmission knows exactly where the
edge of the picture is, to the single pixel. And it does not transmit
anything for vertical or horizontal blanking. That's an artifact of
CRT's and can be provided by the display or STB after decoding if
required but certainly should not be part of the picture.
Overscan is really just a legacy bug now.
- Tom
nicholas kocsis wrote:
> I make no pretence of being 'expert' in this subject. I do have the same
> complaint with my Samsung DLP 56" RP display (720p) bought circa 2002-2003.
> The display loses at least 3" of display at each edge. My sources can be OTA
> or satellite receiver output with the same overscan attributable to the
> display monitor itself. Of late the overscan is decidedly annoying on some
> programming where text overlays are 'chopped'.
>
> I did notice that when in a showroom (a year or two after buying) watching
> side by side the same program on different TV makes. Some did display a
> normal scan while others had noticeable overscan.
>
> It leaves me to wonder whether overscan was intentional by the designers of
> early TV digital displays to avoid some potential display problems.
> ----- Original Message -----
> From: dan.grimes@xxxxxxxx
> To: opendtv@xxxxxxxxxxxxx
> Sent: Thursday, November 05, 2009 12:36 PM
> Subject: [opendtv] Overscanning on LCD TVs
>
>
> We have a large amount of consumer grade Sony Bravia televisions in our
> facility. It appears that all of them overscan the picture, despite setting
> "overscan" to normal in the menu. Adjusting overscan to 1 or 2 makes it even
> worse. The only sources I have been able to confirm are on the HDMI inputs
> and often using HD-SDI to HDMI converters but I have also seen it with DVI
> sources. I plan to test with BD as well.
>
> So my question is, is overscanning typical with consumer TVs? I thought
> that it that current LCD TV's used all 1920x1080 pixels.
>
> I should also probably note that most of the signals are 720P.
>
> Because of a deal with Sony, I don't have too many other display
> manufacturers to test up against, thus the question to the display experts
> here.
>
> Dan Grimes
>
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