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What is the typical modern overscan?

post #1 of 33
Thread Starter 
If you're creating content for modern plasmas and LCDs, do you still use the old "10% height" title safe guidelines? I don't care about supporting CRTs with my project, and I could use all the vertical space I could get. Would I still need to leave a 54-pixel margin at the bottom of a 1080p image? Could I afford to run a little closer?
post #2 of 33
From the 'overscan' wikipedia article:
On LCDs driven from a digital signal, no adjustment is necessary because all pixels are in fixed positions. Thus all modern computers can safely assume that every last pixel is visible to the viewer.

You could go up to as much as 1 or maybe 2% to be safe, as some manufacturers still induce some over-scan on digital displays. Although this is always much much less than old CRT's.

I wonder how much longer until sports broadcasts stop putting the scoreboard a 1/4 of the way into the screen?
Annoying!
post #3 of 33
Thread Starter 
I think the Wikipedia article is a little over-optimistic. It's my understanding that modern LCDs and plasmas ship with overscan by default to prevent users from seeing garbage data along the edges of HD broadcasts. They have the ABILITY to to 1:1 pixel mapping, but it's not enabled by default. But what that default overscan value typically is... that's my question!

I've seen references I don't necessarily trust along the lines that 3% overscan should be a safe allowance for modern sets, which would be about 16 pixels along the bottom of a 1080p display if I'm doing my math right (that's another question: is my math right?).
post #4 of 33
Don't confuse the about 10% overscan of firmware conterolled present to emulate the origional CRTs,( which is now able to be disabled in almost all/if not all current generation TVs) with the about 1-2% of overscan preseent to insure that the actual edge of the screen image is underneath the TV's Bezel.
On some models you can remove the small percent of % and there is no harm in doing so I have done this on my LCD TV but need to adjust it again because one of the networik channels often has their screen underscanned by less about 1%.
Since the TV stations are very aware of the fact that TVs have overscan they normally have meaningfull content near the edges of the video frame so you incrase the physical size of the meaningfull TV content by leaving overscan enabled.
post #5 of 33
On modern LCD and plasma HD displays if overscan is enabled, its typically 2.5% at each edge, for a total of 5% lost horizontally and vertically. For 1920x1080 format with 1080 pixels high that would amount to cutting off 54 pixels total, 27 top and 27 bottom.
post #6 of 33
Thread Starter 
Quote:
Originally Posted by walford View Post

Don't confuse the about 10% overscan of firmware conterolled present to emulate the origional CRTs,( which is now able to be disabled in almost all/if not all current generation TVs) with the about 1-2% of overscan preseent to insure that the actual edge of the screen image is underneath the TV's Bezel.

So you're saying modern sets max out at 2%? It's important I don't get this number too low, i.e. if there's a major manufacturer that defaults to 2.5% or 3%.
post #7 of 33
Thread Starter 
Quote:
Originally Posted by Joxer View Post

On modern LCD and plasma HD displays if overscan is enabled, its typically 2.5% at each edge, for a total of 5% lost horizontally and vertically. For 1920x1080 format with 1080 pixels high that would amount to cutting off 54 pixels total, 27 top and 27 bottom.

OK thanks, I just want to verify the math. On the BBC graphic in the Wikipedia article, the "10% overscan" translates into 5% per side, so what you're saying is that by that definition of overscan, modern displays still have a 5% overscan? If so, that's disappointing...
post #8 of 33
Quote:
Originally Posted by Joxer View Post

On modern LCD and plasma HD displays if overscan is enabled, its typically 2.5% at each edge, for a total of 5% lost horizontally and vertically. For 1920x1080 format with 1080 pixels high that would amount to cutting off 54 pixels total, 27 top and 27 bottom.

