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why do some TV stations prefer interlaced?

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#1 Jimmy Jib

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Posted 03 April 2016 - 11:04 AM

Looking through my local ( Australian ) TV station's content delivery tech guidelines I read 1080i is preferred for HD and 576i for SD. I know some channels are broadcasting 720p, but it seems to me nobody is using 1080p yet? Why is this? I do realize this changes from country to country by the way...


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#2 Brian Drysdale

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Posted 03 April 2016 - 11:29 AM

It's because of bandwidth, interlace is a form of compression, The UK broadcasters use 1080i, as do most of the broadcasters around the world.


Edited by Brian Drysdale, 03 April 2016 - 11:29 AM.

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#3 Phil Connolly

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Posted 04 April 2016 - 01:02 PM

 For live TV and sport etc you don't want 25p as it would be too juddery and the bandwidth of 1080/50p would be too high - so 50i gives you enough motion detail for sport in the same(ish) bandwith of 25p. 25p content can easily be transmitted within 50i as 25psf - so it makes more sense to have 50i network as it covers you for both. 

 

You can't easily switch between 25p and 50i on traditional networks - so most standardise on 50i. Maybe film specific channels use progressive and IP based broadcasters such as Netflix can switch frame rates and use progressive. 

 

The 720p broadcasters tend to use 50fps or 60fps - they can do this as bandwith is lower then 1080


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