Hi,
everyone is offering HDTV screens/receivers, but most have only 768 lines.
The old UHF (UK) standard terrestial tv were based on 625 line transmission.
Will 768 line give much improvement?
Why are the retailers offering so few screens/monitors that meet the 1080 line standard? and the few that do at such inflated cost.
What's the story?
everyone is offering HDTV screens/receivers, but most have only 768 lines.
The old UHF (UK) standard terrestial tv were based on 625 line transmission.
Will 768 line give much improvement?
Why are the retailers offering so few screens/monitors that meet the 1080 line standard? and the few that do at such inflated cost.
What's the story?
Welcome to America a couple of years ago. After 2009 when the mandated switch to HD comes, prices the world over will likely plummet and the higher resolution will become more common where it is the local standard.
The UK standard of 625 lines was based on an interlaced picture at 50Hz no less.
The HDTV sets you're speaking of are 780p (progressive not interlaced) a small increase in line count but a large increase in information content. Since the entire screen, not just half is updated 50/60 times per second the information content is about double.
HDTV also has 1920 (maximum) horizontal pixels, I think that calculates to a maximum bandwidth of 88MHz whereas the British PAL standard was limited to 4.25MHz bandwidth.
So the total amount of maximum available information (video detail) has increased by about 40 times. I keep using the word maximum because the HDTV standards do not require providers to use all the available bandwidth, but even if only half is used the eye is presented with roughly 10 times the information.
The TV has to scan at least twice as fast to keep up with the information flow and almost 3 times for 1080p, cost was a problem with CRTs, now with microdisplays, scan rate and information rate can be different if the designer so chooses.
The HDTV sets you're speaking of are 780p (progressive not interlaced) a small increase in line count but a large increase in information content. Since the entire screen, not just half is updated 50/60 times per second the information content is about double.
HDTV also has 1920 (maximum) horizontal pixels, I think that calculates to a maximum bandwidth of 88MHz whereas the British PAL standard was limited to 4.25MHz bandwidth.
So the total amount of maximum available information (video detail) has increased by about 40 times. I keep using the word maximum because the HDTV standards do not require providers to use all the available bandwidth, but even if only half is used the eye is presented with roughly 10 times the information.
The TV has to scan at least twice as fast to keep up with the information flow and almost 3 times for 1080p, cost was a problem with CRTs, now with microdisplays, scan rate and information rate can be different if the designer so chooses.
Why not ask your local dealer for a demonstration?
Even at 768, the improvement is impressive; at 1080, it's breathtaking!
Even at 768, the improvement is impressive; at 1080, it's breathtaking!
Hi,
I'm still a bit lost here. So I might be reaching incorrect conclusions.
A progressive display at 100Hz contains the same detail as an interlaced screen that inserts the alternate line information on the first half and then fills in the other lines in the other half and the whole screen is refreshed at an effective 50Hz. but each half picture is displayed at an effective 100Hz. Thus avoiding flicker.
From terrestial transmission or a doctored DVD that is intended to SELL the advantages of HDTV?
Would the comparison be legitimate?
Would the demonstrator know if the signal was 768 or 1080 lines?
I note the use of 780p in a response but the HDTVs are being sold as 768. Are they compatible?
I'm still a bit lost here. So I might be reaching incorrect conclusions.
the difference between progressive and interlaced is not about information content. It is about preventing apparent flicker.
A progressive display at 100Hz contains the same detail as an interlaced screen that inserts the alternate line information on the first half and then fills in the other lines in the other half and the whole screen is refreshed at an effective 50Hz. but each half picture is displayed at an effective 100Hz. Thus avoiding flicker.
I am asking about vertical resolution. I accept that 4/3 format contains less hroizontal information than 16/9 format.
where does the demonstrator obtain the 625 line display?
From terrestial transmission or a doctored DVD that is intended to SELL the advantages of HDTV?
Would the comparison be legitimate?
Would the demonstrator know if the signal was 768 or 1080 lines?
I note the use of 780p in a response but the HDTVs are being sold as 768. Are they compatible?
Most are using DVD; a few are now showing Sky.
I think so. Of course, the material is designed to 'show off' the system, which is fair enough. Ask to see it in LD too for comparison.
I'd hope so😱 If not, go somewhere else!
UK transmissions use 720 lines, so either of those will be capable of displaying the picture.
so we are buying lower grade HDTV to display 720 lines rather than transmitting/receiving 625 lines.
Please help me overcome my (somewhat biassed) prejudice.
Expensive technology for the sake of lining the pockets of the manufacturers/retailers. Convince me.
Please help me overcome my (somewhat biassed) prejudice.
