What is 1080i?

[dobyblue]

Originally Posted by welwynnick

Why shouldn't it?

The fields taken from successive frames have to be refreshed two times and three times respectively. That's what causes judder.

Nick

I think he means if it's reverted back to 1080p24 correctly it won't cause judder on devices that correctly display 24Hz at a rate divisible by 24, not including the 120Hz sets that do 3:2 to get to 60Hz then 2:2 to 120Hz.

[syncguy]

Judder shouldn’t be introduced due to the 1080i connectivity. If 1080/24p (e.g. blu-ray movie) is transmitted over a 1080i link, judder will not be introduced if the display decodes and displays the picture correctly.

As given previously, 24p could be transmitted in half frames via 1080i link. To do this 24p frames should be mapped on to 1080/60i, by repeating 2 and 3 field sequences. If this field sequence is displayed without correct decoding at 60 Hz, then, yes, of course you would get judder. However, if it is decoded correctly and remove excessive fields and reconstruct the original 24p picture and displays on a 24, 48, 72 … Hz display you will not get judder.

I have just tested this on PS3 and Sony VW60 projector. I watched a movie sequence at 24Hz and then repeated it after setting PS3 to transmit the same sequence at 1080i. The VW60 shows 24 p when PS3 transmits at 24p and 60i when PS3 transmits 60i. However, I couldn’t see any judder when it was on 1080i mode, I think this is due to the vw60 detecting the incoming 1080i signal and carrying out inverse telecine before displaying probably at 24 or 48 Hz.

However, I could see some difference in the picture in these two modes and I preferred the picture when it was set to 24p.

Also wish to note that if the original was 1080p (PS3 game), and if transmitted via 1080i, then it is not possible to reconstruct the original (without judder) because half of original information is lost (as indicated in one of my previous emails).

[dobyblue]

Don't a number of PS3 games run at 1080p30 though?

[welwynnick]

Originally Posted by syncguy

Judder shouldn’t be introduced due to the 1080i connectivity. If 1080/24p (e.g. blu-ray movie) is transmitted over a 1080i link, judder will not be introduced if the display decodes and displays the picture correctly.

As given previously, 24p could be transmitted in half frames via 1080i link. To do this 24p frames should be mapped on to 1080/60i, by repeating 2 and 3 field sequences. If this field sequence is displayed without correct decoding at 60 Hz, then, yes, of course you would get judder. However, if it is decoded correctly and remove excessive fields and reconstruct the original 24p picture and displays on a 24, 48, 72 … Hz display you will not get judder.

I have just tested this on PS3 and Sony VW60 projector. I watched a movie sequence at 24Hz and then repeated it after setting PS3 to transmit the same sequence at 1080i. The VW60 shows 24 p when PS3 transmits at 24p and 60i when PS3 transmits 60i. However, I couldn’t see any judder when it was on 1080i mode, I think this is due to the vw60 detecting the incoming 1080i signal and carrying out inverse telecine before displaying probably at 24 or 48 Hz.

However, I could see some difference in the picture in these two modes and I preferred the picture when it was set to 24p.

Some big "IFs" there.

Yes, so 1080i is fine if the display is perfect.

But even the VW60 isn't perfect, and most displays are not as good as that.

Most current 1080p displays don't do inverse telecine of 1080i60, let alone 1080i50 (for the rest of the World).

Even those that do, de-interlace 1080i60 to 1080p60, and display it as such.

And those few that de-interlace 1080i60 to 1080p24 don't do it perfectly. Even Gennum and Realta processors drop the cadence sometimes, so it's not a lossless process.

I agree its not impossible to perform IVTC on 1080i60 to an acceptable standard, but it can't be better than 1080p24 direct, and I don't think its fair to say that most displays can do it properly.

Nick

[dobyblue]

The KURO 1080p plasmas pass all deinterlacing and 3:2 tests, for those interested.

Gary Merson does extensive tests on all the sets he tests and they're always posted at www.hometheatermag.com or at www.hdguru.com

[syncguy]

Originally Posted by dobyblue

Don't a number of PS3 games run at 1080p30 though?

Probably. In this case, it will not be bad as 1080/60p when transmitted over 1080/60i (provided it is decoded and displayed correctly).

[syncguy]

Originally Posted by welwynnick

Some big "IFs" there.

Yes, so 1080i is fine if the display is perfect.

But even the VW60 isn't perfect, and most displays are not as good as that.

Most current 1080p displays don't do inverse telecine of 1080i60, let alone 1080i50 (for the rest of the World).

Even those that do, de-interlace 1080i60 to 1080p60, and display it as such.

And those few that de-interlace 1080i60 to 1080p24 don't do it perfectly. Even Gennum and Realta processors drop the cadence sometimes, so it's not a lossless process.

I agree its not impossible to perform IVTC on 1080i60 to an acceptable standard, but it can't be better than 1080p24 direct, and I don't think its fair to say that most displays can do it properly.

Nick

Okay. Surely, native 24p is be better than 1080/60i transmission. I could see a difference between 60i and 24p transmissions and unarguably I will choose the 24p.

[Ben123]

Originally Posted by dobyblue

There is no difference in resolution between 1080i and 1080p, they're both identical. That is to say, they both contain 1080 lines of vertical information, the only difference is how they are delivered. Agreed on the last sentence though - it's vital for 1080i.

Bingo! That's exactly why I see absolutely no difference between 1080i and 1080p output from my PS3 on my plasma.

