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do i need a hdtv?


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9 replies to this topic

#1 of 10 OFFLINE   Kirk Pete

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Posted October 06 2003 - 02:57 PM

Do i need a hdtv to make use of a progressive scan dvd player

#2 of 10 OFFLINE   MarcianoD

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Posted October 06 2003 - 03:33 PM

I do not think so. The progressive scan converts the signal. Some HDTVs do that already so you can have progressive scan without it on the dvd.

#3 of 10 OFFLINE   Michael Reuben

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Posted October 06 2003 - 03:55 PM

[quote] The progressive scan converts the signal. Some HDTVs do that already so you can have progressive scan without it on the dvd. [quote] I'm not sure what you're trying to say here. Many HDTVs upconvert any signal they receive to 480p (or an even higher resolution). But that's a different issue.

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#4 of 10 OFFLINE   Bob McElfresh

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Posted October 07 2003 - 03:51 AM

[quote] so you can have progressive scan without it on the dvd. [quote]
All DVD's can support progressive scan - it is NOT something extra.

There IS an optional flag on the disk that a DVD player can use to say "Feed me video in progressive order" or "Feed me video in interlace order". But many older disks did not implement this flag correctly. This may be why this misunderstanding exists.

#5 of 10 OFFLINE   ChrisWiggles

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Posted October 08 2003 - 10:17 AM

Aren't progressive players just line doubling? It's 480i on the disk isn't it?

#6 of 10 OFFLINE   Bob McElfresh

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Posted October 08 2003 - 12:44 PM

[quote] Aren't progressive players just line doubling? It's 480i on the disk isn't it? [quote]
There are 2 main things that a ProgressiveScan DVD player will do that a Standard interlace player does not:

- DeInterlace: This is where the lines of video are pulled off the disk in natural/progressive order.

- 3:2 pull-down: Movies are shot with 24 frames per second. Video and television signals are shot at 30 frames per second. A DVD player will detect how many frames are in 1 second of video on the disk and perform a 'trick' called 3:2 pulldown to make a movie play correctly on your television. (See our Primer/FAQ for more detail).

Line Doubling: A DVD player normally does not do this. A HDTV will take the analog video, re-digitize it and then attempt to add rows of video so that it matches some internal format. Some HDTV's use 512, 520, 700, 720, ... etc as a internal format. Signals below this format are "line doubled" or "up converted" to the internal format. Signals like 1080i that arrive are "down converted" to the internal format. The rest of the television is optimized to handle & display this internal format.

It's actually very hard to make the internal electronics handle all 3 major formats (480, 720, 1080) WITHOUT some compromise unless they create a lot of extra electronics. By converting to some single, internal format the designers can optimize both the electronics and optics to create a rather nice picture.

There was a long thread in the "Display Devices" fourm that discussed the merits/problems of different internal formats. I think no clear conclusion emerged that any brand of HDTV did a better/worse job than any other.

#7 of 10 OFFLINE   ChrisWiggles

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Posted October 08 2003 - 02:14 PM

No wait..., taking an interlaced source and "doubling" it is deinterlacing. Beyond that you are adding more lines of video overall. Doubling interlaced video adds those lines in between the active lines (odd or even), thus not increasing resolution, but sort of "increasing" the lines during any one refresh. Right? It was my understanding that the video contained on the disc is standard NTSC 480i.

#8 of 10 OFFLINE   Bob McElfresh

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Posted October 09 2003 - 08:14 AM

The term "doubling" IS often used incorrectly. Thats why you see a lot of posts saying: 480i - 480 lines of video - Interlace (1,3,5,7,9..) 480p - 480 lines of video - progressive (1,2,3,4,5..) This is less ambigious. All current DVD's carry 480 lines stored in Mpeg2 format. NTSC .. implies an interlace display but it's NOT a format for information on a disk. (They are related - but not the same.) So strictly speaking - a DVD is not really "High Def". It does not carry any more information per frame than your local CATV/antenna feed. It CAN be progressive if you have a Progressive Scan DVD player, but this is NOT more resolution/information (although it looks a lot sharper/cleaner) Only when you get a source that outputs 720/1080 do you have more information per frame. If you look, you will start to hear about experiments with "HD-DVD" or "Blue Ray" or "Blue Laser" DVD's. These are DVD's that store 720/1080 lines per frame. But no existing DVD player could play these. It would need a whole-new player and the disks would not be backwards compatible with existing players.

#9 of 10 OFFLINE   ChrisWiggles

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Posted October 09 2003 - 08:58 AM



That makes no sense to me, if my understanding so far is correct. Progressive or not (line doubled or not), is totally unrelated to the video that is on the disc, because the disc is only 480i. Just wanna make sure I'm not bonkers. Posted Image

#10 of 10 OFFLINE   Bob McElfresh

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Posted October 09 2003 - 12:55 PM

You are not bonkers. It caused a lot of discussion around here several years ago. Is video stored in interlace or progressive order on a DVD? The answer is: each title can be different. There is a flag on the Disk that tells a player what order to pull video rows to get progressive-scan or interlace output. So the physical ordering does not matter as long as the players read the flag and follow the instructions correctly for the type of output it wants. So it's actually accurate to say that a DVD contains 480 lines of video per frame and NOT specify the order.




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