[newman]

Hello,


A couple of days ago I was playing a LD and every time there was a silent scene, followed by a dialogue/sound, I could hear a (lover volume) copy of the sound that would have been played a moment later.

Kind of a "reverse echo" as if the audiotrack was taken, shifted a fraction of second forward with a lower volume and fused with the correct audio.


I had completely forgotten that effect that was so common with tape based recording systems (VHS-Compact Cassette), but that LD has turned on my curiosity; so can anyone please give me a technical explanation of this phenomenon?


And is there a way to "cure" it?


Thanks.

 

[John F. Palacio]

Good one!


In analog tape this was known as "print-through" and it is caused by the adjacent layer magnetizing the one with print-through. It actually prints-through to both the one before and the one after but is more apparent in the most silent one.


In records(vinyl) it was known as "pre-echo" and it is cause by actual deformation of one groove by an adjacent one.


Other than this being in the master tape that was used to cut the LD, I have no idea how this could happen on an LD. But would like to learn.

 

[Reznor007]

It might have something to do with the source, your specific player, or possibly the fact that LD is an analog format, not digital like CD or DVD.

 

[cpc]

It might have been there on the original analog master tape and the soundtrack was copied as is to the LD. Certainly a LD can't be responsible for that type of effect, I don't think anyways

 

[newman]

Thanks to all!


Obviously the problem with the LD audio was from the master tape

Anyway the reply of Mr. Palacio solved the mistery to me:

Quote:

Originally posted by John F. Palacio In analog tape this was known as "print-through" and it is caused by the adjacent layer magnetizing the one with print-through. It actually prints-through to both the one before and the one after but is more apparent in the most silent one.

So the problem arises during storage...

Am I right if I say that the time lapse between the audio and the "print-through" changes during the playback (since the tape is winded on a bigger or smaller spool)?

 

[John F. Palacio]




Yes the problem arises during storage. As far as different timing depending on where it occurs in the reel, you are probably correct. I have not done any actual measurements, though or heard of somebody who has

 

[Tuomy]

I vaguely remember recording engineers storing master audio tapes "tails out", that is wound backwards on the reel, so that the lead-in print-through would be at the smallest diameter point on the reel. You understand I was very young at the time (yeah, right.) At ( I think) 15 inches per second, that would put the printed "pre-echo" so close to the start of the tune that you couldn't really hear it...I think....it's been a long time...

jmt

 

[bluedevils]

Tuomy and Palacio are completely correct. This means that the source material for your LD was at some point, analog. You don't hear the words tails out as much now with prominence of the digital medium.