[U4K61]

Originally Posted by Ben123

Bingo! That's exactly why I see absolutely no difference between 1080i and 1080p output from my PS3 on my plasma.

1080i is not an efficient carrier of 24p material. There is more notational overhead and six repeat frames - wasted space. It's a shame this is not used in the broadcast world. The extra bits could have been used for better PQ, metadata, or some other purpose. 24p and 30p were part of the origional 18 8VSB ATSC MPEG-2 High Def formats.

1080i did made sense at the time of the HD rollout. The analoge tube was timed to 60cycle AC.

[syncguy]

Originally Posted by Craig Ruchman

In the end though, 1080i is not an efficient carrier of 24P material. There is more notational overhead and repeated frames - wasted space. It's a shame this is not used in the broadcast world. The extra bits could have been used for better PQ or for some other purpose. 24P and 30P were part of the origional 18 8VSB ATSC MPEG-2 High Def formats.

Yes, 1080i is not efficient when carrying 24p but it can do this satisfactorily and it is possible to reconstruct the 24p frame sequence. Surely, 1080/24p is better than 1080/60i for some content types. However, it looks like the manufactures of the transmission/conversion equipment have not considered this possibility. I wonder why.

[welwynnick]

I guess we have to blame legacy CRT HDTVs for that particular standard. For 1080 line displays, I think interlaced scanning was inevitable as HD video processing and domestic progressive scan HDTVs were too expensive at the time the standards were set.

More's the shame, as digital compression of progressive video is much more efficient (at high levels of compression) than for interlaced video. Interlacing (like component sub-sampling) is only a simple form of compression that loses significant quality for a small degree of compression. The bandwidth/bit-budget would probably have been better spent with optimal compression of progressive video instead. Especially with films.

Nick

[syncguy]

They should have thought outside the box and consider possible future technology evolution scenarios. I think that the top-brains of the world get together on standards forums to make these decisions.

[sleazypig]

Originally Posted by Blu_Ray_Fan

They really don't use it anymore... 1080p is the new standerd and it's great!

most television brodcasts are 1080i (some are 720p) 1080i tvs are being phased out for in favor of 1080p or cheaper 720p sets. The manufactors are doing this so there is a bigger gap in pic quality between lower models then higher models. 1080i is better than 720p. Don't listned to the fud about 720p being better than 1080i. 1080p has the same resolution but without the blurring.

[tonydicenso]

Originally Posted by Homura

best description i've read

you must not read much

[tonydicenso]

Originally Posted by Blu_Ray_Fan

They really don't use it anymore... 1080p is the new standerd and it's great!

moron

[Ben123]

Originally Posted by Craig Ruchman

In the end though, 1080i is not an efficient carrier of 24P material. There is more notational overhead and repeated frames - wasted space. It's a shame this is not used in the broadcast world. The extra bits could have been used for better PQ, metadata, or some other purpose. 24P and 30P were part of the origional 18 8VSB ATSC MPEG-2 High Def formats.

I thought 1080p requires more bandwidth to carry than 1080i? Thats why it is not yet adopted in broadcasting since there is not enough bandwidth. From what I read so far, if the display is capable of de-interlacing properly, there is no difference.

[MatintheHat]

Originally Posted by tonydicenso

you must not read much

Originally Posted by tonydicenso

moron

Got coffee? Dude, your posts until now have all been spirited and positive additions to the forum. Don't muck up your cred trash talking other members. Remember what mother said, "If you can't say anything nice then don't say anything at all". Now back to the forum.

[dialog_gvf]

Originally Posted by Ben123

I thought 1080p requires more bandwidth to carry than 1080i? Thats why it is not yet adopted in broadcasting since there is not enough bandwidth. From what I read so far, if the display is capable of de-interlacing properly, there is no difference.

Bandwidth is measured in bits per second. So, the frame rate as well as the resolution are factors when discussing bandwidth.

ATSC defines 1080/24p, 1080/30p, and 1080/60i

In fact, 1080/24p requires LESS bandwidth than 1080/30p and 1080/60i, which have the identical bandwidth.

The next level people are interested in (mostly for sports) is 1080/60p. Currently 1080/60p itself (even though many players output it) doesn't gain us anything. There is no source of 60p content at this time.

And you're right, the current broadcast (OTA, cable and sat) don't have enough bandwidth in a channel to carry that. Neither does the current Blu-ray specs.

Gary

[dialog_gvf]

Incidently, and alternative to upgrading your HDTV if it doesn't de-interlace properly but does handle a 60p input is to get an outboard video processor of some kind.

A constructive and value choice right now are the Onkyo 875 and 905 receivers that have an HQV processor (Reon) in them. So, if you thinking about getting a new receiver anyway (for HDMI and 7.1) then that is an option open to you.

Gary

[U4K61]

Originally Posted by Ben123

I thought 1080p requires more bandwidth to carry than 1080i? Thats why it is not yet adopted in broadcasting since there is not enough bandwidth. From what I read so far, if the display is capable of de-interlacing properly, there is no difference.

1080p/60 does. However 1080p/24 uses less space then 1080i/60 which is equivalent to 30fps - an extra 6 frames. 1080i/60 was chosen over the more efficient 1080p/24 because of interlaced analogue and 60 cycle AC current and because early HD sets capable of 720p or higher were few and far between. We needed some kind of bridge to digital when OTA MPEG2 transmission began in the 90's, so 1080i worked well with analogue CRT tube and projection.

1080i sourced from 24fps film can be de-interlaced back to 1080p. So 1080i = 1080p PQ in that case.