Expensive technology for the sake of lining the pockets of the manufacturers/retailers. Convince me.
Higher res screens are more expensive, due to the high pixel failure rate in manufacture. Lower res screens cater for the budget end of the market. Buyer beware. 😉
I'm not sure where the 780p came from ...
The only High Definition formats that I am aware of are based on 1080 lines (picture height) or 720 lines.
The 720p standard is actually 1280 pixels horizontal by 720 pixels vertical. The p stands for progressive scanning, which I think most people understand. I think this system has had some take up in the USA.
The 1080 system is 1920 pixels horizontal by 1080 pixels vertical, and can, depending on delivery requirements, be configured to be 24p, 25p, 50i, 30p, 60i, etc. This is the system currently implemented by, for example, Sky HD.
The 768 which Andrew queries arises because most 'HD Ready' screens are actually repackaged WXGA panels with a native resolution of 1366 x 768 pixels. Any video that has to be displayed on these screens has to be up-rezed from 720 x 576 (normal PAL) or down rezed from 1920 x 1080 HD. This, naturally has quite an impact on the quality.
These panels are also, I believe, by definition (no pun intended), progressively scanned - usually at a frequency between 70Hz to 80 Hz. This also requires, as part of the transcoding 'engine', a method of reformatting the motion information, to take account of a) interlace, and b) the difference in scanning frequency: e.g. 50i to 75p. This again, can have quite an impact on quality. The pixel response time on these screens can also sometimes be quite slow.
Some screens with a native resolution of 1920 x 1080 are becoming available in the UK. The difference in quality between these, and the inferior 1366 x 768 panels would make you choke!
Regards,
Ian.
The only High Definition formats that I am aware of are based on 1080 lines (picture height) or 720 lines.
The 720p standard is actually 1280 pixels horizontal by 720 pixels vertical. The p stands for progressive scanning, which I think most people understand. I think this system has had some take up in the USA.
The 1080 system is 1920 pixels horizontal by 1080 pixels vertical, and can, depending on delivery requirements, be configured to be 24p, 25p, 50i, 30p, 60i, etc. This is the system currently implemented by, for example, Sky HD.
The 768 which Andrew queries arises because most 'HD Ready' screens are actually repackaged WXGA panels with a native resolution of 1366 x 768 pixels. Any video that has to be displayed on these screens has to be up-rezed from 720 x 576 (normal PAL) or down rezed from 1920 x 1080 HD. This, naturally has quite an impact on the quality.
These panels are also, I believe, by definition (no pun intended), progressively scanned - usually at a frequency between 70Hz to 80 Hz. This also requires, as part of the transcoding 'engine', a method of reformatting the motion information, to take account of a) interlace, and b) the difference in scanning frequency: e.g. 50i to 75p. This again, can have quite an impact on quality. The pixel response time on these screens can also sometimes be quite slow.
Some screens with a native resolution of 1920 x 1080 are becoming available in the UK. The difference in quality between these, and the inferior 1366 x 768 panels would make you choke!
Regards,
Ian.
Hi,
There is a lot of confusion with HDTV.
Firstly, you must bear in mind that with standard definition, of those 625 horizontal lines, 50 are not visible. These are used during the Vertical Blanking Interval, or VBI, to sync the TV to the top of the field/frame. Its also used to contain teletext and other things, if present.
So, SD is actually only 575i, if you like (its typical resolution is 720x576).
With progressive scan (and this is were I have been confused) you gain vertical resolution, and it is especially apparent with movement. Imagine a football being kicked and moving up the screen fast enough that the image between field is different (a field is and interlace field, a 50th of a second in the UK). If this happens, you lose detail.
Progressive scan improves this. I can't remember the figures, but its about an equivalent 20-30% improvement in 'apparent vertical resolution' - if you like.
So if you take these two factors into account, you're effectively comparing 575i to 864i.
Also, you must be aware that HDTV has a far greater colour resolution as well. So the colours are more realistic, and the higher pixel resolution makes colour graduation smoother.
I believe that even progressive scan is still 25 fps, but the refresh rate can change.
MPEG4/h264 compression is scalable, so the decoder in the HDSTB or HDDVD can target its output to either 720 or 1080 lines. There is no upscaling/downscaling required afterwards.
The improvement from 625 lines to 720p is great. It really looks good. But I have also seen 1080i as well, and the jump in quality is the same again.
1080 line broadcasts are already occuring, its just the TVs are too expensive to market in the UK at the moment.
Cheers,
Phil
There is a lot of confusion with HDTV.
