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Discussion Starter · #1 ·
I was intrigued after getting an external video processor and talking to the tech that revealed that blu-ray wasn't really 1080p but 1080i/60 that is deinterlaced/upconverted in the player itself.


Therefore UNLESS you're playing back a 1080/24p movie to your 1080p monitor, connecting the blu-ray to a "HIGHER quality" VP as 1080i and letting the VP do the de-interlacing would be BETTER than having the player de-interlace (similar to connecting your SD DVD player to your VP as 480i instead of 480p).


on Wiki, the tech specs reveal this.

Resolution Frame rate Aspect ratio

1920x1080 59.94-i, 50-i 16:9

1920x1080 24-p, 23.976-p 16:9


most newer BR players will output 1080p/24 to most modern LCD/plasmas that will display as 1080p/24fps. But I have an older BR player that cannot output 1080p/24. The LCD is a 1080p panel.


Does that mean my player is deinterlacing/upconverting to 1080p?
 

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Quote:
Originally Posted by poopiehead /forum/post/15544825


I was intrigued after getting an external video processor and talking to the tech that revealed that blu-ray wasn't really 1080p but 1080i/60 that is deinterlaced/upconverted in the player itself.

No, it's natively 1080p, and Blu-ray players can output and process a 1080p stream as it is encoded on the disc. The video encodes must include timings for 1080i60 as part of its specifications, but they can be ignored and the player can access and process the 1080p content directly. The output of the video decoder of a Blu-ray player is 1080p, not 1080i.


Note that, HD DVD required deinterlacing 1080i60 to 1080p60, even though content was stored on the disc as 1080p24. The output of the video decoders were 1080i only. This is actually why the A2 and A3 were 1080i only, and you've never seen a Blu-ray player that is limited to 1080i. The A20 and A30 had a deinterlacing chip in them, and would deinterlace 1080i to 1080p before output--the same as what your TV or an external video processor does. (Yes, the A30 and A20 were more or less a way to scam an additional $100 out of consumers who didn't know any better.)


Eventually, Toshiba figured out how to extract the 1080p24 signals as well. Originally, this wasn't going to be possible, just as, originally, it wasn't going to be possible to transmit HD audio bitstreams with HD DVD. Aall audio from an HD DVD authored in advanced mode--all commercially released titles--must pass through the mixer, meaning that bitstreaming wasn't supposed to be possible. Toshiba engineers figured out a way around that as well.


Toward the end of the format, they might have figured out (I can't remember) how to extract the 1080p24 signal and do 3:2 pulldown on it (so no deinterlacing occurs), but that functionality would have been limited to the XA2 and A35, because all the other players that supported 1080p output were configured as I mentioned above--deinterlacing chip separate from the rest of the circuitry. I'm not sure how they managed to modify the output of the video decoders, but that's what they did, apparently.

Quote:
on Wiki, the tech specs reveal this.

Resolution Frame rate Aspect ratio

1920x1080 59.94-i, 50-i 16:9

1920x1080 24-p, 23.976-p 16:9

Yes, what this means is that Blu-ray supports two 1920x1080 timings: 50/60i and 24p. When you set your player to 1080p without 24fps on, what is output by a player after 3:2 pulldown is 1080p60, and this is what a 60 Hz TV displays. Blu-ray cannot store material in that format natively. It's limited to either 1080p24 or 1080i60.


It is the case that when connected to a TV that does not accept 1080p24 signals, the video from Blu-ray must be processed to 1080p60 via 3:2 pulldown or deinterlacing.

Quote:
Does that mean my player is deinterlacing/upconverting to 1080p?

For film material, the short answer is no, for all the reasons above. For video material, which is actually stored on the disc as 1080i60, yes.
 

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Discussion Starter · #3 ·
thank you for a VERY detailed answer. it's starting to make sense.


so to be 100% clear...if your blu-ray output or TV does not work with 1080p24, then there is some deinterlacing and 3:2 pulldown happening....so you should always use the best VP you have...be it the player to make it 1080p60 or output as 1080i60 and let the video processor (external or the one in the TV) do the 3:2 pull down / deinterlacing.
 

