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Discussion Starter · #1 ·
I hear some folks suggesting we should add some DScaler type deinterlacing to one of the software players.


OTOH, I hear other folks extolling the virtues of displaying DVD on Radeon cards in a 1080i resolution.


I don't have my Radeon card yet so I can't try this. But 1080i is an interlaced resolution. It would seem that if the individual fields were being scaled properly there would be very little point in deinterlacing anything, just to display it interlaced at 1080i.


Am I missing something here? Could someone who uses 1080i for displaying DVD's please watch some video sourced DVD and post the results?


For instance the Video Montage sample off Video Essentials is an excellently mastered mix of film & video.


I'm just wondering if the added resolution makes up for the interlace, especially on RPTV's that might otherwise be limited to 544p.


- Tom
 

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Hmm,


I have not tried any video based DVDs on my HTPC...


But for film based ones, I think Radeon in 1080i mode de-interlaces, then scales, and then re-interlaces.


All I know for sure is that it looks darn good. And I don't think scaling while the pictire is interlaced would work well at all...


Bert
 

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Tom,


I'm pretty sure that when running the Radeon at 1080i the interlacing is done at the hardware level and is completely transparent to the Windows software, which as far as it knows is running at 1080p. I also agree that scaling an interlaced image from 720x480 to 1920x1080 would probably not work very well.
 

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Discussion Starter · #4 ·
Quote:
I'm pretty sure that when running the Radeon at 1080i the interlacing is done at the hardware level and is completely transparent to the Windows software, which as far as it knows is running at 1080p. I also agree that scaling an interlaced image from 720x480 to 1920x1080 would probably not work very well.
I'm not sure that's what I was saying. I actually wonder if one or more of the DVD players is smart enough to know that it is handling an interlaced output and, if so, not bother to do pulldown removal or deinterlace. That is, just send the fields to the (720x240) overlay buffer 1/2 frame at a time, telling DirectX that it is and can be displayed interlaced. The individual overlay frames would be scale to full width, half height, and offset by 1 line when displayed at 60 hz.


It seems completely contrary to what we do in DScaler but for a 1080i display it actually may be the best. (or not?)


But I haven't seen it yet myself and once I do see it I still won't know for sure what they are doing.


But I was hoping someone would watch some video source this way and tell me if it looks good. I've been very curious why some Radeon users seem to like 1080i so I figured there must be some reason for it.


- Tom
 

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Quote:
Originally posted by trbarry
I hear some folks suggesting we should add some DScaler type deinterlacing to one of the software players.


OTOH, I hear other folks extolling the virtues of displaying DVD on Radeon cards in a 1080i resolution.
For me, not having a Radeon means no 1080i output. No matter how good it may or may not look, the point is moot. OTOH adding improved deinterlacing to a software player means better progressive playback from all video cards. That would be very, very nice! :cool:


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Firstly - how can my Radeon which I use send out VGA 1080I???


Anything above 800x600 makes my Sony go crazy???


Also - I am very lost obviously - but isnt the 720P the all encompassing desired resolution for DVD?
 

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Mikecazz-


You have to use the VGA ouput of your video card to your TV, either by using a VGA cable, VGA-5BNC, or VGA to component (transcoder). You'll have to use Powerstrip to force timings and resolutions that HDTV's accept.


trbarry-


Those of use that can't currently run 1080i (or any interlaced resolution for that matter) with our Radeons (if you're running on Win2K) are stuck with progressive modes (540p). 3-2 pulldown detection de-interlacing would be great for films with poor flags. Right now, that's all the software DVD players depend on. If the flags aren't set correctly, which is the case for allot of popular discs, then it has to resort to some sort of video de-interlacing method (bob/weave, or adaptive).


If the image is to be scaled, you're first going to either need both corrosponding fields of information, or interpolate the missing field. Sometimes the image on the DVD is stored as a 720x480 progressive frame; sometimes it's stored as two 720x240 fields, leaving the 3-2 pulldown conversion up to the MPEG decoder; and sometimes the 3-2 pulldown is allready applied and stored (redundant fields) on the disc, as 720x240 fileds.

If the flags are set correctly, the software can pull the single 720x480 frame out, and scale it to whatever you specify. If not, then the software either bobs or weaves fields to create a full frame, which isn't the best. Adaptive de-interlacing provides a little better result, but it can still cause unwanted artifacts.