Firstly, you must bear in mind that with standard definition, of those 625 horizontal lines, 50 are not visible. These are used during the Vertical Blanking Interval, or VBI, to sync the TV to the top of the field/frame. Its also used to contain teletext and other things, if present.
So, SD is actually only 575i, if you like (its typical resolution is 720x576).
With progressive scan (and this is were I have been confused) you gain vertical resolution, and it is especially apparent with movement. Imagine a football being kicked and moving up the screen fast enough that the image between field is different (a field is and interlace field, a 50th of a second in the UK). If this happens, you lose detail.
Progressive scan improves this. I can't remember the figures, but its about an equivalent 20-30% improvement in 'apparent vertical resolution' - if you like.
So if you take these two factors into account, you're effectively comparing 575i to 864i.
Also, you must be aware that HDTV has a far greater colour resolution as well. So the colours are more realistic, and the higher pixel resolution makes colour graduation smoother.
I believe that even progressive scan is still 25 fps, but the refresh rate can change.
MPEG4/h264 compression is scalable, so the decoder in the HDSTB or HDDVD can target its output to either 720 or 1080 lines. There is no upscaling/downscaling required afterwards.
The improvement from 625 lines to 720p is great. It really looks good. But I have also seen 1080i as well, and the jump in quality is the same again.
1080 line broadcasts are already occuring, its just the TVs are too expensive to market in the UK at the moment.
Cheers,
Phil
Hi,
thanks Digi & Phil.
Your explanations are making the picture clearer.
So 768 screens are a waste of money. Is that the correct conclusion?
575line to 720line is a significant improvement. right/wrong?
720line to 1080line is a significant improvement. right/wrong?
p is better than i for fast moving images. right/wrong?
HDTV transmissions will be viewable at best resolution on either 768screens or 1080screens since the compression is scaleable. right/wrong?
Why is it necessary to up rez a 720line image to 768line image?
Can this be over-ridden to display @ 720 and just leave 24blank lines at top & bottom. I want circular objects to remain circular.
I am sure there is more to add.
Keep it coming.
thanks Digi & Phil.
Your explanations are making the picture clearer.
So 768 screens are a waste of money. Is that the correct conclusion?
575line to 720line is a significant improvement. right/wrong?
720line to 1080line is a significant improvement. right/wrong?
p is better than i for fast moving images. right/wrong?
HDTV transmissions will be viewable at best resolution on either 768screens or 1080screens since the compression is scaleable. right/wrong?
Why is it necessary to up rez a 720line image to 768line image?
Can this be over-ridden to display @ 720 and just leave 24blank lines at top & bottom. I want circular objects to remain circular.
I am sure there is more to add.
Keep it coming.
You pay your money .....
Current price for a Sony KDL 46X2000 (1920x1080) is approx GBP3400
Current price for a Sony KDL 46S2010 (1366x768) is approx GBP2000
Personally I'm waiting for 1920x1080 to stabilise at a reasonable price.
Regards,
Ian
Personally, I'm waiting for all of it to stabilise in price 🙂
There is a big difference between SD (625i) and 720p. There is also a big difference between 720p and 1080i, and of course (although you can't buy them cheaply) 1080p is cracking!
I don't think you'd miss the 48 missing lines. I think they'll end up under the cabinet work as overscan lines. They're not upscaled.
We have a 720p and a 1080i side by side at work, and the difference is stunning.
I think the best thing to do is expose yourself to some HD, this is getting easier in show rooms now. Bear in mind you'll need to be happy with SD performance too, HD can be quite revealing in that sense. HDTV kit is far from commodity, so there are huge differences between setups and needs a lot of reviewing.
Also beware, this is digital telly, even with HD, the compression ratios used greatly affect quality. I have seen some stunning pictures, but I have also seen some disappointing, highly compressed stuff too. Show room stuff might be better quality than what you might receive (but the Sky and BBC stuff to date looks good so far).
Cheers,
Phil
There is a big difference between SD (625i) and 720p. There is also a big difference between 720p and 1080i, and of course (although you can't buy them cheaply) 1080p is cracking!
I don't think you'd miss the 48 missing lines. I think they'll end up under the cabinet work as overscan lines. They're not upscaled.
We have a 720p and a 1080i side by side at work, and the difference is stunning.
I think the best thing to do is expose yourself to some HD, this is getting easier in show rooms now. Bear in mind you'll need to be happy with SD performance too, HD can be quite revealing in that sense. HDTV kit is far from commodity, so there are huge differences between setups and needs a lot of reviewing.
