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Laser disc quality (and a technical discussion of NTSC video resolution) (1 Viewer)

Christopher_J_F

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Has anyone noticed how almost EVERY LD thread will turn into a discussion about Star Wars or Indy?
Common Guys! There are SOOOOOOO many movies out there not on DVD, and lots of LD that are better than their dvd counterpart.(Heavily covered in other threads.)

I get the feeling a lot of LD players will show up on ebay when SW comes out on DVD...not mine though!

On LD's, I credit most of the differences in picture quality to the care given to the transfer. I own LD's that are R-A-Z-O-R sharp, and some (although very few) that look like a second generation vhs copy. I don't blame the format for either extreme.
 

Morgan Holly

Agent
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May 12, 1999
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Thus if you have a DVD encoded for 4:3 aspect ratio, you take the 720 horizontal pixels encoded on the DVD and devide it by (4:3).
TV pixels are not square as they are on a computer, this is why 720 circles look oval on a computer but correct on a TV, not because 180 lines are thrown away. For example: if I create a 720X486 image with alternating black and white verticle lines then record it to D1 and display it on a professional TV I will see ALL 720 B&W lines in underscan, not 540. So your math still makes no sense to me.
 

Bjoern Roy

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Jerry,
425i or 425p? Major difference.
As others have pointed out, these numbers represent horizontal resolution and thus there is no 'i' or 'p'.
But even if these WERE vertical resolution, 425i and 425p would not be a 'major difference' as you put it.
Like laserdiscs, DVDs are 480i also. When a progressive player outputs 480p, all it does is reconstruct full film frames with inverse 3:2 pulldown (either by using the supplied progressive flags (which someone are 'wrong'), or actual cadence detection). The fact that the DVD player does this internally (and not externally like a scaler), only saves D/A, A/D steps (if you don't use a digital interface like SDI), but doesn't make the signal inherently progressive.
Laserdiscs for that matter are also 480i and can be perfectly reconstructed to the 24fps 480p frames they originated from, just like DVDs. Only that a laserdisc path inherently doesn't offer the ability to skip the A/D stage.
All,
the real question in comparing DVD and laserdisc thus lies in:
a) the actual stored frequency response. The fact that all these sources can be reconstructed to 480p doesn't mean they all have the same amount of detail. The frequency response is a function that varies from film to film, from scene to scene, etc. In general, even non-anamorphic DVDs store a higher frequency response in the luma channel (for chroma the difference is even greater, see b).
With anamorph DVDs, the difference is even bigger, of course. At least the 'potential' is there. Having more pixels to store information doesn't necessarily mean the frequency repsonse is actually higher. This is also basically always misunderstood in regard to NTSC vs PAL.
b) chroma bandwidth/resolution. DVD has much higher and inherently cleaner chroma resolution, since its YUV 4:2:0 and not Composite. Even the best comp filters used on Laserdisc pale in comparison to the chroma performance of DVD.
c) noise and especially chroma noise. While this can be greatly optimized by using the japanese high end players (S9, X9, X0), even those coupled with the best comp filters will yield noise floors that are considerably worse than even modest DVD setups and magnitudes worse than highend DVD setups.
d) compression artefacts. Laserdiscs usually don't have any, if they aren't derived from a previously digial compressed source. Depending on the quality of your DVD setup, compression artefacts can be anything from a slightly oddity up to a major annoyance. The latter only on really badly mastered DVDs coupled with bad decoders.
e) noise reduction. A problem with both DVDs and laserdiscs. Even the advanced noise reduction circuits in the japanese highend players can and do produce absolutely horrible artefacts.
On DVD, this is only a problem when the DVD is already mastered with too much DVNR, because then you can't defeat it. I consider it bad advice to use ANY form of DNR in a DVD chain. Related features on DVD players are only there to disable them ;)
And even some of the bad DVDs, DNVR wise, have moderate artefacts compared to the DNR circuits that are basically needed to get the high noise floor on laserdisc down to acceptable levels.
Overall, i see it like this:
- On a normal setup (TV or RPTV) with a normal DVD player and a standard laserdisc player, DVD is of MUCH higher performance. Thats because standard DVD player are of rather high quality (except probably the newest 80$ crop), while there are huge differences in laserdisc players.
- On a mid-class setup (better RPTV), with a normal-good DVD player and a jap. highend laserdisc player (S9-X0), laserdisc comes close to average DVDs in some aspects, but thats because the display isn't revealing enough to show the differences.
- On a highend FP system (e.g. 8" or 9" LC CRT) with ALL the gizmos (scalers, S9-X0, DVD through SDI), thus displaying all sources the best way possible, the difference is again HUGE. The best laserdiscs are just about watchable IMHO. For all others, i only appreciate the possibility to be able to see movies not available in HD or DVD, but the picture is just a blurry noisy mess. If i sit in my second row (thus 2.5 instead of 1.5 times screen width), it gets more accepTable.
Your milage may vary, but thats the way i experienced it over the years and i have seen and owned more equipment than most here, from midclass up to cost-no-object.
Regards
Bjoern
 

Bjoern Roy

Second Unit
Joined
Oct 15, 1998
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315
Morgan,

TV pixels are not square as they are on a computer...
Noone said they are, and this is irrelevant here.