If players could lock onto the 3-2 cadence, you could still find the matching field, even if the flags were set incorrectly, providing a better image.

Once the image is scaled, say to 1920x1080 (for 1920x1080i output) from the 720x480 frame, then the software must apply 3-2 pulldown in real time, sending out 1920x540 fields to the overlay.

Basically, you get better scaling results if you start with a complete image.


-Ryan Dinan
 

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Earlier someone mentioned that in order to display DVDs at 1080i, the Radeon deinterlaces, then scales, then reinterlaces, and asked if that was a waste.


Well, I think that's actually the only correct way to go from 480i to 1080i, and here's why. For simplicity's sake, I'm going to show the conversion from 480i to 960i, not 1080i, because that's just a simple line doubling.


Let X be the lines from the first field, and Y be the lines from the second field. Then 480i starts out like this:
X.X.X.X.X.X.X.X.

.Y.Y.Y.Y.Y.Y.Y.Y

deinterlacing 480i to 480p produces
XYXYXYXYXYXYXYXY

which is then scaled by interpolation to 960p,
XXYYXXYYXXYYXXYYXXYYXXYYXXYYXXYY

(of course, you're not just going copy the lines twice, you're going to interpolate). Finally, the result is re-interlaced:
X.Y.X.Y.X.Y.X.Y.X.Y.X.Y.X.Y.X.Y.

.X.Y.X.Y.X.Y.X.Y.X.Y.X.Y.X.Y.X.Y

Now if I tried to go from 240i to 960i simply by scaling each field separately, I'd get this:
X.X.X.X.X.X.X.X.X.X.X.X.X.X.X.

.Y.Y.Y.Y.Y.Y.Y.Y.Y.Y.Y.Y.Y.Y.Y

So you see? The result isn't the same. Obviously things for 1080i would be similar, just without the nice clean multiple of 2.


This suggests to me that 1080i, while it may indeed look slightly better than 540p, will nevertheless suffer from deinterlacing artifacts.
 

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Discussion Starter · #9 ·
Quote:
Once the image is scaled, say to 1920x1080 (for 1920x1080i output) from the 720x480 frame, then the software must apply 3-2 pulldown in real time, sending out 1920x540 fields to the overlay.

Basically, you get better scaling results if you start with a complete image.
Dunno. I suspect that's not completely how I'd do it.


But if you knew it was going to go to a 1080i display at 60 hz anyway, then maybe some of the other stuff is sort of an unneeded ritual. The real point would be to make 60 interlaced fields that could use hardware scaling to look good on the standard 1080i RPTV.


And I'm still not completely convinced that process needs either deinterlacing or IVTC but maybe it is still better to create 480 line progressive frames before scaling.


I realize that not everyone has a Radeon card. I don't myself yet but the one I ordered was only about $60. And of course many people aren't optimizing for a 60 hz 1080i RPTV either, but that's what I happen to be using now.


I think it is still an interesting question. Maybe I'll just have to wait a few days and try it.


You could maybe even make a case for a DScaler RPTV option to process differently for 1080i output but I'm not sure yet what that would entail. Maybe I'm just off on a snipe hunt.


- Tom


Oops - notice cross post with above.
 

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Tom,


I run my 1271Q at 1280i x 960i through a Radeon LE and it looks better than it did at 1164P x 852P. I will be looking at a DVD with mixed film and video tonight and will check out the video performance.


Jack
 

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Discussion Starter · #11 ·
Quote:
Now if I tried to go from 240i to 960i simply by scaling each field separately, I'd get this:


X.X.X.X.X.X.X.X.X.X.X.X.X.X.X.

.Y.Y.Y.Y.Y.Y.Y.Y.Y.Y.Y.Y.Y.Y.Y


So you see? The result isn't the same. Obviously things for 1080i would be similar, just without the nice clean multiple of 2.


This suggests to me that 1080i, while it may indeed look slightly better than 540p, will nevertheless suffer from deinterlacing artifacts.
Michael -


Yeah. Between the top post and yours I took the dog out for a long walk and went through a similar line of reasoning. You may well be correct but I'm still not completely convince for some reason that I wouldn't do things differently for interlaced output.


But I can't explain why yet, so maybe there is no good reason.


- Tom


PS - (OT) It's kind of neat that if you hit preview before submitting now you can see crossed posts now before you are committed. We didn't used to be able to do that.
 

