skyhd / 1:1 pixel mapping

[planetf1]

I have a samsung LCD/LEC tv UE46c6620. Connected to this is a new Amstrad Sky+ HD box (set to 1080i), and a Sony bluray BDP-S370

A couple of weeks ago we briefly connected a laptop over HDMI and immediately noticed part of the picture was chopped off. I quickly changed the screen image fit setting (from 16:9) to "screen fit" which appears to offer 1:1 pixel mapping on this set.

Since my other 2 primary sources are HD I assumed that it was appropriate to use this setting for all inputs, so that is what I'm using.

HOWEVER I've noticed that on some TV programs
- I occasionally see a green pattern (looks like data/noise) on extreme right/base of image - probably a pixel or two deep
- with "the gadget show" tonight
: the video used alternated (different shots) between filling the whole screen, and stopping about 0.5-1cm short in width
: the on screen graphics consistently filled the image, even when overlaying a chopped video
: the top 0.5cm or so was blank too

I can only assume these broadcasts are assumed to be watched using a safe area where those outlying pixels are lost -- surprising since this will involve some resampling and image degredation (I assume)

is this a sky phenomena?
Is this normal with all HD broadcast sources?
Do most ppl just run with default 16:9 settings except when viewing a more "pure" source - computer?
What about bluray?

Intrigued to understand more

nigel.

 

[Stevenage Neil]

Line blanking/Field blanking/Teletext?

I dunno really, but these things spring to mind.

 

[planetf1]

Yes my thought too, but didn't think that would apply in the digital HDTV space, assumed that was long behind us.

 

[Migman]

I always use 1:1 mapping, and just ignore the occasional oddity when it shows up

 

[planetf1]

inspected the various sky channels and it seems very variable
- sometimes picture seems just fine
- sometimes gap at top/bottom or sides
- sometimes edge of picture is unclean/noisy

Just looks like broadcast artifacts. Don't think there's anything wrong per-se, but this means even HD image is being resampled ...

 

[planetf1]

Ok other threads
- SKY News HD problem help - Sky+ HD - Digital Spy Forums - like the last comment on the thread
- itvhd - 1:1 pixcels is it really hd as getting a black bar on the right! ???? - Sky+ HD - Digital Spy Forums

Seems to confirm it's really a broadcast issue, and sometimes down to upscaling done by the broadcaster...

Seems a shame, if I have a 1080p screen I'd rather not have the picture "overscanned" and resampled!

 

[Migman]

Well, the broadcaster assumes (wrongly) that people are watching TV's that have been adjusted to 5% overscan, they won't see any of these artifacts, that was the way all tele's used to be, so i guess either they'll have to adapt there broadcasts or we'll just have to suck it up

 

[planetf1]

Yes @migman that seems to be the case. So fine, keep graphics in the safe area, but to assume overscan is right moving forward just seems so backward given the step change to HD..

 

[logiciel]

I have a samsung LCD/LEC tv UE46c6620.

Isn't this actually a LED TV?
On the question about what people do, my answer is leave the Sammy 46 3D LCD on the default setting and get perfect results from SKy HD at 1080i and BluRay at 1080p.

 

[planetf1]

It's labelled as an "LED" TV, yes. Of course from a technical perspective the panel is LCD, the change is the backlight being LED (edge in this model) rather than CCFL.

The "issue" is picture scaling - so there is no longer a 1:1 mapping between the incoming video stream and the display. You're right that to all intents and purposes ppl may regard this as "perfect" but as ever once you know more it can annoy!

 

[logiciel]

Yes, I guess it's a case of what you've never had you never miss.

 

[derek500]

HOWEVER I've noticed that on some TV programs
- I occasionally see a green pattern (looks like data/noise) on extreme right/base of image - probably a pixel or two deep
- with "the gadget show" tonight
: the video used alternated (different shots) between filling the whole screen, and stopping about 0.5-1cm short in width
: the on screen graphics consistently filled the image, even when overlaying a chopped video
: the top 0.5cm or so was blank too

I get the 'coloured' edges on some SD channels but not the HD simulcasts. Are you watching the simulcast of The Gadget Show on Five HD?

Some programmes, like Deal or No Deal on 4 HD have a half inch black bar at either side of the screen, but it's not obtrusive.

 

[muffins]

My advice would be 16:9 for sky, just scan for everything else.

 

[HDCriticalFan]

I've been using 1:1 pixel mapping for over a year. Here's what I've found :-

- ITVHD had a major "vertical black bar at the right hand side" for months.

- some channels (C4HD) used to have the occasional white "spot" in a corner (or two !).

- some upscaled SD material has a minor "jaggie" (usually just one step) along the top and/or bottom

- you do (quite rarely) see the picture not quite filling the screen on some camera shots in a programme


However, I've never seen the colour phenomena described here.

Oh, and it's probably not a good idea to use The Gadget Show as a control for picture quality

The other week they made the entire show using "consumer tech". To my amazement they managed to make the show look even worse than normal How do they do this

Waaaay back in 1998 I got a mini-DV camcorder. When playing back via s-video this looked quite noticeably better than Sky Digital. How come, over a decade later and using the very latest HD-capable kit, did they manage to make a show that looked sooo bad ?





Regards