Laserdisc question--white lines running through picture?? (1 Viewer)

[Steve*MH]

For all those diehards out there that still have a laserdisc player and some laserdisc. I just picked up a couple of cheap laserdisc movies at a garage sale and found that one side of one of them was infected with sporatic white lines running through the picture(almost like it needed to be tracked, but laserdisc to my knowledge cannot use tracking). I have around 30 laserdisc, and these are the only ones that have this problem for extended periods of time. Anyone else experience this? And any ideas of what can be done to improve or get rid of these lines? Could it be a "dirty" disc or one in need of a repair/cleaning kit, or just the way the disc was manufactured. Basically, is there anything I can do?? The lines truly bother me when I am used to DVD quality. Otherwise, the laserdisc quality is very close to my dvds.
Thanks.

 

[Rob Gillespie]

White lines are usually indicative of a bad pressing. Sometimes they 'roll' down the picture, other times appearing across the image. 'Laser Rot' looks different - lots of speckles all over the entire screen.

You can try cleaning the disc but there's probably nothing you can do to completely fix the problem.

 

[Gordon McMurphy]

Which disc is it - which movie?


Gordy

 

[alan halvorson]

Dirty surface or, as Rob said, a bad pressing.

For your info, laser disc players from the later part of the 80's used a tracking system similar to that of cd. Early tracking systems were rather primitive, later machines incorporated a "floating" system that performed much, much better.

 

[RobD]

A quick question to those who may know, was Tin Cup a known bad pressing?? I have it and the PQ is bad (But it's not Laser Rot), my player is a recent one.

 

[BrentPollard]

Since we have a new LD thread I have a question. I can get an old Sony MDP455 LD player very cheap. It has been modified with an AC3 out. The previous owner's receiver had a built in converter so he has no AC3 demodulator. This is no big deal as I have only 1 or 2 AC3 LD's and most likely will not buy any. So my question is can the AC3 out pass a regular signal.I have used up all the audio in's both analog and optical on my pre/pro, but I still have 2 free coax inputs. Can I hook the LD players AC3 out to a coax in and get a signal?

 

[Mick Wright]

Can I hook the LD players AC3 out to a coax in and get a signal?

Unfortunately, no.

 

[Kevin M]

Here's a question I have wanted to ask regarding LD's, how is the analog track actually recorded onto an LD? That is, how does an LD physically contain an analog stereo soundtrack and how is it read and played back, is it similar to the optical soundtracks on film prints?

 

[Seth Paxton]

Brent, as Mick said the answer is no.

And for the curious what you have to understand is that AC-3 signal is really just an unfiltered analog right signal (I think DD was packaged on the right analog, maybe left, I forget now).

What they did was modulate or piggy-back the digital bit stream onto an analog wave for storage on the analog track. That's why you need a demodulator first, to extract the digital bitstream from this analog carrier (just like over the air digital broadcasting basically).

What goes into the digital coax input is a digital bitstream, even though the connector type is the same. So you need to have that digital bitstream pulled off the AC-3 out first.


Kevin, I don't know the physical structure of the LD surface, but keep in mind that LDs have video stored in ANALOG format and I believe the analog video/audio package is stored together in regular NTSC composite format. I've never been sure how the digital (PCM) tracks were then stored with the analog signal.

Some people, not saying you, sometimes mistakingly think that LD video is digitally stored like DVDs.

 

[Kevin M]

No, I understand that it is an analog format but I was just curious as to how it works, an optical analog format is an interesting creature to me & I have owned them for nine years now.

 

[Lewis Besze]

It's FM analog.
When a DD 5.1[RF] is present,that usually occupies the left channel of the analog tracks.These tracks after digital sound[PCM] became normal on LD, was relegated to filmmakers commentary and such.

 

[Kevin M]

Frequency Modulation? As in the same FM that old FM radio uses?

I have searched for sites that go into technical detail but I haven't found any that go beyond very simplified layman's terms.

 

[Damin J Toell]

I have searched for sites that go into technical detail but I haven't found any that go beyond very simplified layman's terms.

You may find these helpful:
First, a definition of frequency modulation: http://www.chemistry.bnl.gov/gpmd/fm.html

Then, the specs of the FM signals used on LD: http://www.access-one.com/rjn/laser/legacy/ld96.html

DJ

 

[Matthew Kiernan]

Yes. TIN CUP was pressed by Sony, whose discs were notorious for succumbing to rot and quickly becoming defective. I held off that LD (as much as I loved the movie) for that very reason.

 

[Kevin M]

Thank you Damin, that second article is exactly what I was looking for.
BTW what site is that taken from, it can't be Replication News.com as the link in the article is dead.

LD may not be digital but it is certainly a primitive ancestor/forerunner to the basic principle of CD & DVD digital optical containment in that it recognizes the modulation of the FM signal in the "Pits & Lands" on the aluminum surface. Wild.

 

[Joel Fontenot]

Kevin, the main page that second link was from is at
http://www.access-one.com/rjn/laser/laserdisc.html

Joel

 

[Rachael B]

Kevin, actually LD preceeds CD. CD was extracted from LD. I think PCM was actually invented by Denon, but it was headed for LD. I'm not sure if LD or CD actually got PCM first. Sony didn't think that LD was going to pay off fast and took their LD technology to Phillps and they came up with the CD format. LD was first market tested in Atlanta in 1978. It was here in Knoxville soon thereafter. Phillips had several plants here. offices and even product testing. Actually, I once applied to Magna-Box as a technical writer. Dhey seid I shout'a gradiated en Anglish stead uf buzibizness.

I was chating with a guy who did torture tests to LD's and CD's one night at a party. They baked them, frooze them, threw them, put acid on them, in brine, antifreez and many other substances. Damn, sounds like a fun job. It's got that Mr. Science element. I knew about the oxidizing glue (holding CD's and LD's two halves) from that night on. I'd been considering an LD player and that little chat helped me to decide yes and get on with it. I knew which audio and video discs to avoid too!

So, really LD and CD are double stars that revolve around each other, CD's just orbit faster. Best wishes!

 

[Kevin M]

Thanks Joel.

Any other LD sites that anyone can think of? I found one last year that was shockingly comprehensive but I can't seem to locate it again.
Actually, now that I think about it, I believe it covered every Home Video device ever concocted.

Kevin, actually LD preceeds CD. CD was extracted from LD.

I'm sorry but where in my post did you get the impression that I thought CD came first?

 

[Lewis Besze]

PCM was implemented on CD first.

 

[Joel Fontenot]

Regardless of who thought who said what about when...PCM made it to LD sometime around 1986.

http://www.oz.net/blam/LaserDisc/FAQ/ is a good site. It's based on the original Laserdisc FAQ at http://www.cs.tut.fi/~leopold/Ld/FAQ/index.html but that one is no longer maintained.

And, then there is the site about how it all began - MCA's DiscoVision, at http://www.oz.net/~blam1/DiscoVision/index.htm


Joel

Edited to correct the last link.