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IMO, convert 1080p24 to 1080i60 via 3:2 pull down does not require any fancy hardware. First it doesn't need to de-interlacing. It's quite easy to deal with because the raw video stream is already 1080p24 (unlike DVD in which you have to put in 480i video stream).


The only time you need de-interlacing is 1080i60 video (documentary and concert videos). In this case, since you're not really dealing with 3:2 pulldowned 24p source, de-interlacing is quite easy as well.


So, purchasing an external VP just for BD is just wasting your money, IMHO.


Now, de-interlacing and upcoverting SD DVD using external VP is another story altogether.
 

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Discussion Starter · #5 ·

Quote:
Originally Posted by Foxbat121 /forum/post/15546678


IMO, convert 1080p24 to 1080i60 via 3:2 pull down does not require any fancy hardware. First it doesn't need to de-interlacing. It's quite easy to deal with because the raw video stream is already 1080p24 (unlike DVD in which you have to put in 480i video stream).


The only time you need de-interlacing is 1080i60 video (documentary and concert videos). In this case, since you're not really dealing with 3:2 pulldowned 24p source, de-interlacing is quite easy as well.


So, purchasing an external VP just for BD is just wasting your money, IMHO.


Now, de-interlacing and upcoverting SD DVD using external VP is another story altogether.

awesome...that's probably why there was no degradation from connecting my Blu-ray to the VP. I got the VP for cable TV, my appleTV and for my DVD player.


my blu-ray is the older Panasonic BD10a so no 1080p24 output but without any degradation in the 1080p60 processing, I know I can confidently look at the next step in my home theatre and get that CIH set up (VP is for the needed vertical scaling)
 

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Quote:
Originally Posted by poopiehead /forum/post/15546241


thank you for a VERY detailed answer. it's starting to make sense.


so to be 100% clear...if your blu-ray output or TV does not work with 1080p24, then there is some deinterlacing and 3:2 pulldown happening....so you should always use the best VP you have...be it the player to make it 1080p60 or output as 1080i60 and let the video processor (external or the one in the TV) do the 3:2 pull down / deinterlacing.

Here's how 3:2 pulldown works. It should be more properly called 2:3 pulldown, as that's what really happens, but anyway...


So you take 4 progressive frames, A B C D. You repeat them in a 2,3 fashion:

A, A, B, B, B, B, C, C, D, D, D


That's it. When you have a 24Hz progressive image to begin with, there's nothing to detect, and nothing fancy that needs to be done. In other words, 2:3 pulldown when you start with 1080p24 is impossible to mess up. Every video processor should process this exactly the same.


Now, when you start with an interlaced image, it's much more difficult, because you don't actually know what the original framerate was before the video was interlaced. Video processors detect it by examining the frames themselves, and that can take time (the best processors lock onto the right cadence. Furthermore, there's a variety of cadences: 2:3 (film), 2:2 (video), 2:3:3:2 (some DV cams), 8:7 and 6:4 (some anime, for 8 fps and 15 fps content respectively), and still others. Detecting the wrong cadence gives you jaggies (because the deinterlacer is putting the wrong frames together).


Really, the quality of the video processor only comes into play when you're deinterlacing or scaling an image. You should see the same image quality when you output 1080p60 from a BD player as when you output 1080p24 and send to an external processor that takes the video to 1080p60.
 

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What a great thread!! I hope someone will shed some light into some of my questions.

I have a 720p native display that can display at 720p/24Hz and can also accept a 1080p/24. I also have a VP that will accept 1080i/60 but not 1080p.

I can connect a BD player to the display in basically 3 ways:

a)- Straight player to display and let the display downscale 1080p/24 to 720p/24. How would this down scaling normally be done? Is there much room for the display to mess up? The result is outstanding BUT I have noticed some artifacts depending on the disk that I play.

b)- Player to display and let the BD player down convert 1080p/24 to 720p/60. How is this normally done? Is there much room for the player to mess up? The resulting PQ is great, may be not as smooth in certain slow pans BUT w/o artifacts.

c- Player to VP at 1080i/60 and VP to display at 720p/60. Here, if I see it right, the player will have to interlace the 1080p signal from the BD to 1080i and then do the 24 to 60 thing and send it to the VP. Right? Are there good chances to mess up here?

