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Old 15-04-2009, 09:17
bootgaz
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I currently have a Technika 37 1080 tv that i bought in January. It has recently started playing up and will be taking it back to get a refund. I have it hooked up to a Sky HD box and dvd player. My viewing distance is around 2 metres away.

Firstly when i look at the picture settings though the HDMI connection it says the picture is 1080i, is that down to my tv being 1080i or is it down to sky broadcasting in 1080i. I am not sure if my tv is full 1080p.

If it is only 1080i would i see any difference on the HD content if i was to get a 720p tv instead.

Please help so confused.
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Old 15-04-2009, 09:32
Moony
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720p is lower resolution than 1080i - so you would in all probability notice a loss of detail by going to a 720p TV.
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Old 15-04-2009, 09:38
bootgaz
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I read that the Progressive scan picture 720p would look better than the 1080i interlaced picture plus with only a 37 inch tv you wouldnt notice the difference. This is the table i found and are grouped in order of quality.

480i (standard definition, 480 lines interlaced)
480p (standard definition, 480 lines progressive)
1080i (high definition, 1080 lines interlaced, effectively 540 lines)
720p (high definition, 720 lines progressive)
1080p (high definition, 1080 lines progressive)
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Old 15-04-2009, 10:15
Willie Wontie
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The trouble with a 720p TV as opposed to a 1080i TV (if you can find such a thing) is that Sky HD, by default, broadcasts all its high definition output at 1080i, so to display it correctly on a 720p TV the picture would first need to be deinterlaced, which obviously takes time and involves scaling. You can set the Sky HD box to output at 720p, but then the Sky box is doing the deinterlacing before outputting the 720p signal. At 1080i output to a 1080i TV, no deinterlacing and rescaling is required at either Sky box or TV end.

A 1080i TV is pretty much the standard for HD Ready - and is certainly the most natural for Sky HD (and any other UK broadcast high definition television).
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Old 15-04-2009, 10:35
Scrolllock
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I read that the Progressive scan picture 720p would look better than the 1080i interlaced picture plus with only a 37 inch tv you wouldnt notice the difference. This is the table i found and are grouped in order of quality.

480i (standard definition, 480 lines interlaced)
480p (standard definition, 480 lines progressive)
1080i (high definition, 1080 lines interlaced, effectively 540 lines)
720p (high definition, 720 lines progressive)
1080p (high definition, 1080 lines progressive)
1080i only looks softer with very fast moving video.
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Old 15-04-2009, 14:20
emptybox
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I believe your Technika TV is Full HD 1080P, which means it has a resolution of 1920 x 1080, which is ideal for HD material transmitted at 1080i (Sky HD etc).

The idea was that transmitting at 720P might be better for fast moving sports etc, but as yet nobody transmits HD at this in the UK afaik.
Transmitting at 1080P would be best of all, but would take too much bandwidth at present.

At this cheaper end of the market, you might find that a TV with a lower resolution, say 1366 x 768, might display standard def pictures better that a 1080 line one, but if you mostly watch through your SkyHD box, then that won't really be a consideration, as everything will be upscaled by the box anyway (with the box set to 1080i).
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Old 15-04-2009, 16:39
Moony
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I read that the Progressive scan picture 720p would look better than the 1080i interlaced picture plus with only a 37 inch tv you wouldnt notice the difference. This is the table i found and are grouped in order of quality.

480i (standard definition, 480 lines interlaced)
480p (standard definition, 480 lines progressive)
1080i (high definition, 1080 lines interlaced, effectively 540 lines)
720p (high definition, 720 lines progressive)
1080p (high definition, 1080 lines progressive)
This is fundamentally incorrect. The 1080i picture has 1080 lines of information - exactly the same as 1080p.

Most movies are shot at 24fps (call it 25 for simplicity sake). Therefore on a 50hz TV you have two options - interlace or progressive scan.

For a TV running in interlace mode - the picture on the screen is refreshed every 50th of a second, however only half of the image is shown per refresh (i.e. lines 1,3,5... then lines 2,4,6...).

For a TV running in progressive scan mode - the picture is still refreshed every 50th of a second, but to match the framerate of the movie - each frame of the movie has to be displayed twice in quick sucession so you get lines 1,2,3,4,5,6.... then 1,2,3,4,5,6....

