New 1080p tv - output 720p or 1080i?

[TyroneShoes]

Originally Posted by stevel

The better TVs buffer and combine the two "scans" to form a 1080p frame for display. The scans are at 60Hz, combining to form 1080p at 30Hz. With 720p, you get 720p at 30Hz. Which is better? You tell me...

OK, but the answer is far from simple. For true 1080p acquisition, a 1080p set would be better. For 1080 acquisition that does not preserve the time relationships between the separate fields, a 1080p set would also be better. 1080p sets are typically better than any other choice, all else being equal, for all content. The rare exception might be 720p content, which implies at least a rescaling, and would not on a 720-native set. But rescaling is not very destructive, so its effect is probably negligible, even there. 1080p sets are new enough to probably all do deinterlace properly, too.

But not everyone can afford a 1080p set, not everyone bought a 1080p set (many buying before they were available), and not everyone even wants a 1080p set.

That about covers resolution and rescaling, but not motion artifacting. And it's actually 720p/60. 60 unique fields/frames a second, each field/frame providing 720 lines (this also explains why the pixel delivery rate is about 5/6ths of that for 1080i, and why 720p signals need slightly less bandwidth than 1080i for the same level of quality, another reason being that compression of interlaced signals is not as efficient). 1080 provides 60 fields, each composing half of a frame (every other line) for only 30 frames a second. At that point the scan rate of a 1080-native set is half that of a 720p set. Is that better? You tell me...

A 1080p set can double the scan rate to 60 if it is designed that way, which means it repeats each reinterlaced field twice. That will reduce flicker to the same level as a native 720p set, but might introduce slight motion judder. IOW, a moving object will be represented in a unique X/Y position 60 times a second for 720p, but only 30 times a second even at a 60 Hz scan rate for 1080p. Is that better? Maybe not, but for either delivery method, the 1080p set will still be better in most aspects. There is no trade-off or downside to a 1080p set compared to any other set, other than the price.

The gurus at ABC have gone on record very convincingly as to why they believe 720p delivery is superior, and it's not just spin. If they thought 1080i was better, nothing was stopping them, or FOX or ESPN, from choosing that delivery method. But they chose 720p instead, primarily because of less motion artifacting.

But true 1080p display technology shoots a few holes in their theory. 1080i delivery of 1080i content to a set that doesn't reinterlace properly is significantly inferior to 720p delivery of 720p content when there is high motion, but 1080i delivery of 1080p content to a 1080p set that does proper deinterlace is only slightly inferior to 720p delivery of 720p content when there is high motion, unless the bandwidth is restricted. When there is no high motion, true 1080i rules due to it's higher resolution, to sets with a greater than 720 native rez, anyway, and that deinterlace properly. And if a 1080p set simply reinterpolates 720p to 1080p, it will have the same freedom from motion artifacting (not to be confused with compression artifacting) for 720p content that any 768 or 720 set enjoys.

So, a 1080p set is better in almost every way, generally speaking. But it is not superior in every way, and it is not significantly better in some of the ways it actually is superior. But it is significantly superior in some critical ways. After seeing how a SXRD handles all content, especially SD content, I would never today buy anything less than that level of technology. I just wish that was available in October, 2004, although even today it is significantly more costly than the state of art was then.

[jschmidt]

Originally Posted by TyroneShoes

If the deinterlace is not done correctly, static images in 1080i have less potential V resolution than static images in 720p. If the interlace IS done properly, static images in 1080i have more potential V resolution than 720p. Moving images in 1080i have less potential V rez than moving images in 720p, regardless of the deinterlace used (about 500 lines under the best of circumstances). But 1080i (non DTV, anyway) has more potential H rez than 720p, regardless of the deinterlace, and regardless of whether the images are static or dynamic. 1080i from 1080p source content, deinterlaced properly, can preserve about 750 lines of effective V rez, which is the best available, and of course it also preserves all of the H rez. That is one case where 720p will not look better.

