Still a little confused about interlaced/progressive

[Hawknelson05]

I know the general ideas behind them that progressive tv's refresh all ixels at once and interlaced tv's alternate odd and even row refreshing. But between a 720p tv and a 1080i, wouldnt the progressive look a little better since it's refresh rate is faster? I had always thought there was no major difference in picture between 720p and 1080i, but now i dont know =(

[bkbluray]

Interlaced will give you 1080p detail (will flip through twice as many frames to produce it) through one 540p frame followed quickly by another. 720p will refresh all the pixels at once (like you said) so it will allow for smoother playback. Hope that helps.

EDIT: All 720p TV's also can do 1080i. My advice is use 1080i if you have a TV that has little or no motion blurring, and 720p with an LCD.

[Hawknelson05]

my TV is a 720p. So that wont do 1080i at all? My hd cable box says it's giving the tv a 1080i signal. so does this need to be changed to make the pic look better?

[kpkelley]

720P tv's are 1080i tv's. The only difference b/w 720p and 1080i is the lines of source information. 720P is 720 lines scanned progressively, while 1080i is the same information broken into 1080 lines. The more lines means a better image, while progressively scanning increases sharpness and fluidity of the image. That being said it is dependent upon the source material 1080p material will look better in 720p/1080i than 720p/1080i material b/c there is more information from the source. While 720p/1080i can be upconverted to 1080p images, it won't look as good as 1080p source material becuase of less source information.

[Hawknelson05]

word. thanks all

[welwynnick]

Very confusing.

Explanation to follow.

Nick

Edit: wife's birthday today - going to the theatre, sorry....

[gand41f]

Originally Posted by welwynnick

Very confusing.

Explanation to follow.

Nick

Still writing?

enjoy
gandalf

[Frode]

Read this:

http://www.hometheaterhifi.com/volum...07-part-1.html
http://hdguru.com/?p=187

In short: Stick to 720p unless you have a true 1080p set (or a HD CRT which can do 1080i native) for the input if you can.

[welwynnick]

Originally Posted by welwynnick

Edit: wife's birthday today - going to the theatre, sorry....

Just got back from seeing "Wicked" at the (London)Victoria Apollo, and by coincidence, in the street we bumped into my wife's oldest and closest friends from 250 miles away, who we hadn't seen for a year. A real million-to-one chance, so we just had to celebrate over some drinks. Hence my typeing....

Anyway, I was present-shopping yesterday and happened to pass by a farily high-end AV shop I hadn't seen before. What else could I do? They were showing all the Pioneer Kuro plasmas, which were nice, and I got chatting to akeen salesman. He described some the other LCD TVs as 1080i TVs, presumably as they accepted 1080i inputs, but not 1080p. He didn't seem to appreciate the difference beween input format and display format, so I thought if he didn't, then what shance do most of his customers stand?

For the avoidance of doubt, all digital displays (plasma, LCD, LCOS, DLP, SXRD, DILA, OLED, everything) are progressive displays. That means every line is refreshed with every screen refresh. CRT TVs and PJs generally use interlaced scanning, meaning every other line is refreshed (thought they can be progressive as well).

Other things being equal, progressive is better than interlaced, but it's not as simple as that when there are tangiable constraints such as bandwidth or bit-rate. HDTV can be 1080i or 720p, but it's very important to distinguish between the distribution format, the interface format, and the display format, as they can all be different.

For example, you could have an HD DVD with 1080i60 concert video on the disc (distribution) that is de-interlaced by the player to output 1080p60 (interface) and displayed on a TV with a native resolution of 720p (display). So what format is that?

Alternatively, an HDTV broadcast of a film that has been pulled up to 1080i60 may be successfully processed to 1080p24 without incurring any spatial or temporal resolution artifacts, and may look better than a 720p broadcast of the same film. That what Frode's reference-standard links were all about - what is possible with 1080i, and what can go wrong. 1080i CAN give you everything that 1080p does, but only where the processing and the display are upt to it. Many people assume that is the case, but it's not usually. That's not really anything to get up in arms about, as it's difficult and expensive to get right, just as it was with DVDs a generation ago - they got it pretty much right after a few years, and I'm sure HDTV will do in due course.