And thats the point. The DVD could have 10.000 pixels horizontally and only 480 vertically, the circle rule to determine TVL would still apply.

The idea is NOT to measure all the pixels that you can display IN ONE LINE. But to measure only the fraction of the pixels 'in that line' that fit into the same width as the frame is HIGH.

So with a source that is correctly framed at 4:3, the TVL would always be 3/4s of the horizontal resolution, no matter if its 640 square pixels, or 10.000 super elongated ones.

Regards
Bjoern
 

DaViD Boulet

Senior HTF Member
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Bjoern,
Always a pleasure to read your informative and well-versed views! As usual, you contribute new and useful knowledge to just about everyone :)
I have a question:
DVDs are 480i also. When a progressive player outputs 480p, all it does is reconstruct full film frames with inverse 3:2 pulldown. The fact that the DVD player does this internally (and not externally like a scaler), only saves D/A, A/D steps (if you don't use a digital interface like SDI), but doesn't make the signal inherently progressive.
Perhaps it is a semantic debate about what makes a "real" 480P vs 480I format, but the fact that DVDs can have their fields "flagged" as true pairs enabling a properly coded DVD to produce a 480P image during MPEG decompression --by the few DVD players who use flag-based progressive-scan processing--has always given me reason enough to consider it a dual 480 I/P format. After all, how the video pixels are stored on the disc isn't really the issue so much as what those pixels represent. If no vertical filtering was applied to reduce aliasing for interlaced displays (a practice that takes place during mastering and shouldn't be considered an part of the DVD format's design per-se), what's to make a properly flagged film-based DVD not to be considered a 480 "progressive" format?
True, most MPEG decoders are designed to apply 3-2 pulldown to 24 frame per second (or 48 field per second if that sounds more comfortable) video data during decompression (and progressive-scan players using these MPEG decoder then use cadence detection, as you say, to reverse 3-2 and reconstruct 480P). However, there *are* MPEG decoders that are designed decode 24 fps material directly to 480P based on flag-information. Excepting the obvious occasional error in field-frame flagging during mastering, doesn't this describe a format that is dual 480I/P capable?
BTW, not trying to imply that the flag-based approach to 480P output is necessarily better or makes any difference in PQ...in fact, due to the possibility of improper flagging I tend to prefer the method of cadence-detection/3-2 reversal after MPEG comrpession as the best means to produce 480P output. My only point is that one shouldn't use this model of progressive-scan processing to indicate (or illustrate) the interlaced/progressive nature of the DVD format itself.
-dave :)
 

Damin J Toell

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After all, how the video pixels are stored on the disc isn't really the issue so much as what those pixels represent.
"Talking about ["480p"] without explaining the actual reality to those who want to debate its actual digital nature is like people who hear about "pan and scan" but then never learn about open-matting."
("Anamorphic" replaced with "480p") :)
Of course we should not call the DVD format 480p, just like you think we shouldn't use the term "anamorphic" for 16x9-enhanced transfers, because that's not its "actual digital nature." The DVD signal, no matter what the flags are, is not inherently progressive. How the pixels are stored is really the issue, just like the "actual digital nature" of 16x9-enhanced transfers is really the issue for you.
I couldn't resist. :)
DJ
 

DaViD Boulet

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Hey DJ,
yes...there definitely is a thread to my posts as of late :)
Of course we should not call the DVD format 480p, just like you think we shouldn't use the term "anamorphic" for 16x9-enhanced transfers, because that's not its "actual digital nature." The DVD signal, no matter what the flags are, is not inherently progressive. How the pixels are stored is really the issue, just like the "actual digital nature" of 16x9-enhanced transfers is really the issue for you.
I couldn't resist.
Acutally...to keep it all consistent...my point is just that DVD can be considered to encoded *both* a 4x3 *and* a 16x9 picture...so should it be considered to be able to encode *both* an interlaced *and* a progressive-signal.
There are flags on the DVD that mark a particular video stream as either 4x3 or 16x9 encoded. There are also flags that mark video as "video fields" or "progressive frame field-pairs".
My thought is that it's not fair to call DVD inherently "interlaced" just like it's not fair to call it inherently "4x3".
dave :)
 

Chad R

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Chad Rouch


Yes, the american version is pan & scan, don't know how easy it is to obtain since it's long out of print, you'd have to give eBay a shot.

