I am using a Sony VPL VW-50 connected by one single HDMI cable to my Yamaha V2700 amp. I have a PS3 connected to the V2700 via HDMI and a XBOX 360 connected via component cable. I can feed 1080p native signals to the Sony from the PS3 but the XBOX 360 can not send 1080p signals via the component cables. I've been doing some web research and am confused on this issue but seems to be either because of copyright protection not allowing 1080p to be sent via anything but a HDMI connection or a physical limitation of a component cable to carry a 1080p signal. Not really sure which it is but I do know that I can't get a 1080p signal from the HD DVD connected to the XBOX. I've read somewhere that a special VGA cable will allow you to send a 1080p signal from the XBOX 360 but that would mean stringing another cable to the projector which I'd like to avoid.

My question is which signal will give me a better picture on the Sony projector, 720p or 1080i? I've tried to view both to make a comparison but its difficult to truly gauge switching back and forth. Common sense tells me that the 720p gives you more pixels on any single scene compared to 1080i which is essentially only 540 lines on any given scene but I wasn't sure what magic the Sony projector did to the various signals.

Sorry for this newbie question but I've read the forums and done research and it seems that I can't find a straight answer. Hence I figured I would post on this forum as most of the users appear to be experts on this field. Thanks for any input you can provide.

My question is which signal will give me a better picture on the Sony projector, 720p or 1080i? I've tried to view both to make a comparison but its difficult to truly gauge switching back and forth.

The short answer is this: You should output 1080i from your HD DVD drive.

The longer answer is below.


Common sense tells me that the 720p gives you more pixels on any single scene compared to 1080i which is essentially only 540 lines on any given scene but I wasn't sure what magic the Sony projector did to the various signals.

One of the great mysteries of the universe is why so many people seem to think that 720p contains more resolution per frame than 1080i. In reality, 1080i and 1080p have the same resolution per frame, which is roughly twice that of 720p. The only difference between 1080i and 1080p is that one of these is interlaced (so the odd and even fields in a given frame are displayed one after the other, a fraction of a second apart), whereas the other is progressive (both odd and even fields are displayed at the exact same moment in time). In both cases, an actual frame contains roughly 2 million pixels, compared to the roughly 1 million of 720p. And the odd/even fields in a 1080i signal are displayed so rapidly that the mind sees them as one continuous image.

Of course, the Pearl cannot display a 1080i signal without first converting it to 1080p, since 1080p is the Pearl's native resolution.

The good news is that the Pearl does a very nice job of deinterlacing a 1080i film based signal, such as that from an HD DVD drive. In fact, the Pearl will take the 1080i film based content and deintelrace it to produce true 1080p frames.

Whether or not you will be able to see a difference will depend a lot upon your seating distance and the particular disc you're playing.

It's more accurate to say that the Pearl's native resolution is 1920x1080 and that it accepts video signals of 1080i, 1080p, 720p, 480p, etc., and converts them to its native signal format of 1080p when necessary.

It's more accurate to say that the Pearl's native resolution is 1920x1080 and that it accepts video signals of 1080i, 1080p, 720p, 480p, etc., and converts them to its native signal format of 1080p when necessary.

Are you saying this because I used the term "native resolution" instead of "native signal format?"

I hear Wikipedia is looking for an auditor... :D

P.S.

You are correct, of course. But if we wanted to talk about the Pearl's native signal format, we could get even more specific than merely stating 1080p, and the whole thing seems a bit like overkill in the context of this thread.

The short answer is this: You should output 1080i from your HD DVD drive.

The longer answer is below.



Thank you for the informative reply. As you state there is a lot of confusion around the various resolutions. As I originally stated I tried both the 720p and 1080i outputs and couldn't really see a difference but its difficult to do a true comparision with the long delay in flipping back and forth.

I'm still a little confused. Are you simply saying that a 1080i signal has more pixels than a 720p signal and therefore should provide a cleaner picture? I understand that the time between frames is so quick that the human eye really can't decipher but in reality for that fraction of a moment isn't the 1080i signal made up of 540 lines of data while the 720p is 720 lines of data?

In the end I'll take your suggestion and leave the output on 1080i.

Would I see a noticeable difference if I ran a VGA cable to the monitor and got native 1080p?

The math here is true for film based material (which virtually all HD DVD is), but it's a little more complicated when the material is video based.

HD video that is 720p (ESPN sports) is 60 frames per second, so:

1280x720x60=55,296,000 pixels per second.