Sorry that's not really resolved much confusion, Nick

[corduroygt]

Originally Posted by welwynnick

Just got back from seeing "Wicked" at the (London)Victoria Apollo, and by coincidence, in the street we bumped into my wife's oldest and closest friends from 250 miles away, who we hadn't seen for a year. A real million-to-one chance, so we just had to celebrate over some drinks. Hence my typeing....

Anyway, I was present-shopping yesterday and happened to pass by a farily high-end AV shop I hadn't seen before. What else could I do? They were showing all the Pioneer Kuro plasmas, which were nice, and I got chatting to akeen salesman. He described some the other LCD TVs as 1080i TVs, presumably as they accepted 1080i inputs, but not 1080p. He didn't seem to appreciate the difference beween input format and display format, so I thought if he didn't, then what shance do most of his customers stand?

For the avoidance of doubt, all digital displays (plasma, LCD, LCOS, DLP, SXRD, DILA, OLED, everything) are progressive displays. That means every line is refreshed with every screen refresh. CRT TVs and PJs generally use interlaced scanning, meaning every other line is refreshed (thought they can be progressive as well).

Other things being equal, progressive is better than interlaced, but it's not as simple as that when there are tangiable constraints such as bandwidth or bit-rate. HDTV can be 1080i or 720p, but it's very important to distinguish between the distribution format, the interface format, and the display format, as they can all be different.

For example, you could have an HD DVD with 1080i60 concert video on the disc (distribution) that is de-interlaced by the player to output 1080p60 (interface) and displayed on a TV with a native resolution of 720p (display). So what format is that?

Alternatively, an HDTV broadcast of a film that has been pulled up to 1080i60 may be successfully processed to 1080p24 without incurring any spatial or temporal resolution artifacts, and may look better than a 720p broadcast of the same film. That what Frode's reference-standard links were all about - what is possible with 1080i, and what can go wrong. 1080i CAN give you everything that 1080p does, but only where the processing and the display are upt to it. Many people assume that is the case, but it's not usually. That's not really anything to get up in arms about, as it's difficult and expensive to get right, just as it was with DVDs a generation ago - they got it pretty much right after a few years, and I'm sure HDTV will do in due course.

Sorry that's not really resolved much confusion, Nick

only thing i want to add to your excellent description is that the only time 1080i can't give everything 1080p can't is (excluding sub-par video processing) when you have the source at more than 30 fps in a progressive format, like a 1080p video game running at 60fps.

[gand41f]

Originally Posted by corduroygt

only thing i want to add to your excellent description is that the only time 1080i can't give everything 1080p can't is (excluding sub-par video processing) when you have the source at more than 30 fps in a progressive format, like a 1080p video game running at 60fps.

Unfortunately this "sub-par" applies to something like 81% of the TVs.

http://www.hometheatermag.com/hookmeup/1107hook2/

enjoy
gandalf

[gand41f]

Originally Posted by welwynnick

For the avoidance of doubt, all digital displays (plasma, LCD, LCOS, DLP, SXRD, DILA, OLED, everything) are progressive displays.

Weren't the ALiS plasmas (1024x1080 or something) interlaced?

enjoy
gandalf

[Frode]

1024x1024, and yes they were interlaced, meaning you only got 1024x512 effective resolution.

[welwynnick]

Originally Posted by gand41f

Weren't the ALiS plasmas (1024x1080 or something) interlaced?

enjoy
gandalf

It was late when I wrote that, and I didn't want to go on for any longer than I had to, but I did wonder if someone would remember the ALIS panels. Whether they are interlaced or not has been debated to the ends of the World, without there being any authoritative explanation from Hitachi et al. There's no easy way unless you're much better with English than me (maybe not so unlikely).