There is a widescreen copy from Japan (similarly out of print) but I've never seen it, and sure it goes for a bit more on eBay.

Great flick.
 

Declan

Second Unit
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Aug 22, 2002
Messages
410
Somebody on HTF offered me the Widescreen Jap LD (sorry i cant remember who it was, appologies), but the cost of it was around $170 or so (again cant remember the exact price but it was near that ballpark)
 

GregK

Screenwriter
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My thought is that it's not fair to call DVD inherently "interlaced" just like it's not fair to call it inherently "4x3".
True, but let's call "an ace an ace" as almost all current DVDs are inherently interlaced at this time. Bjoern Roy covers rest of the DVD "480i" explanation quite well, and it should be noted that NTSC guru and ISF founder Joe Kane also goes out of his way to differentiate between 480i mastered DVDs (almost all of them) and the (rare) 480p mastered discs.
 

Damin J Toell

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My thought is that it's not fair to call DVD inherently "interlaced" just like it's not fair to call it inherently "4x3".
They're not the same thing. While the latter one is false (inherently 4x3), the former one is true (inherently interlaced). No matter what the player does to the signal, the video is inherently interlaced. Just like you believe that "anamorphic" doesn't properly describe how the data is encoded on the disc, "progressive" doesn't either.

DJ
 

DaViD Boulet

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True, but let's call "an ace an ace" as almost all current DVDs are inherently interlaced at this time. Bjoern Roy covers rest of the DVD "480i" explanation quite well, and it should be noted that NTSC guru and ISF founder Joe Kane also goes out of his way to differentiate between 480i mastered DVDs (almost all of them) and the (rare) 480p mastered discs.
I'm just trying to view this as objectively as possible. Firstly, regardless of how the data is "packed" on the disc is not the issue...it's what the data *represents* that is the issue. So I'm still trying to understand how if field-pairs are flagged on a DVD as "progressive frames" to enable an MPEG decoder to output a complete and accurate 480P image, how this somehow describes an inherently interlaced disc?
Besides, my point is that DVD as a *medium* is not limited to or inherently interlaced. If a DVD can be coded or flagged to be progressive...then the DVD medium can represent both interlaced *and* progressive video.
Yes, the the video data is "packed" or stored on the DVD as a series of "fields" rather than frames. However, this *still* does not indicate that the DVD format is inherently interlaced. Why? It's a digital format and the information on it *represents* a signal that can be both interlaced *or* progressive, regardless of the manner in which the data is physically stored. Before you brush this statement aside, consider this:
Even many (most?) "progressive-scan" digital tapes used in the studios and broadcasting stations *still* pack/store the data as "field pairs" (interlaced) on the tape because the recording archictecture was designed around an interlaced model and the most cost effective way to encode progressive-scan using that hardware convention but to flag the data so that it appropriately represents a progressive signal upon playback. Well...we still can say those tapes contain a "progressive" signal because it's flagged correctly and will play that signal back to us in progressive-scan.
With that in mind, if someone would like to try to convince me that DVDs are inherently interlaced, please particularly address the following concern:
if a DVD is flagged so that the field-data on the disc is marked as a "frame pair" to represent the complete frame data, and an MPEG decoder can be designed to produce a true 480P image from this information, how is this not a "progressive" encoding?
How is this any different than any of the other dozens of digital video formats that *also* pack data as fields to follow hardware convention but that we don't have a problem calling "progressive" because the information *represents* a progressive-scan signal?
Again, I'll agree here that for the full progressive-scan *potential* to be realized, that it would be necessary for the studios not to apply pre-filtering to reduce vertical-domain information.
Which reminds me, if you haven't already signed the HD-DVD petition which addresses that very issue with our future HD-DVD format, please do so :)
p.s. I'm not sure what Joe Kane is addressing in those comments you mention...can you point me to a source to read? Almost all film-based DVDs are properly flagged to have their field-pairs matched as progressive "frames" by all the industry comments I've read (including a discussion I had with Craig Eggers of Toshiba). It's the odd exception which flagged improperly (Ironically, "Titatic", which supposedly had no additional vertical filtering applied, is a text-book example of an improperly flagged DVD).
 

