Strange Sky picture (ch 3 and 72)

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ArfurDaley

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Topic # 13460 11-May-2007 09:54

Over the past few weeks I have noticed when viewing TV3 or Nat Geo channel through the Sky digital decoder that the picture is shrunk to about 75% of it's normal size. It is centred on my 29" CRT (4:3 display). There are black bars on either side and above/below the picture (around 3 inches wide each). That's a lot of picture real estate to lose! The full image is there, just shrunk. I have confirmed that the decoder is set to output 4:3 Letterbox, as my first thought was that this setting had been changed somehow.

It only ever happens (to the best of my knowledge) on these 2 channels, but it isn't always like that.

Have Sky changed something in the way they broadcast TV3 and Nat Geo or is there a potential problem with my decoder?

ZollyMonsta

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Reply # 70333 11-May-2007 10:13

ArfurDaley: Over the past few weeks I have noticed when viewing TV3 or Nat Geo channel through the Sky digital decoder that the picture is shrunk to about 75% of it's normal size. It is centred on my 29" CRT (4:3 display). There are black bars on either side and above/below the picture (around 3 inches wide each). That's a lot of picture real estate to lose! The full image is there, just shrunk. I have confirmed that the decoder is set to output 4:3 Letterbox, as my first thought was that this setting had been changed somehow.

It only ever happens (to the best of my knowledge) on these 2 channels, but it isn't always like that.

Have Sky changed something in the way they broadcast TV3 and Nat Geo or is there a potential problem with my decoder?

Hi ArfurDaley.

TV3 and NatGeo on Sky are broadcast in 16:9 format now. Both channels are encoded directly in 16:9 (no widescreen flags to have the set top box switch between 4:3 and 4:3 letterbox).

What this means, on both channels, is anything they play that is in 4:3 format will be 'pillarboxed' (Black bars on the left and right of the screen). Add this to the 4:3 letterboxing (black bars top and bottom of the screen) and what you end up seeing on your 4:3 tv is the 'postage stamp' effect. The only way around this is to change your TV settings to stretch those pictures displayed in 4:3 on those channels (displaying as postage stamp)... or set your Sky set top box to 4:3 centrecut.

Centrecut will make the pictures full screen and avoid the postage stamp effect, however you will lose some picture information from the programmes in widescreen format on the left and right hand sides of the screen.

Its a trade-off between old and new technlogy. Both those broadcasters transmit like that and it is beyond any other broadcasters control, sadly.

Expect as the 4:3 content reaches the end of its play life, for the 4:3 content to slowly disappear from the channels. Until then though its a process of transition between the two.

Cheers,
ZollyMonsta

Check out my LPFM Radio Station at www.thecheese.co.nz

cyril7

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Reply # 70337 11-May-2007 10:15

Both TV3, and NatGeo are transmitting fulltime 16:9, hence your STB with the 4:3LB mode engaged will show top and bottom bars to enable the correct display of a 16:9 image on your 4:3 display. If they display any 4:3 material rather than ignorantly stretching it out across the 4:3 display they show it as it should be as a 4:3 image within a 16:9 frame. A consequence of this is that you get pillarbox bars eitherside in addtion to the LB bars top and bottom, end result is postage stamp.

Most of the time TV3 and Nat Geo show 16:9 material the only time you should see sidebars is when older 4:3 material is shown, check the TV3 news out and ensure that when the news readers are on the image is the whole screen width as the news presentation is in 16:9.

From what you describe everything is as it should be.

Cyril

ArfurDaley

9 posts

Wannabe Geek

Reply # 70342 11-May-2007 10:26

Thank you both for those very complete replies. I will just put up with the postage stamp picture for the meantime. Hopefully some time soon I can get myself a WS LCD anyway.

cyril7

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Reply # 70347 11-May-2007 10:48

TVOne and TV2 will be doing the same as from july31, expect more and more channels from Sky to do so as they upgrade there facilitites at Mt Wellington (due to complete latter this year).

Cyril