My understanding is this. Plasmas display luminous intensity with a number of sub-frame illumination cycles of variable lengths within each video frame. The pixels are either on or off, and the brightness is modulated roughly in proportion to the duty cycle. The length of each cycle relates to a bit in the control word for each sub-pixel, and will be typically responsible for 1/2, 1/4 ...1/128 of the whole frame (more than 128 for 10 bits per colour etc )

Normal plasmas divide the screen up into a number of bands and switch them on and off together in accordance with the driving signal. ALIS panels drive odd and even rows of pixels alternately, rather like interlaced TV. However, with TV, the whole frame is divided into fields, but with ALIS, it's the sub-frames that are divided. So the physical display process is interlacing, but that is a lower, display level process than the video signal level process. The displayed video is still in progressive frames, but the display uses sub-frame level interlacing to display those progresseive frames. That's why I didn't mention it as an exception to other digital displays.

Hope that makes sense.

regards, Nick

[blukrank]

I know someone that has a 1080i CRT TV.And he has his Blu-Ray player set to 720p as 1080i gives him waves across the screen.Does anyone know what could be causing the waves?

[Frode]

Originally Posted by blukrank

I know someone that has a 1080i CRT TV.And he has his Blu-Ray player set to 720p as 1080i gives him waves across the screen.Does anyone know what could be causing the waves?

Cable problems - get better ones. In addition, most likely his TV is converting 720p to 1080i anyway, so he's losing out with his current setup.

[gand41f]

Originally Posted by welwynnick

It was late when I wrote that, and I didn't want to go on for any longer than I had to, but I did wonder if someone would remember the ALIS panels. Whether they are interlaced or not has been debated to the ends of the World, without there being any authoritative explanation from Hitachi et al. There's no easy way unless you're much better with English than me (maybe not so unlikely).

Maybe the problem is the original English translation. I looked at their Japanese site and found this:

http://www.hitachi-fhp.co.jp/pdp/fhp_pdp/pdp-bt201.html
http://www.hitachi-fhp.co.jp/pdp/fhp_pdp/pdp-bt202.html

The first page describes ALIS and the second page e-ALIS. It says e-ALIS is for larger screens but the example given only has 768 scan lines.

Originally Posted by welwynnick

My understanding is this. Plasmas display luminous intensity with a number of sub-frame illumination cycles of variable lengths within each video frame. The pixels are either on or off, and the brightness is modulated roughly in proportion to the duty cycle. The length of each cycle relates to a bit in the control word for each sub-pixel, and will be typically responsible for 1/2, 1/4 ...1/128 of the whole frame (more than 128 for 10 bits per colour etc )

The part I bolded answers one question I had regarding plasmas -- does the brightness of each pixel go down over time (like CRT) or does it stay the same (like LCD). From what you said, I believe it means it does go down, but not because of phosporus getting darker after the electron beam leaves it (like CRT) but rather because the electrical circuitry is designed to regulate the pixels' brightness to emulate the more CRT-like look, correct?

Originally Posted by welwynnick

Normal plasmas divide the screen up into a number of bands and switch them on and off together in accordance with the driving signal. ALIS panels drive odd and even rows of pixels alternately, rather like interlaced TV. However, with TV, the whole frame is divided into fields, but with ALIS, it's the sub-frames that are divided. So the physical display process is interlacing, but that is a lower, display level process than the video signal level process. The displayed video is still in progressive frames, but the display uses sub-frame level interlacing to display those progresseive frames. That's why I didn't mention it as an exception to other digital displays.

Hope that makes sense.

regards, Nick

Sort of. By "sub-frames", you mean either one progressive frame of 720/60p or one interlaced frame of 1080/60i (in either case, 1/60th of a second)? The e-ALIS figure in the second link above seems to indicate that, it says it uses two phases to show the entire field in 1/60sec so a frame is displayed in 1/30sec.

From what you said, assuming it's the e-ALIS, it seems like e-ALIS is essentially a 1024/120i device which uses two cycles of 1/120sec to display all the scan lines. So it needs 1024/60p as input to the panel itself, which I assume the circuitry first creates by scaling from 720/60p or deinterlacing from 1080/60i.

If that's not the case -- well I guess I'm still confused.

enjoy
gandalf