Also beware, this is digital telly, even with HD, the compression ratios used greatly affect quality. I have seen some stunning pictures, but I have also seen some disappointing, highly compressed stuff too. Show room stuff might be better quality than what you might receive (but the Sky and BBC stuff to date looks good so far).
Cheers,
Phil
Sorry, forgot to add.
I don't think 720p is a waste of money.
I've seen some reasonable LG 42" plasmas reach the £1500 mark recently and, one day, that might be an affordable path to HD for me for instance (and then the next TV might be an affordable 1080i/p in a few years time).
I think I prefer a Sony or Panicsonic reach that sort of price though.
Again, its a waste of money to you if you buy one and you don;t think its much better than SD, but you have to assess that yourself by testing.
I don't think 720p is a waste of money.
I've seen some reasonable LG 42" plasmas reach the £1500 mark recently and, one day, that might be an affordable path to HD for me for instance (and then the next TV might be an affordable 1080i/p in a few years time).
I think I prefer a Sony or Panicsonic reach that sort of price though.
Again, its a waste of money to you if you buy one and you don;t think its much better than SD, but you have to assess that yourself by testing.
Phil is absolutely correct when he states:
I agree that both Sky HD and BBC HD transmissions look very impressive on a 'proper' 1920x1080 screen - but BlueRay or HD DVD will be the highest quality HD that you'll see in the home. When these units become freely available, then comparative demos will become more valid in the retail situation.
Regards,
Ian
I agree that both Sky HD and BBC HD transmissions look very impressive on a 'proper' 1920x1080 screen - but BlueRay or HD DVD will be the highest quality HD that you'll see in the home. When these units become freely available, then comparative demos will become more valid in the retail situation.
Regards,
Ian
Thankyou all, for your time and information.
I have a handle on the issues and will probably come back when I've watched the market settle in a bit. 😉
Bye for now.
I have a handle on the issues and will probably come back when I've watched the market settle in a bit. 😉
Bye for now.
AndrewT said:
It also benefits whoever owns the airwaves. Digital HD broadcasts contain more data but take less bandwidth to broadcast than analog signals. In the USA, our heroes in Congress are probably salivating thinking of who will get the biggest bribe to be able to buy that broadcast bandwidth.
I agree there is a lot of money in digital TV, I see very little of it indeed, but at least it gives me a job I suppose.
At least this pocket lining can't last forever. For instance, standard definition STBs are now commodity, just like DVD players. The margins are terrible.
This will happen to HD in 10 years time - when the next big thing is talked about.
At least this pocket lining can't last forever. For instance, standard definition STBs are now commodity, just like DVD players. The margins are terrible.
This will happen to HD in 10 years time - when the next big thing is talked about.
Hi,
if my new (now one year old) TV has to wait ten years to be replaced I will probably not be able to see the improvement that HDTV can bring.
if my new (now one year old) TV has to wait ten years to be replaced I will probably not be able to see the improvement that HDTV can bring.
resolution
Be careful when you just compare "resolution" of NTSC/PAL versus HDTV formats. The number of lines & horizontal pixels being quoted for the Standard Definition (SD) formats are the luminance resolution (IE. white versus black). The number of color pixels that can be encoded on a single scan line are MUCH MUCH lower! (Do a little web searching and you will be stunned at just how low they are.)
I think the HD formats can have the color resolution at either 1/2 or 1/4 the luminance resolution. That is a vast improvement over SD, and the effect is stunning even with 720p.
I have a $700 US Vizio 32" LCD and a good UHF antenna & preamp. I am getting 32 different subchannels from Los Angeles (about 85 miles away) and the results are terrific. Some of the stations use 1080i and some use 720p, but even on the secondary subchannels where they center 480i 4:3 material between black side bars and scale it up to fit their equipment format I can still read the finest text fonts. That would be impossible with an SDTV.
Be careful when you just compare "resolution" of NTSC/PAL versus HDTV formats. The number of lines & horizontal pixels being quoted for the Standard Definition (SD) formats are the luminance resolution (IE. white versus black). The number of color pixels that can be encoded on a single scan line are MUCH MUCH lower! (Do a little web searching and you will be stunned at just how low they are.)
I think the HD formats can have the color resolution at either 1/2 or 1/4 the luminance resolution. That is a vast improvement over SD, and the effect is stunning even with 720p.
I have a $700 US Vizio 32" LCD and a good UHF antenna & preamp. I am getting 32 different subchannels from Los Angeles (about 85 miles away) and the results are terrific. Some of the stations use 1080i and some use 720p, but even on the secondary subchannels where they center 480i 4:3 material between black side bars and scale it up to fit their equipment format I can still read the finest text fonts. That would be impossible with an SDTV.
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