GregK

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p.s. I'm not sure what Joe Kane is addressing in those comments you mention...can you point me to a source to read?
Joe Kane discusses true 480p encoded discs when talking about his upcoming test DVD "Digital video Essentials" (or something like that, I know the disc's name has changed at least once) I would check some recent WSR articles by him on this topic. Joe plans to offer the first true 480p encoded discs, so it should be interesting.

I hope this helps, and that my explanations are now a little clearer and hopeflully all "error free". If not, someone will chime in.
 

DaViD Boulet

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Greg,
thanks for your thoughtful and informed comments!
No 3-2 pulldown has been applied!!!! said:
The only difference would be the fact that the filtering would unnecessarily reduce fidelity for those viewing in 1080P (which I personally feel is a very important issue and one that we videophiles should make sure the studios do *our* way to achieve maxiumum image fidelity on future 1080P displays). However...other than that...there's really no digital difference between the 1080I and 1080P signals if they are encoded from film-source material, and as long as the HD-DVD *format* allows for 24 fps 1080 coding with flags to designate true film pairs, I'd put forth that it too should be considered a "progressve enabled" format even if poor matering (ie, filtering) don't take advantage of the full image quality potential for progressive-scan viewers. I consider this to be a comparison between two 1080 signals...one filtered and one not...not a comparison between a native 1080I signal and a native 1080P signal, however that's my point of view and I can certainly respect someone else looking at the same scenario with a different perspective.
Bottom line is that if the debate about the "progressive" nature of DVD probably rests most meaningfully in the fact that filtering is applied at the studio to compensate for interlacing artifacts on NTSC displays. Since the DVD format was not conceived with 480P output as an initial goal (like DTS wasn't considered either), players were never designed to apply this type of filtering at the playback side so studios continue to apply it for us.
I do think there's room for debate here...and it's a important issue for another reason...the same picture quality limitation (of pre-filtering) will be a part of the HD-DVD format if we don't make sure the studios and the DVD consortium plan ahead for 1080P output so that downfiltering can be incorprated in the spec for playback hardware freeing the disc produces to provide unfiltered 1080 masters as soon as they'd like.
-dave
 

GregK

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Hi David,

I see where you're going, and with me not using direct MPEG-2 encoding (yet) in my job, my research on MPEG-2 encoding is far from complete, so both of us may be trying to "fill in the gaps" so to speak, on information we are not 100% sure on. I have some differing points on the "48 frame" DVD frame rate you hinted at, so with the disclaimers now aside, let dive back in! :wink:

(Yes...Artisan has released some DVDs from film-based content from composite NTSC masters that were literally compressed and dumped on DVD with 3-2 applied in the 60 Hz 480I format and they look pretty bad!).
Was "Jason & the Argonaunts" an Artisan title? I rented it once and can't remember at this time. If so, I think (and if a HTF member can help confirm or correct me on any this info, that would be great!) ..that J&A was from a composite transfer as you had also mentioned. But I think J&A was encoded with the MPEG-2 bitstream set to "video" and not as "film". Why do I think that? Because when I pause the disc, it only showed an interpolated field, not a true frame. So if someone knows what the the MPEG-2 flag reading is on this disc, I could find out out if my theory is correct.
 

DaViD Boulet

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Now we're having fun :)
Good points Greg, but here are some more thoughts to consider:
Again Joe Kane is trumpeting his upcoming DVD as the 1st progressive scan disc, although there already are a few obscure 30fps shot nature DVDs claiming to be the "1st progressive scan encoded" DVDs. (These should ALL be unfiltered in theory, but still may have to be um.. "tweaked" to ensure proper playback in interlaced as well.) I'm sure Joe Kane could give a better answer on this than both of us.
Sounds like Joe is talking about the first progressive-scan DVD encoded with 30 frame-per-second live-camera video. I think in that respect he's true.
BTW, I'm not making it the fact that most film-based DVDs released by major studios are encoded as 24 fps (48 fields) video streams with all the 3-2 pulldown processing being applied by the DVD player during MPEG decompression. That's a known fact (and exactly consistent with what Craig Eggers from Toshiba told me when they were first producing DVDs back in '97). I believe Jim Taylor's FAQ talks about it but if you'd like I can try to do some research and post some links.
dave :)
 

Mattias_ka

Supporting Actor
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May 21, 2001
Messages
567
I use two Pioneer HLD-X9 with a Barco 801 and I get superb picture from the good LD's and too say that they are "just about watchable" is kind of strange to me. For example, good LD's of newer movies WILL look better than many older movies on DVD, are the DVD's not "watchable"??
I'm in this for the MOVIES, not for the 1% perfect picture/sound.
 

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