8mm Forum: Laserdisc audio

»	8mm Forum » 8mm Forum » Laserdisc audio

UBBFriend: Email this page to someone!

Author

Topic: Laserdisc audio

Mike Blasko
Junior
Posts: 19
From: Cleveland, OH, USA
Registered: Apr 2017

posted June 29, 2017 07:41 PM

Historical curiousity: many members claim that they have re-recorded audio on a Super 8 feature via a laserdisc. DVD and other 24/25 FPS sources I fully understand. Sync box, pulse from audio/computer, all make sense.

From a laserdisc, this just doesn't make sense unless it was 25fps? As an experiment, I've tried just about everything from an NTSC (29.97) disk to get a sync to a film print. No dice. I can only assume this was a Pedro type box started at the same time at 25fps on a PAL frame disk?

Very curious to any one who has done this - I don't see how without distortion or serious editing in a non-linear editor this could work. There are some mixes on laser that are unique, so I don't consider the format for audio completely dead..

| IP: Logged

Barry Attwood
Phenomenal Film Handler

Posts: 1411
From: Enfield, U.K.
Registered: Aug 2003

posted June 30, 2017 04:24 AM

Mike,

It definitely was done here in the U.K. by Keith Wilton, John Clancy and David Locke, I'm not sure what system they used to sync up a GS 1200, but I've had prints re-recorded from Laserdisc (I had a print of "Terminator 2" done this way, superb quality sound), so I know it was done, most probably using a sync box and running the GS in sync at 25 fps.

| IP: Logged

Winbert Hutahaean
Film God

Posts: 5468
From: Nouméa, New Caledonia
Registered: Jun 2003

posted June 30, 2017 04:39 AM

Aren't Laser Discs in the UK using PAL hence 24/25 fps?

--------------------
Winbert

| IP: Logged

Brian Fretwell
Phenomenal Film Handler

Posts: 1785
From: London, UK
Registered: Jun 2014

posted June 30, 2017 06:29 AM

They would be 605/50 interlaced and if composite video in PAL, I imagine, as they were at the time of VHS and all masters would have been made that way. Also that is what UK TVs at the time could display.

| IP: Logged

Bill Brandenstein
Phenomenal Film Handler

Posts: 1632
From: California
Registered: Aug 2007

posted June 30, 2017 08:33 PM

Mike, I think you're barking up the correct tree(s) here. Issues at hand:
- is the film cut the same as the video cut
- is the film mastering at 25fps, and if so, was it linearly sped up so it corrects itself if done at 24?
- is the LaserDisc PAL or NTSC, and if PAL, how is the frame rate conversion handled as regards the sound?

The Pedro boxes could lock to a 25fps video signal with no problems. But he couldn't make it do the same trick for NTSC, which technically runs at 23.976. To make matters worse, if you're doing digital out from LD, it's at 44.1KHz sample rate, which works out to the uneven 1839.337500002 samples per film frame (as opposed to 2002 samples per frame at 48KHz). If you're digitizing from the LD's analog outputs, then your device should be clocked to the video out (hard to do) so that it doesn't drift.

In other words, there's a LOT to go wrong. I've done it from NTSC LD with perfect results, so we can say with certainty that it's possible.

| IP: Logged

Mike Blasko
Junior
Posts: 19
From: Cleveland, OH, USA
Registered: Apr 2017

posted July 15, 2017 08:26 PM

Thanks everyone for the helpful info. I believe the biggest thing is that I didn't put together the 44.1/48k frame length difference as mentioned by Bill.

I believe that and the analog motor drift without video sync led to the Demise.

Interestingly, Adobe audition had a feature that did line it all back up, but with terrible pitch distortion. Seems like an easier trick in the U.K.

Thank goodness for 24fps/48k blu-ray!

Mike

| IP: Logged

Bill Brandenstein
Phenomenal Film Handler

Posts: 1632
From: California
Registered: Aug 2007

posted July 17, 2017 05:43 PM

Indeed! Thanks for reporting back, Mike.

| IP: Logged

All times are Central

Printer-friendly view of this topic

UBB.classic^TM 6.3.1.2