Then , the VP will have to deinterlace and downscale? Or may do downscale and then deinterlace? and then send the 720p/60 to the display. Right. I guess this is what a good VP is made for, right?

Even if the VP is excellent, this seems to be a lot more convoluted way to displaying the BD signal than the previous a) and/or b) solutions. Right? The results are also very good BUT they appear to be missing that resolution/fullness/richness I think to observe in a)/b). I am not very good at judging this things.

What would be the best theoretical way to go?
 

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Quote:
Originally Posted by FGM /forum/post/15555752


a)- Straight player to display and let the display downscale 1080p/24 to 720p/24. How would this down scaling normally be done? Is there much room for the display to mess up? The result is outstanding BUT I have noticed some artifacts depending on the disk that I play.

I would guess it would just do a straight downscale, similar to how a scaling chip takes 480p to 1080p. I haven't got any familiarity with devices that accept 720p24 signals, so I really don't know.


Whenever you scale video, you need to resample. There can't be a 1:1 correspondence between a 720p and 1080p image. There's 2.25 pixels in a 1080p image for every one in a 720p image, so you can't even associate blocks together (and honestly, that would be the worst way to scale possible).


Instead, you need to resample the image. There's many ways to do this: linear (bad), billinear (better), nearest neighbor (ok), cubic (very good), bicubic (really good), etc. What algorithm is chosen depends on the power of the processing chip. I'd guess that downscaling is usually done pretty well (better than upscaling, on average), but I'm quite certain that some chips are better than others.


I can't speak for results myself. While I have a 720p setup myself, I haven't tested much gear, and nothing side by side. There's also practically nothing written on 1080p -> 720p conversions. No one seems to be interested much at all; there's far too much obsession over 1080p.

Quote:
b)- Player to display and let the BD player down convert 1080p/24 to 720p/60. How is this normally done? Is there much room for the player to mess up? The resulting PQ is great, may be not as smooth in certain slow pans BUT w/o artifacts.

There's two ways: 2:3 pulldown on the 1080p24 to make 1080p60, and then downscale from there, or downscale to 720p24 and then 2:3 pulldown to make 720p60. The first is far less efficient, as you need to scale 60 frames instead of 24, and you end up repeating something you already did 36 times, which is pretty dumb.


I don't know how chips do it. I'd like to imagine they're smart enough to scale to 720p24 first, since then they can use their processing power on better scaling algorithms rather than doing the same thing a bunch of times.

Quote:
c- Player to VP at 1080i/60 and VP to display at 720p/60. Here, if I see it right, the player will have to interlace the 1080p signal from the BD to 1080i and then do the 24 to 60 thing and send it to the VP. Right? Are there good chances to mess up here?

This is by far the worst option. Deinterlacing is far more difficult than downscaling, as it requires detecting the right cadence and then reconstructing progressive frames from the interlaced ones using that. There's plenty of chance for error in here.

Quote:
Then , the VP will have to deinterlace and downscale? Or may do downscale and then deinterlace?

There's a way to go from 1080i to 720p directly without technically deinterlacing or scaling. The way to do it kinda combines both, looking at even and odd fields to construct a 720 line image from two 540 ones.


Quote:
The results are also very good BUT they appear to be missing that resolution/fullness/richness I think to observe in a)/b). I am not very good at judging this things.

You can always lose resolution when you downscale or deinterlace. Really poor deinterlacers essentially throw away half the frames (basically, they scale the interlaced image), which means the resultant image has double the lines of the old one but the overall image is only half the resolution. To test for this, send an interlaced image of alternating lines. (i.e., make field 1, which has only even lines all white, and make field 2, which has only odd lines, all grey.) If the deinterlacer isn't throwing away half the fields, the result will be an image whose lines alternate between grey and white. If it is throwing away the odd fields, the screen will be all white.


When you downscale, you lose resolution by not making use of as much information as you have. In other words, your resampling algorithm doesn't use as many neighboring pixels as it could. I can't really comment on how often this happens. I really don't know. There's just nothing written on it.
 

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Princess Aurora,

Thank you for your thorough and honest reply; I have found it to be very informative.
 
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