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Discussion Starter · #12 ·
Quote:
I run my 1271Q at 1280i x 960i through a Radeon LE and it looks better than it did at 1164P x 852P. I will be looking at a DVD with mixed film and video tonight and will check out the video performance.
Jack -


Thanks, yeah, that's what I was looking for. :)


- Tom
 

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This may be slightly off-topic, but I believe the question of why to use 1080i has come up. First, I should mention that most RPTV users such as myself who talk about DVD playback at 1080i are probably using a custom resolution to reduce overscan. In my case, I play DVD's at 1704x960i, which produces zero overscan.


On my system, DVD playback at 960i looks noticeably better than 540p-derived resolutions. Not only are there far fewer jaggies and scaling artifacts, there is also better peceived resolution. In addition to judging based on actual movie playback, I used the resolution test pattern in AVIA to compare 960x540p, 920x518p, 1920x1080i, and 1704x960i. On my system, 960i provided the most resolution with the least amount of scaling artifacts (1920x1080i running second - this makes me think that the fact 960 is an even multiple of 480 is an advantage).


There are some downsides to interlaced resolutions, though. First, the hardware support in the Radeon has some bugs that cause the cursor overlays used for DVD menus to be messed up in interlaced resolutions. This makes keyboard/remote navigation of DVD menus pretty much impossible. My work around for this is to start the DVD software in a 540p resolution, and then switch to 960i once the movie has started playing (I can easily switch back and forth with Pronto/Girder macros).


Second, there's another problem in that when the overlay surface gets created it is progressive instead of interlaced, meaning you get a double-height image of the top half of the actual image. This fix for this is to use the powerstrip hotkey to 'refresh custom timing'.


Somewhat related to the above, if you try to use the 'Auto Select Bob/Weave' option in players, the overlay will get messed up at chapter breaks and you have to contantly refresh the timing. Because of this, you're going to want to use Force Weave or Force Bob depending on the DVD you're watching.


Finally, interlaced overlay works in the Win9x driver version 7093, but it does not work under the newer drivers, and it does not work under any of the Win2K drivers. Hopefully ATI will fix this in the future, but I'm not holding my breath. In the meantime, 7093 is the recommended driver to use if you want interlacing.


The list of cons may sound pretty significant, but the issues above can be worked around by using the correct drivers and a few Girder macros. IMHO the improvement in picture quality is enough to be worth the trouble. I would definitely suggest that anybody with an RPTV give 1704x960i a try.


I haven't done much testing with video-based DVD's because my collection consists almost entirely of hollywood movies. But I'll take a look at a concert video tonight and see what I can find out.
 

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Quote:
I run my 1271Q at 1280i x 960i through a Radeon LE and it looks better than it did at 1164P x 852P. I will be looking at a DVD with mixed film and video tonight and will check out the video performance.
A small nitpick here, but the 'i' or 'p' only goes with the vertical resolution, not the horizontal. So your two choices are 1280 x 960i or 1164 x 852p. Horizontal resolution is never interlaced, so there's no need to specify it.
 

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Quote:
Originally posted by trbarry
But if you knew it was going to go to a 1080i display at 60 hz anyway, then maybe some of the other stuff is sort of an unneeded ritual. The real point would be to make 60 interlaced fields that could use hardware scaling to look good on the standard 1080i RPTV.
Hi Tom,


I don't pay much attention to the HTPC forum these day but your idea always sounds interesting.


I've a Japanese DVHS deck which can record 480i analog video via composite/S-video and convert/store on a S-VHS tape in digital format (DVHS STD mode). The point is when the tape is playbacked, the deck can up-convert the 480i digital to a 1080i component output in YPbPr. The deck can't do these up-convert in real time so it's basicly useless unless you first record the DVD on a tape before playback. It does work well by recording many good old laserdiscs to tape first!


Anyway, I mean I see the point of up-convert/scaling to a higher interlace output such as 1080i.


In my test, anamorphic 1080i in 16x9 looks excellent but for fullscreen 4:3 content, 1080i is not enough as in vertical motion, there are only 540 line so the scan line struction is still visible.


Custom resolution is not a problem on a PC display card such as the Radeon (I've one). I'm actually thinking how about a even higher interlace resolution such as 2160i? 1920x2160i scanning frequency is equal to 1080p at 67Khz which many high-end CRT projectors can handle the signal without problem. At 2160i, we will have 1080p scan line in vertical panning so the scan line effect should be completely solved.


Just a though.


regards,


Li On
 
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