I have read some of the disagreements with my statements. Allow me to clarify. De-interlacing works. No doubt about it... if you have a 1080p set that de-interlaces well, you can achieve 1080 lines of resolution, but at only 30 frames per second. 720p is 60 frames per second. It is 720 lines of resolution every 1/60 of a second. 1080i (even properly de-interlaced to 1080p) is still only 540 lines of resolution every 1/60 of a second. Some people prefer the picture of 720p for this reason. More frames per second = better ability to capture fast-moving action. It's better for sports and video games. Some people prefer 1080i for film content. My point is that you have to take into account the remporal resolution (number of frames per second) as well as the spacial resolution (number of pixels). Right now, it is not possible for existing interconnects (even on the pro market) to handle 1080p uncompressed. It requires something like 10Gb per second bandwidth, which we don't have yet. I don't think we'll see true, native 1080p content being fed to our HDTVs for quite some time.

[AbMagFab]

Originally Posted by TyroneShoes

OK, but the answer is far from simple. For true 1080p acquisition, a 1080p set would be better. For 1080 acquisition that does not preserve the time relationships between the separate fields, a 1080p set would also be better. 1080p sets are typically better than any other choice, all else being equal, for all content. The rare exception might be 720p content, which implies at least a rescaling, and would not on a 720-native set. But rescaling is not very destructive, so its effect is probably negligible, even there. 1080p sets are new enough to probably all do deinterlace properly, too.

But not everyone can afford a 1080p set, not everyone bought a 1080p set (many buying before they were available), and not everyone even wants a 1080p set.

That about covers resolution and rescaling, but not motion artifacting. And it's actually 720p/60. 60 unique fields/frames a second, each field/frame providing 720 lines (this also explains why the pixel delivery rate is about 5/6ths of that for 1080i, and why 720p signals need slightly less bandwidth than 1080i for the same level of quality, another reason being that compression of interlaced signals is not as efficient). 1080 provides 60 fields, each composing half of a frame (every other line) for only 30 frames a second. At that point the scan rate of a 1080-native set is half that of a 720p set. Is that better? You tell me...

A 1080p set can double the scan rate to 60 if it is designed that way, which means it repeats each reinterlaced field twice. That will reduce flicker to the same level as a native 720p set, but might introduce slight motion judder. IOW, a moving object will be represented in a unique X/Y position 60 times a second for 720p, but only 30 times a second even at a 60 Hz scan rate for 1080p. Is that better? Maybe not, but for either delivery method, the 1080p set will still be better in most aspects. There is no trade-off or downside to a 1080p set compared to any other set, other than the price.

The gurus at ABC have gone on record very convincingly as to why they believe 720p delivery is superior, and it's not just spin. If they thought 1080i was better, nothing was stopping them, or FOX or ESPN, from choosing that delivery method. But they chose 720p instead, primarily because of less motion artifacting.

But true 1080p display technology shoots a few holes in their theory. 1080i delivery of 1080i content to a set that doesn't reinterlace properly is significantly inferior to 720p delivery of 720p content when there is high motion, but 1080i delivery of 1080p content to a 1080p set that does proper deinterlace is only slightly inferior to 720p delivery of 720p content when there is high motion, unless the bandwidth is restricted. When there is no high motion, true 1080i rules due to it's higher resolution, to sets with a greater than 720 native rez, anyway, and that deinterlace properly. And if a 1080p set simply reinterpolates 720p to 1080p, it will have the same freedom from motion artifacting (not to be confused with compression artifacting) for 720p content that any 768 or 720 set enjoys.

So, a 1080p set is better in almost every way, generally speaking. But it is not superior in every way, and it is not significantly better in some of the ways it actually is superior. But it is significantly superior in some critical ways. After seeing how a SXRD handles all content, especially SD content, I would never today buy anything less than that level of technology. I just wish that was available in October, 2004, although even today it is significantly more costly than the state of art was then.

Nice explanation. And yes, the SXRD is a nice set

[zooie123]

Hey all,

Thanks for so many informative responses. I have hooked all up and played for about 3 hrs with all equipment.

xbox360 - component 2, 1080i - works great, no lag in high action games, much better than 720p set

Samsung HT in a box - component 1 - 480p - looks fantastic, much better than 720p set

Hr10-250, hdmi, 1080i - regular sd channels look better than 720p set, HD content so far from 70-79 channels, a tad better, have not tried OTA yet.

All in all, I will play between 1080i and 720p output from dvr, but so far 1080i looks great. I am so happy with my purchase.

Thanks again all.