The important fact however is that every 25th of a second the entire movie frame is effectively displayed at its full resolution (i.e. you get lines 1,2,3,4,5,6 etc displayed every 25th of a second regardless of whether you are watching 1080i or 1080p).
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Old 15-04-2009, 16:58
bishy
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Hi Moony, Now you've managed to confuse me.....how is a lcd or plasma tv supposed to show odd lines etc. It was my supposition that lcd and plasma tv's showed the whole screen at once, not in lines, as it has no electron scanning beams.

I think I need Nigel to help me out with this.....Come on Nigel close that highly profitable shop and come and explain this for me in layman terms.

Thanks in advance.

bishy.
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Old 15-04-2009, 17:03
RED_
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Haven't read the thread but from what i know, 1080i is the same as 720p. Due to all the progressive and interlaced stuff. Hope that helps in someway.
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Old 15-04-2009, 17:10
meltcity
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when i look at the picture settings though the HDMI connection it says the picture is 1080i, is that down to my tv being 1080i or is it down to sky broadcasting in 1080i. I am not sure if my tv is full 1080p.
The picture says 1080i because that is what Sky broadcasts.
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Old 15-04-2009, 18:02
_ben
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I read that the Progressive scan picture 720p would look better than the 1080i interlaced picture
Its true that a program generally looks better if its produced using progressive rather than interlaced (that's what the BBC says in its official HD guidelines for producers) and it would look better if broadcast in progressive rather than interlaced (but nobody in the UK does this currently). Given that what your box receives is 1080i, you'd be better feeding it to your TV as 1080i and letting the TV do what it needs to do regarding deinterlacing and scaling to its native resolution. The only exception to this would be if your TV had a really crappy deinterlacer but your box had a really good one, then it would be worth letting the box do the deinterlacing and scaling and just tolerate the additional scaling that the TV will need to do to match its native resolution.
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Old 15-04-2009, 18:54
Scrolllock
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Its true that a program generally looks better if its produced using progressive rather than interlaced (that's what the BBC says in its official HD guidelines for producers) and it would look better if broadcast in progressive rather than interlaced (but nobody in the UK does this currently). Given that what your box receives is 1080i, you'd be better feeding it to your TV as 1080i and letting the TV do what it needs to do regarding deinterlacing and scaling to its native resolution. The only exception to this would be if your TV had a really crappy deinterlacer but your box had a really good one, then it would be worth letting the box do the deinterlacing and scaling and just tolerate the additional scaling that the TV will need to do to match its native resolution.
As I live in America, the only place in the world that I know of that broadcasts 720P, I can easily tell you that 1080i looks very obviously superior to 720P in most cases, with the exception of very fast motion. Even there it doesn't make as much of a difference as one might think. Until 1080P replaces 1080i as a transmission source 1080i will be, for all practical and visual purposes, the superior format compared to 720P.
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Old 15-04-2009, 20:17
Chris Frost
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1080i exists to save bandwidth and allow HD signals from cheaper source gear. That's why Sky uses it.

The 720p signal from a Sky box would be good for sports and other fast motion, but a HD box costs about $30 to make and they use a $3 chip for the conversion from 1080i to 720p. Hence it's rubbish.

1080i is 1920x540 for the odd line field, followed by 1920x540 for the even field. A 1080p TV will recompose (deinterlace) the image to make a 1080p picture. Quite how a lower resolution TV will handle 1080i depends on the video processing. If the TV can handle a 1080p input then it should really do the same trick as a full 1080p res TV, but just scale the image down to the lower display resolution.

Regards

Chris Frost
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Old 15-04-2009, 20:49
Nigel Goodwin
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Hi Moony, Now you've managed to confuse me.....how is a lcd or plasma tv supposed to show odd lines etc. It was my supposition that lcd and plasma tv's showed the whole screen at once, not in lines, as it has no electron scanning beams.
Yes, it shows the entire screen at once, no scanning lines, and it's neither progressive nor interlaced - that's the signal source, NOT the display.

Also a 1080i picture is 1080 lines resolution, exactly the same as a 1080P picture - there's a lot of misinformation about 1080i.

1080i provides 25 x 1080 resolution pictures per second. 1080P25 provides exactly the same, but 1080P50 (the one that takes too much bandwidth to broadcast) provides 50 x 1080 resolution pictures per second. So more pictures per second for 1080P50, rather like a 100Hz set - except a 100Hz set only makes up the extra 25 frames per second.
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Old 15-04-2009, 20:54
Nigel Goodwin
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1080i exists to save bandwidth and allow HD signals from cheaper source gear. That's why Sky uses it.
You mean it's not because it was decided that all EU HD broadcasting was going to use 1080i at a meeting of the EBU - because it was - which sounds a far more likely explanation.

