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LCD TV 720p 1080i confusion |
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#1 |
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Join Date: Mar 2004
Posts: 44
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LCD TV 720p 1080i confusion
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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#2 |
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Join Date: Apr 2007
Posts: 14,710
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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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#3 |
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Join Date: Mar 2004
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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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#4 |
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Join Date: Jul 2008
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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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#5 |
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Join Date: Aug 2008
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Quote:
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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#6 |
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Join Date: Mar 2006
Location: Scottish Borders
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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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#7 |
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Guest
Join Date: Apr 2007
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Quote:
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) 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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#8 |
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Join Date: Jun 2005
Location: Ramsgate Kent UK
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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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#9 |
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Join Date: Dec 2008
Location: London
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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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#10 |
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Join Date: Nov 2003
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Quote:
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.
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#11 |
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Join Date: Sep 2004
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Quote:
I read that the Progressive scan picture 720p would look better than the 1080i interlaced picture
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#12 |
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Join Date: Aug 2008
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Quote:
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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#13 |
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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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#14 |
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Join Date: Apr 2006
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Quote:
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.
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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#15 |
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1080i exists to save bandwidth and allow HD signals from cheaper source gear. That's why Sky uses it.
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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#16 |
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Quote:
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.
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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#17 |
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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 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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#18 |
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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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#19 |
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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. 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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#20 |
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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.
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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#21 |
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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
It was chosen as the most suitable, all things considered, and that probably still applies for the exact same reasons. |
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#22 |
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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 still for £260 incliding vat, I thought it was a good buy. |
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#23 |
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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. 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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#24 |
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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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#25 |
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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!! ![]() 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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