[TyroneShoes]

Originally Posted by jschmidt

...Right now, it is not possible for existing interconnects (even on the pro market) to handle 1080p uncompressed. It requires something like 10Gb per second bandwidth, which we don't have yet. I don't think we'll see true, native 1080p content being fed to our HDTVs for quite some time.

I agree, and I think it's for a couple of reasons. The biggest reason is that 1080p sets can already reconstruct true 1080p content from 1080i broadcasts, so there is no advantage to ever broadcasting 1080p content as 1080p.

Another reason is because the broadcast industry moves at a glacial pace. We've had HD as a glimmer in our eyes since the early 80's, finally started to actively pursue it in the mid 90's, and here we are finally just beginning to implement it in a semi-serious way a decade after that. There has to be a motivating factor, and eating more precious bandwidth for no increase in content is just the opposite of that. Unfortunately, the factors that motivate the providers of HD are factors that are more likely to chip away at available bandwidth.

1080p as acquired takes only about 1.5 Gbps (only!). But that's still a lot of data, especially when the pipe is not very large, and it is impractical to widen the pipe very much at all. There is a finite amount of data that can be sent through a 6 MHz channel, and that is about 20 Mbps. A closed system can transmit about twice that much, because it doesn't need the overhead and reduncancy requuirements of a terrestrial OTA channel. But the providers are motivated to transmitting as few bits as they can get away with, regardless of what is technically possible. Uncompressed HD just doesn't exist for consumers, or outside of acquisition.

I actually don't ever expect to see 1080p content delivered as 1080p, either OTA or from other vendors. What we will see is more efficient ways of sending less information to represent more information. MPEG-4 is a perfect example of that. HD will get incrementally better, and there will be less "bad" HD as we go along, but don't expect bandwidth to never become precious, or major PQ improvements. Displays will improve a bit more than the content itself will, and they will become more reliable and less costly, but the change from SD to HD as we know it today is the most dramatic improvement we can expect to see in our lifetimes.

[guyricardo]

Originally Posted by TyroneShoes

I agree, and I think it's for a couple of reasons. The biggest reason is that 1080p sets can already reconstruct true 1080p content from 1080i broadcasts, so there is no advantage to ever broadcasting 1080p content as 1080p.

I'm just trying to understand this point. If I've been following all this info correctly, ins't that reconstructed 1080p signal actually a 'doubled' 1080i? Meaning that they take two halfs of the 1080i signal and put them back together (deinterlacing?), then repeat that twice at 1/60s. If this is the case, I can see why it would be superior for slow moving or static images, but for faster motion, its still only producing 30 unique 1080p images per second, as opposed to 60 720p images?

I have no idea which would actually be better. I'm very happy with my 768 set. I keep the box on 720p, and alot of my programs are action and sports on ABC/Fox/ESPN. I've never really noticed any advantage in haveing it at 1080i, but maybe it's time to experiment again, especially now that I've added an A/V reciever in between.

Bottom line I take from all this is that if you're buying a new HDTV, 1080p would be better overall, and trust your own eyes as far as setting it up with all your other equipment.

....sorry for the ramble

[rcbray]

Originally Posted by TyroneShoes

You're right, rc. And according to that logic what you say would be the best choice for your set, at least. Now why don't you try it and report back to us on how much difference it makes, or doesn't make?

A native 720P signal fed to the SXRD is marginally better than allowing the HD Tivo to upconvert it to 1080i. Believe the HD Tivo's replacement will have a native mode which will be great. However, today the improvement is so slight (and the 1080i upconverted signal looks so good) that I just keep the Tivo on 1080i output unless I know I'm going to watch several hours of 720P. Then I may go to the effort of changing the Tivo output to 720P.

[whsbuss]

Originally Posted by rcbray

A native 720P signal fed to the SXRD is marginally better than allowing the HD Tivo to upconvert it to 1080i. Believe the HD Tivo's replacement will have a native mode which will be great. However, today the improvement is so slight (and the 1080i upconverted signal looks so good) that I just keep the Tivo on 1080i output unless I know I'm going to watch several hours of 720P. Then I may go to the effort of changing the Tivo output to 720P.

Same here on this end. I do watch Fox, ABC, ESPN sports events in 720p. But for normal viewing I just leave the Tivo in 1080i.