Notice that the BBC use it, the ITV use it (on the odd occasion they use any at all), as does everyone else. The same EBU meeting agreed that equipment should be able to receive both 1080i and 720P, to give the scope for change in the future if they decided to use 720P later.

1080P wasn't required to be part of the spec at all, so doesn't sound likely in any reasonable time frame, if at all.
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Old 15-04-2009, 20:58
meltcity
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1080i provides 25 x 1080 resolution pictures per second. 1080P25 provides exactly the same, but 1080P50 (the one that takes too much bandwidth to broadcast) provides 50 x 1080 resolution pictures per second. So more pictures per second for 1080P50, rather like a 100Hz set - except a 100Hz set only makes up the extra 25 frames per second.
Not quite.

1080i provides 25 x 1080 line resolution pictures per second, but only where the source is progressive, such as on feature films or high end TV dramas and documentaries.

For normal video material 50 pictures are recorded per second. The perceived resolution depends on the amount of motion in the between the pictures. On a static image the resolution will be 1080 lines. On a moving image the resolution will be somewhere between 540 and 1080 lines.
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Old 15-04-2009, 21:04
Nigel Goodwin
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Not quite.

1080i provides 25 x 1080 line resolution pictures per second, but only where the source is progressive, such as on feature films or high end TV dramas and documentaries.

For normal video material 50 pictures are recorded per second. The perceived resolution depends on the amount of motion in the between the pictures. On a static image the resolution will be 1080 lines. On a moving image the resolution will be somewhere between 540 and 1080 lines.
So how would such a video source of 50 fields (better term than 'pictures' as they aren't full pictures) benefit from a progressive broadcast system? - it obviously wouldn't - because the source is already interlaced.

So any progressive sourced material will benefit equally 1080i and 1080P - with the exception of 1080P50, where you get double the frame rate (assuming a 1080P50 source).
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Old 15-04-2009, 21:56
bishy
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@ Nigel, Thanks for your concise explanations everything is much clearer now.

One last question.....Is it at all likely that eventually some or indeed all broadcasters will transmit in 1080p? Surely if they did, a lot of the current confusion would disappear.

Once again thanks for all your help.

bishy.
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Old 15-04-2009, 22:50
Chris Frost
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You mean it's not because it was decided that all EU HD broadcasting was going to use 1080i at a meeting of the EBU - because it was - which sounds a far more likely explanation.

Notice that the BBC use it, the ITV use it (on the odd occasion they use any at all), as does everyone else. The same EBU meeting agreed that equipment should be able to receive both 1080i and 720P, to give the scope for change in the future if they decided to use 720P later.

1080P wasn't required to be part of the spec at all, so doesn't sound likely in any reasonable time frame, if at all.
Nigel, so what if the EBU finally decided on 1080i. You think they made that decision on the basis of quality; or cost. Hmmm....I wonder which it could have been?...ooh it's a toughie

All the politicking and spin doesn't change the fact that of the three possible broadcastable HD signal formats 1080p needs the most bandwidth, followed by 720p, and then 1080i brings up the rear. And it's a fact that dealing with lower bandwidth signals means lower costs for the broadcast equipment manufacturers and TV companies.. And it's also a fact that 1080i allows the broadcasters more channels for the same amount of broadcast bandwidth; which leads to greater potential advertising revenue. And finally of course there's the whole 1080p TV thing which oh so conveniently allow TV manufacturers to spin out a new generation of TV technology for the public to buy it to. Oh, quell surprise!!

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Old 15-04-2009, 22:52
Nigel Goodwin
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One last question.....Is it at all likely that eventually some or indeed all broadcasters will transmit in 1080p? Surely if they did, a lot of the current confusion would disappear.
I would have said it's highly unlikely, and really pretty pointless - the difference from 1080i to 1080P is really pretty small, and only on very fast moving action. Bear in mind there are pretty well no sets or set-top boxes that could receive it anyway, so new boxes would be needed.

There's not really much confusion, apart from on here

For the majority of the public, HD is HD - that's all that matters - they aren't confused about it.
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Old 15-04-2009, 22:55
Nigel Goodwin
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Nigel, so what if the EBU finally decided on 1080i. You think they made that decision on the basis of quality; or cost. Hmmm....I wonder which it could have been?...ooh it's a toughie
But your original point was that Sky choose 1080i to save costs, Sky didn't choose it - the EBU did - and Sky were only one of the many members involved.