That's sounds about right. When I adjusted by LCD with the AVS HD709 disk 2.5% seemed to be the margin.
post #9 of 33
Thread Starter 
OK thanks. I think I have my answer!
post #10 of 33
Many HD sets however have a way to select zero overscan with 1080i/1080p sources.
I do that on my Samsung LCD and Panasonic plasma for HD sources, and only enable the 5% overscan display mode for SD channels that have some noise at the top of the image.
post #11 of 33
It's important to understand that with ATSC digital transmissions and with HDMI video signals from Blu-Ray or Scaling DVD player or Satellite receiver, that overscan is precisely zero. The format of the signal matches the fixed pixel display and it's mapped directly onto it.

There is the trivial case where a 720p signal is scaled before bing mapped onto a 1080p display, or a 1080i signal is both interlaced and scaled before being mapped onto a 720p display. But both of these are HD signals with 16:9 aspect ratios with zero overscan.

The visible artifacts from closed captioning and other embedded signals ARE visible in 480i analog images and in 480i digital subchannels multiplexed into the ATSC signal. For historical reasons, a lot of stuff was transmitted in the "blanking Interval", the black bar between 480i broadcast fields of old NTSC signals. Overscan WAS USED to eliminate such artifacts.

In modern ATSC televisions, most 4:3 subchannels are still displayed with overscan, to make the digital 480i signal suitable for broadcasting old 480i analog video sources, and to support such modern services as stock tickers and news tickers along the edge of the screen.

So take this new information and consider the messages above this one. Technically, everybody was entirely correct in what they said, but I don't believe that anybody understood that overscan is a SD subchannel feature only, and only because it was needed and is still needed in legacy 480i source material.
post #12 of 33
Quote:
Originally Posted by CatBus View Post

So you're saying modern sets max out at 2%? It's important I don't get this number too low, i.e. if there's a major manufacturer that defaults to 2.5% or 3%.

NO, I am saying the many current generation sets default to about 10% firmware overscan(to emulate an older CRT) plus about about 1-2% "physical" overscan to insure that the the edge of the image is under the Bezel. On almost all/if not all of these give you a "just scan" or equivalent display opton to eliminate the CRT emulation overscan leaving the 1-2% "physical" overscan in place. Some units also give you option to adjust the screen edge to just get under the bezel.
post #13 of 33
Thread Starter 
I swear I've seen overscan on 1080P/HDMI/Blu Ray out-of-the-box on a modern LCD, but it's been so long since I've seen an out-of-the-box system that I honestly forget what is normal.

After looking at things again, I think I can manage a margin of 27 pixels or so. It's not ideal, but I'd really rather play it safe. Unless someone thinks 27 is not enough... uggh.
post #14 of 33
You guys are dreaming, or remembering the "original" analog HDTVs, which were CRT RPTVs. Analog HDTVs did in fact incorporate overscan, for the same reasons as NTSC analog TVs. Digital HDTVs only incorporate overscan capability on subchannels.

Most HDTVs do in fact have two "zoom" settings. My Samsung calls them Zoom1 and Zoom2. They produce 25% stretch either horizontally AND Vertically (Zoom1) or Horizontally only (Zoom2). When an HDTV image in 16:9 is downrezzed and broadcast within a 480i ATSC subchannel, you can use Zoom1 to fill the 16:9 screen. Zoom2 I have never found a use for.
post #15 of 33
Thread Starter 
One of my "3% overscan" sources was here:

http://www.engadget.com/2010/05/27/h...all-tvs-do-it/

Maybe I am overthinking things. I'd sure like to just go right up to the edge.
post #16 of 33
Quote:
Originally Posted by CatBus View Post

I swear I've seen overscan on 1080P/HDMI/Blu Ray out-of-the-box on a modern LCD

Thats the way my new Samsung LCD HDTV works and also my Panasonic plasma HDTV.
On the Samsung the default "16:9" setting with a 1080i or 1080p source input will result in a 5% overscan (2.5% cropped on each edge) and I get zero overscan only by manually selecting the "Screen Fit" mode.
Similarly my Panasonic plasma HDTV has two selectable settings with a 1080i or 1080p source input: "Size 1" produces the 5% overscan and "Size 2" gives zero overscan.
With 480i/480p input sources, the sets always produce a 5% overscan, no zero overscan setting is supported there, though more crop/zoom modes are available as well.
post #17 of 33
OK, I'm going to venture a guess here. Some of you still own HDTV's from before the NTSC analog broadcasts were turned off. In other words, you have sets with BOTH ATSC digital and NTSC analog tuners built in. In the days when both ATSC and NTSC broadcasts were happening, these sets switched between digital and analog tuning modes automaticly as you scanned the airwaves.