[TyroneShoes]

Originally Posted by guyricardo

I'm just trying to understand this point. If I've been following all this info correctly, ins't that reconstructed 1080p signal actually a 'doubled' 1080i? Meaning that they take two halfs of the 1080i signal and put them back together (deinterlacing?), then repeat that twice at 1/60s. If this is the case, I can see why it would be superior for slow moving or static images, but for faster motion, its still only producing 30 unique 1080p images per second, as opposed to 60 720p images?...

That is exactly right. For 1080p to be broadcast with any advantage over 1080i (or to have the lower motion artifacts of 720p) it would have to be broadcast at the higher frame rate. The prevailing acquisition format is 1080p/24 for film. Acquisition of video is typically at 1080p/30 (or 720p/60, I believe). This means that only if video were acquired (and post-produced) at a higher frame rate, such as 1080p/60, would it have the lower motion artifacting of 720p.

Of course broadcasting twice as many 1080 frames would take significantly more bandwidth, meaning the compression ratio would have to increase (because the bandwidth will be limited to 6 MHz probably forever, even on cable and satellite). So the tradeoff there would not be worth it at least up until the point where compression technology becomes much more sophisticated than anything available today.

We might see the higher frame rate for video acquisition eventually, and there is talk of shooting feature film at a true 48 fps. But unless these things come to pass, which is not likely on any large scale within the lifespan of every brand-new 1080p set that will be sold this year, that means that broadcast improvements will not likely be seen, and the DVD telecine transfers at 1080p will also not really be better than 1080i broadcasting, even for 1080p sets.

[TyroneShoes]

Originally Posted by rcbray

A native 720P signal fed to the SXRD is marginally better than allowing the HD Tivo to upconvert it to 1080i. Believe the HD Tivo's replacement will have a native mode which will be great...

There is talk of 6.2 coming next month, and that is supposed to allow a native pass-through for the HR10. We'll see. With any luck, this entire discussion will be moot.

[dogdoctor]

Originally Posted by TyroneShoes

There is talk of 6.2 coming next month

Really...where is that information coming from? That would be cool, although I have my doubts.

Originally Posted by TyroneShoes

supposed to allow a native pass-through for the HR10.

A bit OT so forgive me as I am new to a lot of the techincal terms. In short, would a native pass-through would allow 480i, 480p, 720p, 1080i signals to pass through the HR10 as 480i, 480p, 720p, and 1080i and then allow the HDTV to upscale, downscale depending? I assume the benefit of this is that the signal goes through less processing and less degredation? Please educate me. Thanks.

[HomieG]

Also, I'm pretty sure that the ATSC spec for HD does not include 1080p at 30fps. The bandwidth to broadcast at higher frame rates may also be an issue for 1080p (broadcast).

[DeDondeEs]

My TV has 720p native resolution, but if I switch my Tivo to 720p for some odd reason I get a slight headache when watching, no matter if it is 720p or 1080i programming. So I just leave it on 1080i. What could cause that? Perhaps the converter in my TV works better than the one in my Tivo. Also if something is broadcast in 720p and my TV is 720p native, does the TV still do anything to the signal coming across the HDMI or does it just pass through without conversion?

They should put a setting on the Tivo where it just passes through the resolution of the broadcast to your TV to up/down convert.

[RMSko]

Originally Posted by zooie123

Hey all,

Thanks for so many informative responses. I have hooked all up and played for about 3 hrs with all equipment.

xbox360 - component 2, 1080i - works great, no lag in high action games, much better than 720p set

Samsung HT in a box - component 1 - 480p - looks fantastic, much better than 720p set

Hr10-250, hdmi, 1080i - regular sd channels look better than 720p set, HD content so far from 70-79 channels, a tad better, have not tried OTA yet.

All in all, I will play between 1080i and 720p output from dvr, but so far 1080i looks great. I am so happy with my purchase.

Thanks again all.

You may want to set the Xbox 360 at 720p. I also have a Sammy 1080p set and although I set my HR10-250 at 1080i, I set my Xbox 360 at 720p. First, many of the games are made in 720p and not 1080i so you would be passing the native resolution to the TV if you use 720p. Also, with games, just as with sports, fast moving action seems to look better at 720p, at least to me. It may be a matter of preference, but others have also reported similar results.