It was chosen as the most suitable, all things considered, and that probably still applies for the exact same reasons.
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Old 16-04-2009, 00:49
stuntmaster
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1080i exists to save bandwidth and allow HD signals from cheaper source gear. That's why Sky uses it.

The 720p signal from a Sky box would be good for sports and other fast motion, but a HD box costs about $30 to make and they use a $3 chip for the conversion from 1080i to 720p. Hence it's rubbish.

1080i is 1920x540 for the odd line field, followed by 1920x540 for the even field. A 1080p TV will recompose (deinterlace) the image to make a 1080p picture. Quite how a lower resolution TV will handle 1080i depends on the video processing. If the TV can handle a 1080p input then it should really do the same trick as a full 1080p res TV, but just scale the image down to the lower display resolution.

Regards

Chris Frost
Aha! thats what my Akura APL3221W - HDID must be doing then, it's res is: 1366x768, but it does accept a 1080p signal. I know because my PS3 detected it and the TV's osd info panel showed it was in 1080p, and does accept the 24hz mode from blu-ray movies. also tested, Die-Hard 4.0 played fine. and info panel showed it was in 24hz mode.

still for £260 incliding vat, I thought it was a good buy.
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Old 16-04-2009, 03:20
Chris Frost
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But your original point was that Sky choose 1080i to save costs, Sky didn't choose it - the EBU did - and Sky were only one of the many members involved.

It was chosen as the most suitable, all things considered, and that probably still applies for the exact same reasons.
Firstly I think you're possibly looking too deeply in to the comments and phrasing on the forum.

Second, you and I both know that Murdoch's henchmen will have been lobbying like crazy behind the scenes to get 1080i accepted as the de facto broadcast standard. The financial implications of any other decision would have been a disaster. And why did they want 1080i - to save money and boost profits.

It keeps coming back to the same financial argument.
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Old 16-04-2009, 05:16
timbo995
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From the little I know of HD, 720P is only better than 1080i if you are dealing with an image from a compressed source eg Blu-ray, H264 file etc..
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Old 16-04-2009, 07:18
tedjrr
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Nigel, so what if the EBU finally decided on 1080i. You think they made that decision on the basis of quality; or cost. Hmmm....I wonder which it could have been?...ooh it's a toughie

All the politicking and spin doesn't change the fact that of the three possible broadcastable HD signal formats 1080p needs the most bandwidth, followed by 720p, and then 1080i brings up the rear. And it's a fact that dealing with lower bandwidth signals means lower costs for the broadcast equipment manufacturers and TV companies.. And it's also a fact that 1080i allows the broadcasters more channels for the same amount of broadcast bandwidth; which leads to greater potential advertising revenue. And finally of course there's the whole 1080p TV thing which oh so conveniently allow TV manufacturers to spin out a new generation of TV technology for the public to buy it to. Oh, quell surprise!!

Various EBU members (and others) conducted tests in an attempt to determine a common position. Clearly informed by North American experience the opening perception was that both 720p and 1080i should be supported, and used equally. The reason for this was that 1080i (60 fields/s) appeared to be a good compromise when dealing with conventional video and adapted well to showing 24fps feature films using drop-frame, even in defiance of a default 24p mode. 720p very defiantly gave a much better performance for sports, giving better perceptive detail in close motion shots than 1080i.

However, this was Europe and different conditions apply due to the domestic frame rate.

It would appear that whilst 720p was tantalising, 50Hz perception tests revealed that it had a tendency to induce a sense of mild nausea in the audience, especially during high-motion content elements. Had this not been the case one suspects that Spy Sport would have adopted 720p. So, for a given data rate 720p gives much better detail in sport than 1080i; but it makes you sick at 50Hz, but not at 60Hz?

1080i performed better in perception tests almost matching 1080p, infact when 1080p was tested along-side 1080i in a fixed rate test, 1080p was dreadful. There was a huge debate amongst engineers over whether interlace had a role in modern digital systems, the trouble was that 1080i was a good compromise, and performed well in its effective 1080p@25Hz when showing feature films.

1080p is a viable system, BluRay disks support it, albeit usually at 24Hz; broadcast systems are currently challenged by it though. Video at 50Hz 1080p either has to have too high a data-rate, or require too much intensive blunt-end processing to cope with a GOP long enough to put extra B frames where all the odd fields would have been.
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