HDTV Overscan/Underscan discussion

Caged · 5 Feb 2006 at 22:37

Overscan is something all TVs do, it's just the way it is. Nothing useful will ever be put into these safe boundaries, you are missing none of the film by having overscan.

Have a read of this, it seems obsessed about the subject, basically overscan is a leftover from CRT days where the signal was a bit dodgy at the edges, but you do sometimes get weird stuff happening at the edge of a picture, and overscan hides it.

http://www.mastersofcinema.org/reviews/03lookingbeyond.htm

Attu · 5 Feb 2006 at 22:59

When i used a DVE DVD on my Pioneer the over scan was well below the 5% markers, i cant actualy remember what the markers were 5% and 10% ? what ever they were it was well below the outer marker but would this be the same with all DVD's ?
Forgive me if youve already said but what DVD player are you using ? ...runs down stairs and puts Stealth on to find that scene

Attu · 5 Feb 2006 at 23:28

Hmmm mine is a bit between both of yours,

excuse the bad photo but it shows my screen shows more than yours on DVD but not as much when your using a PC, my DVD player is a Denon 1920 conected to a Pioneer 436 via HDMI in 720p, i switched between 480, 720 and 1080 and all showed thew same pic.
Ill try and connect my PC to my screen tomorrow if i get time and see if that makes and difference.

Andy

Mr Latte · 6 Feb 2006 at 00:19

Andy firstly thanks for going to the bother.
Interesting that when you changed the upscaling from 480p - 1080i the Pioneer made no difference. Can i ask if this was done via direct connection to the display or through the media box and did you compare it each way to the other? Not sure what res you run the PC in but youll definately need a custom res to get more image. Use the underscan tool within your GFX settings in the HDTV segment.

Id say your overscan showen is consistant with my 720p overscan.
Maybe the Pioneer just handles it better.

[SIZE=-2]MY Kit Sony SKDLV40A12U / Sony DAV-DZ 700 / Sony RDR-HX 710 / Sony Sky VTX-S760U / Alphason A03 Piano Black [/SIZE]

Caged, i can live with a little overscan but i think ive showed an example that this is a tad much. I know were not talking Pan/Scan here but i want what the director intended not 8% or whatever of it missing if i can help it. By the way your link shows exactly the advantages yet you seem to think "oh nothing important is missing" * Cue Queen "I Want It All"

What may be interesting is if others compare with their sets with any material and if its possible to help them discover that perhaps a HTPC with custom res may have an advantage.

Logan09 · 6 Feb 2006 at 00:57

This seems to be a problem with a number of HDTV sets. I have a Samsung SP50 and I get overscan from my HTPC when set to 50Hz, but much less when set to 60Hz!?!

There's a huge thread about the overscan on the SP50 over at AVforums (here) which gives some insight into why the overscan exists (seems to be something to do with the sets being designed initially for 60Hz and then not scaling properly at 50Hz). It's worth a read.

Caged · 6 Feb 2006 at 01:01

Mr Latte said:
Caged, i can live with a little overscan but i think ive showed an example that this is a tad much. I know were not talking Pan/Scan here but i want what the director intended not 8% or whatever of it missing if i can help it. By the way your link shows exactly the advantages yet you seem to think "oh nothing important is missing" * Cue Queen "I Want It All"

That link mentioned directors saying stuff like "the author of the commentary mentions Godard's habit of adding little unexplained elements, like the lamp at Prokosch's villa turning itself off and on", and by eliminating overscan you can see the lamp being turned on and off. This means that the overscanned picture was what the director intended you to see. If you consider seeing either a mix of what the director didn't intend you to see, or something that doesn't matter an advantage, then be my guest.

Did the overscan bother you before you compared it?

Logan09 · 6 Feb 2006 at 02:30

The problem is that if you're using a HTPC then your comp does all the resizing to whatever your screen resolution is set to (e.g. 1280x720). If the display then scales again so the 1280x720 image is overscanned on your 1280x720 display then you are not getting a true 1:1 image and as such not only will you miss certain information, but the image will not be as good as it could be.

Having said that, bizzarely I can only achieve a true 1:1 pixel mapping on my Samsung SP50 by overscanning the image, which seems odd that if a 1280x720 picture cannot be displayed without overscan onto at 1:1 then the display must actually be somewhat less than 1280x720. You could argue that this means I do not have a true 720p display.

ripkord · 6 Feb 2006 at 03:43

I think youre worrying too much about it mate, you probably wouldnt have noticed if you werent messing around with the resolutions anyway. Hope you find something that puts your mind at ease though, if not, its only a matter of time....... you'll forget about it and start to enjoy your HDTV again

Mr Latte · 6 Feb 2006 at 12:42

Overscan has always annoyed me, my last CRT "Panasonic 36PD30" was even tweaked via the service menu.