HD video that is 1080i (CBS sports) is 60 fields per second, so:

1920x540x60=62,208,000 pixels per second. 540 represents the number of lines in a field versus the number of lines in a frame (1080).

The conclusion is that the total resolution for 720p video based material is not that much less than 1080i video based material. 720p video has almost as much temporal resolution as 1080i has spatial resolution. That's why ESPN has always claimed 720p is better for fast moving material like sports - no interlaced artifacts to deal with.

Another way to look at this is that if you output 720p native video material at 1080i, you are interpolating 1920 pixels from 1280, yielding artificial horizontal resolution. But, you also are converting a 1280x720 frame into a 1920x540 field, thus reducing its vertical resolution from 720 to 540 lines. Outputting 720p video material to a 1080p projector should yield 1920 pixels scaled from 1280, and 1080 lines scaled from 720. If the scaling of that material is good, this should yield the best looking 720p material.

So, if you're watching baseball or football on ESPN, the best images should be achieved by outputting at your receiver's 720p resolution and letting your projector or scaler scale both vertical and horizontal resolution up, rather than reducing the vertical resolution by outputting at 1080i.

Of course, none of these compromises has to apply to film based material, and 1920x1080 trumps 1280x720 in a perfect film world. Since most of what we watch is film based, most of the time 1080i is more appropriate for output to a 1080p projector. And since changing output resolution on a satellite receiver is usually a bit of a hassle, I don't bother with it on 720p material most of the time, either.

Correct me if I'm wrong.

Thank you for the informative reply. As you state there is a lot of confusion around the various resolutions. As I originally stated I tried both the 720p and 1080i outputs and couldn't really see a difference but its difficult to do a true comparision with the long delay in flipping back and forth.


Truth be told, you might not see any difference even if you could view them side by side. Much depends upon your seating distance and content, as I mentioned previously.


I'm still a little confused. Are you simply saying that a 1080i signal has more pixels than a 720p signal and therefore should provide a cleaner picture?

The short answer? Yes, 1080i contains twice as many pixels per frame and therefore potentially twice as much detail per frame.

Keep in mind, we're talking about HD DVD film based content which is encoded on the disc at 1080p/24.

Also keep in mind that your Pearl will take the 1080i signal and will cleanly deinterlace it to produce 1080p frames. The Pearl will not display an interlaced signal on-screen without first converting it, so for film based content, my response to your next quote (below) is moot.


I understand that the time between frames...

We're talking about the time betwen FIELDS. Not the time between FRAMES. This is a very important distinction and is critical to your understanding. Perhaps it would help if you did a search on Google for a primer on interlacing.


...is so quick that the human eye really can't decipher but in reality for that fraction of a moment isn't the 1080i signal made up of 540 lines of data while the 720p is 720 lines of data?

540 is the number of vertically counted lines in a single FIELD of a 1080i FRAME. A 1080i FRAME is composed of two FIELDS. First, the odd lines appear (the first field), and a moment later, the even lines appear (the second field). While it is true that each field contains 540 lines, it is also true that every single one of the 1080 lines in the FRAME appear on the screen for your eyes to see.



The result of interlacing is not lost spatial resolution, but rather combing artifacts resulting from the odd and even fields being separated in time. And honestly - I have never seen combing artifacts on a 1080i signal because the scanlines are so darned small. Also, remember, your Pearl will not display an interlaced signal without first deinterlacing it, and film-based HD-DVD content will deinterlace quite nicely.


Would I see a noticeable difference if I ran a VGA cable to the monitor and got native 1080p?
Doubtful. Many users have reported that they prefer the picture over component, but I cannot verify this since I have never tried VGA. Keep in mind, the Pearl's deinterlacer is giving you true 1080p when fed 1080i film based content from HD DVD.

We're talking about the time betwen FIELDS. Not the time between FRAMES. This is a very important distinction and is critical to your understanding. Perhaps it would help if you did a search on Google for a primer on interlacing.


I was semi familiar with interlacing and frames but found the following website to refresh my memory http://neuron2.net/LVG/interlacing.html. Between this and your answers I think I better understand the issue. All of my viewing via the XBOX 360 is HD DVD film based so the simple answer is to leave the output at 1080i. I am an expat based in Indonesia and I can only dream about HD television, maybe by 2010 they will have HD TV in Indonesia. For the time being I will need to be satisfied with my 1080p blueray movies on the PS3 and 1080i HD movies on my XBOX 360.

Thanks again for all the help on clearing this up for me.