If that's the case, since the only over-the-air broadcasts remaining are ATSC digital broadcasts, you have NO REASON WHATSOEVER to need the overscan feature, it is a legacy feature left over from now-obsolete NTSC tuners.

Digital broadcasts do not make use of a "blanking interval" between fields or frames to contain other data. With digital broadcasting, the pixel values, the sync timing, the audio, the closed captioning, and everything else are just seperate data sets, multiplexed together for broadcast. There is no data physically adjacent to video signals, and overscan is not needed to conceal the artifacts on the edge of the video frame - because there are no such artifacts.

The NEXT HDTV you buy doesn't need an overscan feature.
post #18 of 33
Threre are lots of low powered broadcasters with small coverage areas that were not required to transition to digital and therefore are still broadcasting in analog. Both analog and digital TVs can have overscan it is not restricted to sets with NTSC tuners since digital TV's also have to emualte the older CRT TVs.
AFAIK all US TVs also still have NTSC analog tuners for the use of many VCR's and video cameras which output on channel 3 or 4. Many manufacturers just don't list their NTSC tuner, they just list what digital tuners they have.
My 3 year old LCD TV has about 9% overscan and when I disable the overscan by selecting the "Just Scan" option I got artifacts from the blanking area which exists even on some 1080i and 720p digital channels untoll I adjusted the about 2% of overscan present to get the image under the bezel at the top of the screen.
With HDMI video the sound and the video are multiplexed over the same set of wires and contain a blanking area in order that they can be easily converted to NTSC for display on older analog only TVs.
post #19 of 33
Quote:
Originally Posted by Gary McCoy View Post

OK, I'm going to venture a guess here. Some of you still own HDTV's from before the NTSC analog broadcasts were turned off. In other words, you have sets with BOTH ATSC digital and NTSC analog tuners built in. In the days when both ATSC and NTSC broadcasts were happening, these sets switched between digital and analog tuning modes automaticly as you scanned the airwaves.

If that's the case, since the only over-the-air broadcasts remaining are ATSC digital broadcasts, you have NO REASON WHATSOEVER to need the overscan feature, it is a legacy feature left over from now-obsolete NTSC tuners.

Digital broadcasts do not make use of a "blanking interval" between fields or frames to contain other data. With digital broadcasting, the pixel values, the sync timing, the audio, the closed captioning, and everything else are just seperate data sets, multiplexed together for broadcast. There is no data physically adjacent to video signals, and overscan is not needed to conceal the artifacts on the edge of the video frame - because there are no such artifacts.

The NEXT HDTV you buy doesn't need an overscan feature.

My Samsung LCD is a current year 2011 model and all of their current models can select between overscan and no overscan on HD input sources but have fixed 5% overscan on 480i/480p sources independent of analog vs digital.
Analog NTSC is still used on many cable TV systems and also from older compositive video sources, even though OTA broadcasts are no longer analog. So even current TVs have to still support analog channels and video sources and provide overscan option.