I agree to an extent its not that big of an issue but with so much being aparent here i think its worth others checking if their a little bothered. Theirs no need for such an excessive amount as whats happening on mine, maybe the bravia is an exception.

Ive already showed the solution with custom PC res that underscans so that none of the image is missing. Having 1:1 HDTV or the display scale to its native from the custom PC res doesnt matter in this respect you still get the benifit of the tweaked "underscan" image, thats the whole point of underscan.

1:1 would be nice yes but is overrated for movies.
Go into any electrical dealer and look at a HDTV display and tell me which are 1:1 and those that arnt, imo its really only more aparent with text.

37" Plasmas 1024x768 res 50" Plasmas 1366x768 Majority of LCDs 1366x768 some LCDs 1280x720m all HDTV but can you look and tell whats what?

davetherave2 · 6 Feb 2006 at 13:55

The overscan issue on my new Sony TV caused me no end of headaches. I must have spent a good few hours researching and trying to resolve the issue.

Eventually I stumbled on a solution by luck rather than by design of using a resolution of 1232*692 this allows me to see the whole of the desktop/movies from my htpc.

This seems to have stopped all the overscanning issues that I have had and picked up those extra bits of details that have been missing at the edge of the screen on my movies.

As I am still fairly new to all things audio/visual I am picking things up as I go along but I have to say that some of you are extremely knowledgable about this subject and have opened my eyes to a whole area of home entertainment that I have been ignoring for several years.

Thank you all.

Mr Latte · 6 Feb 2006 at 19:17

Look forward to more tests...

QUESTIONS:
davetherave2 what Sony do you have?
attu is yours 43" or 50"?

This stuck in my head today so heres some thoughts:

Take 1280x720 thats a 720p source displayed on a 1366x768 panel which the majority of Panels are.

Lets Count:
So 720p thats 921600 Pixels that has to be filled into a 1049088 pixel area
The difference then is 127488 pixels
Taking this difference we work out the scaling required.
As a percentage of the original source this requires approx 13.5 scaled increase to fill a 1366x768 panel

Keep that thought:
Hold on that seems quite a lot requiring an approx 13.5 increase in size to fit?
Now personally id of thought "overscan" on flat display technology would have been minimal which perhaps isnt the case.

Lets take an estimated guess and say an average HDTV with 720p material
overscans 5% left/right and 3%top/bottom. Ok so thats a combined 8%

If then approx 13.5% was the scaled value required to fill the 1366x768 panel less the 8% hidden in overscan then really only approx 5% scaling is actually seen by the viewer, is this why overscan is applied so scaling doesnt look overscaled and picture quality is maintained?

Quick summary:
720p source scaled to a 1366x768 panel is approx 13.5% increase
Average HDTV (may have) 8% overall overscan
Therefore the viewed scaled area is only approx 5.5% scaled from the original 720p source

Sorry if this is going a bit far but needed to get it off my chest.
However it seems overscan & scaling go hand in hand. Its obvious a DVD requires a lot more scaling with its 720x480 to fit a 1366x768 panel and the reason why so much was lost in the overscan process.

Of course different brands and models will use different scalers and scaling techniques but none the less Sonys DVD scaling is a bit dissapointing with loosing so much on this particular model, or really is it more common than some may think?

mcmad · 6 Feb 2006 at 20:04

Mr Latte said:
Of course different brands and models will use different scalers and scaling techniques but none the less Sonys DVD scaling is a bit dissapointing with loosing so much on this particular model, or really is it more common than some may think?

its very common mate, dissapointingly so, I posted in another thread about interlacing/scaling on current tv's, pretty much all of them are bloomin awful. The panels are normally decent, but they cut costs hugely on the processing side of things.

A good friend of mine splashed out 3 grand on a 1080p Philips set thinking this would be the perfect match for his HD HTPC, we spend bloomin ages trying to get it set up correctly & we just couldn't get it right, it looked ok but comparing it to a dell widescreen PC monitor the picture was always fuzzy looking.. eventually found a statement from philips about it, basically it aint a 1080p set, it has a 1080p panel but it cant process 1080p & they did it to cut costs, this is on a 3 grand tv so you can imagine what standard of video processing is used on cheaper sets..

He got a refund & we tried a few other sets, none of them matched the PC monitor PQ, again they aint bad pictures, but they could have been so much better with decent processing hardware.

Mr Latte · 6 Feb 2006 at 20:49

True HTPCs on HDTVs is a very large MINEFIELD.

Another problem is many models use VGA with 1:1. However id like to see these owners try HD-DVD or BLU-RAY come Vista etc. VGA is not compatible with HDCP so anyone expecting to adopt HiDef Disc formats into their HTPCs are gonna be mightly dissapointed.

Id rather have my HDMI connection with "my own overscan preferance" settling for its minor scaling to native anyday. My custom res still give me more video information with 720p and 1080i movies so overall you gain with every video source over an internal HDTV scaler, if overscan does indeed bother the person.

The Sony is one of the better recent models for HTPC although the Pioneer/Panasonic Plasmas are popular too, now i wonder how they all compare with DVD overscan, mmmm

Shimmyhill · 6 Feb 2006 at 20:56

HDCP is irrelevant, it is almost as useful as macrovision.

The issue here is that DVI + HDMI where rushed out and do not have the flexability of VGA. Look at all the HDMI revisions and they are gradually adding missing res/refresh combo's.

I think that by the time its all settled we will all be on new screens and have another issue to deal with (HD-DD anyone

)

Mr Latte · 6 Feb 2006 at 21:07

Shimmyhill said:
HDCP is irrelevant, it is almost as useful as macrovision.

The issue here is that DVI + HDMI where rushed out and do not have the flexability of VGA. Look at all the HDMI revisions and they are gradually adding missing res/refresh combo's.

Sorry youll have to re-explain what you mean.
In your opnion whats so good with VGA, heres some pointers you can answer back on.

ADV
1:1 Pixel Mapping is possible but not even always available depending on model
Every PC has one

DISADVANTAGES
Not as sharp requires a digital-analouge conversion
VGA isnt HDCP compatible nor upgradeable with upcoming DRM protected Hi-def material
PCs are converging with consumer products using HDMI connections
Windows Viista with the latest version of MCE will require HDCP compatibility. This includes 95% of TFTs they arnt HDCP compatible even though they are DVI based.

HDCP
This is fully adaptable, say a company launches a macrovision style bug blaster for HDCP. You may think you have the protection beat, but all they do is then program the digital keys that this device uses and the list of disallowed/illegal keys will be ever growing and they can be pumped down through your internet or put on each individual disc. It will then cut the digital handshake between your display as it detects the illegal keys for the now rouge device.

Who knows for sure but this is what ive read, (Engadget?) i doubt the protection will easily be beaten when its upgradable this way.

davetherave2 · 6 Feb 2006 at 22:42

Mr Latte said:
Look forward to more tests...

QUESTIONS:
davetherave2 what Sony do you have?
attu is yours 43" or 50"?

I have the 50" model as per my sig. Can't wait untill I get my hands on a beta copy of vista MCE and get hold of a hd dvd drive and then I can truely test out my tv as it was meant to be used.

Have tried some of the wmv hd stuff and there seems to be varying degrees of quality. Tried a copy of T2 EE and some elements look so clear and sharp when other parts of the film look fairly ordinary and grainy. Maybe that is because I haven't tweeked my htpc yet but I'm sure I will get round to it.

Just need an xbox360 to put it through its paces.

Mr Latte · 7 Feb 2006 at 00:33

Can i ask if youve tried or compared VGA to DVI-HDMI via PC connection.

You mentioned

"Eventually I stumbled on a solution by luck rather than by design of using a resolution of 1232*692 this allows me to see the whole of the desktop/movies from my htpc. "

My friend has onboard intel GFX (no HDTV modes) though i wasnt sure if the model only accepted 1024x768 as it mentioned this within the manual. Please just to confirm then that with this Sony model you have and that HDMI is best with possibly the only way of getting larger than 1024 resolution via PC?
He should be chuffed when i tell him...

On a further note have you tried a custom 1920x1080 desktop with "interlaced"

davetherave2 · 7 Feb 2006 at 01:55

I have used the vga connection only for gaming and it seems to be ok wish it could do 1280X1024 as I normally have on my 17" TFT panels but you can't have everything.

Yes hdmi is the way to go if your looking for a bigger desktop but as I said text looks a little blurry but not noticable in MCE given that it is designed to work on a standard tv res.

As for when I try to use a 1080i setting within my htpc the screen just seems to blank out so will have to investigate this further.

I'm wondering if the 1080i option only works with an upscaling dvd player or my 9800AIW is just not good enough to do it.

Either way I will investigate and try and get some answers for you.

I will have a go with my main games machine and see what happens.

Mr Latte · 7 Feb 2006 at 02:59

Ok thanks, cant talk with regards ATI but on Nvidia there is a interlaced box to tick for interlaced resolutions. You MUST set interlaced hench 1080i, see how you get on.

BoomAM · 7 Feb 2006 at 03:18

Samsung 26" HDTV:

I cant say ive noticed it with DVDs, or on my GC.
But i recently found that a significant portion of my Xbox's output was overscanned on all of the edges of the screen. So i changed some settings in XBMC to fix that. Im unsure if it was a Xbox or TV problem though. That was at 1080i.
Although im swaying towards a TV problem, as some resolutions are 'too big' for the telly and cause it to 'scroll' with the mouse. But, that was with OSX, so it could be OSX, as im using some modded 'drivers' to enable dual outputs.