Even on some digital SD channels I've seen the color noise at the extreme top of the frame, requiring the small overscan to eliminate...
post #20 of 33
Here is a quote from the link that follows the quot
"
United States: Most full-power analog transmitters were shut down on or by June 12, 2009, with the exception of "nightlight" analog stations (which broadcasted a video on how to set up a digital TV). These were shut down on June 26, 2009. As part of the June 2009 transition, all full power transmitters vacated channels 52 to 69. Low power transmitters that use channels 52 to 69 will be forced to vacate those channels by December 31, 2011. All analog low power transmitters will be forced shut down by September 1, 2015.
"

http://en.wikipedia.org/wiki/Digital...ion_transition
post #21 of 33
Thread Starter 
Crap. Outside Walford's 9% overscan (which sounds like what you'd see on a RPTV!), I'm hearing the number 5% a lot. I know I can accomodate 5%, even though it's not ideal. 9% is crazy. I don't know how I can work with that. Oh well...
post #22 of 33
Quote:
Originally Posted by CatBus View Post

Crap. Outside Walford's 9% overscan (which sounds like what you'd see on a RPTV!), I'm hearing the number 5% a lot. I know I can accomodate 5%, even though it's not ideal. 9% is crazy. I don't know how I can work with that. Oh well...

YMMV. When I owned a Sony VVEGA, I spent some time in the calibration routine tweaking the overscan to near zero. I ended up seeing the tips of a lot of dangling overhead microphones, that the TV studios never saw on their monitors due to the standard 5% overscan. It was distracting to enjoying the program, to be frank.
post #23 of 33
Quote:
Originally Posted by CatBus View Post

Crap. Outside Walford's 9% overscan (which sounds like what you'd see on a RPTV!), I'm hearing the number 5% a lot. I know I can accomodate 5%, even though it's not ideal. 9% is crazy. I don't know how I can work with that. Oh well...

My 9-10% is 4-5% on each edge. See the the following link:

http://en.wikipedia.org/wiki/Overscan
post #24 of 33
Thread Starter 
Quote:
Originally Posted by walford View Post

My 9-10% is 4-5% on each edge. See the the following link:

http://en.wikipedia.org/wiki/Overscan

Yeah I know the link

I was just hoping the "10% overscan" rule-of-thumb didn't apply to modern displays, and was kindof a rear-projection throwback...
post #25 of 33
It is not a rear projection throwback. There are still many older CRT based standard cabinet or rear projection models in use so almost all of the TV shows and movies still have no meaningfull content on the edges of their shows. Therfore overscan is still a good feature since it enlarges the size of the meaningfull content and text. Hoiwever, afaik at least one TV manufacturer calls overscan "Zoom1" and no overscan "full fit" or something like that.
post #26 of 33
Thread Starter 
Yes, but my question was whether *I* could place meaningful content in that area, if I knew that rear-projection units could safely be discounted. I'm still inclined to say that if I leave a 5% margin I'm safe in nearly all circumstances. It's the "nearly" that just kills me.
post #27 of 33
Don't forget all the Mitsubishi DLPs selling to average consumers, under $1k. I don't see how content makers can discount these.

(for those who don't know, these 2011 sets have 5% overscan (total, in either direction), and it can't be turned off.)
post #28 of 33
Thread Starter 
I've also read that broadcasters are accounting for 5% overscan in their HD signals (of course, I don't know if that's true...). Nevertheless, if it's good enough for broadcasters then it's good enough for me. i.e. people with >5% overscan would be used to having bits cut off.
post #29 of 33
I normallhy have overscan disabled on my LCD only because I often use it as a PC monitor and you always want 1:1 pixel mapping for PC applications for both clarity of small text and to insure you can see the Taskbar.
post #30 of 33
Quote:
Originally Posted by ndoggac View Post

From the 'overscan' wikipedia article:
On LCDs driven from a digital signal, no adjustment is necessary because all pixels are in fixed positions. Thus all modern computers can safely assume that every last pixel is visible to the viewer.

You could go up to as much as 1 or maybe 2% to be safe, as some manufacturers still induce some over-scan on digital displays. Although this is always much much less than old CRT's.

I wonder how much longer until sports broadcasts stop putting the scoreboard a 1/4 of the way into the screen?
Annoying!

A long time I read an article on ars tehnicha saying that they plan to keep the sports HUD for 5-8 years after the transition to digital. Was CBS, so don't expect it any time soon.
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