Jaws LD mono track

[pipefan413]

found the LD audio was too quiet. the dvd mono sounded  much more aggressive.

I agree, but I fear that's probably only because of noise reduction on the DVD and later releases. The DVD is also missing some stuff, as crissrudd4554 noted. The only thing missing from the LD as far as I can see/hear is that wee "yeah" when they haul the empty cage out of the water, but nobody's lips appear to be moving and they've already seen the cage by this point so it strikes me as weird anyway.

Can't stop noticing that phantom beach burp now if I watch anything other than the LD version...

[pipefan413]

I watched this the other night and yeah, I agree that the DVD audio sounds more punchy but the LD is arguably a truer representation of the theatrical mono imo (and that wee "yeah" that it's missing just seems weird to me) so that was my choice for watching the full film.

I have a question about it though:

This is a LD-sourced "mono" track, but has 2 channels. I had assumed that it was simply just the same channel duplicated into each... but it's not. I split the PCM into two separate .wav files for the L and R channels and the two files contain different data. Does anybody know why that would be the case?

My AVR was able to use DTS Neural:X to identify it as mono nonetheless in order to pipe the whole thing through my centre speaker (which is actually surprisingly capable of significant low-end grunt, it turns out!) but I find this curious because it differs from other LD mono tracks I've got in my collection. If I pick Dolby Surround mode instead, it ends up mostly coming out of the centre but the decoder tries to chuck all the low end to the L and R speakers instead, which I guess makes sense for most setups but in my case the low end is actually better on my centre speaker.

EDIT: Holy crap, I just realised I already asked this in the same thread and forgot. I didn't even think to scroll up because I have zero recollection of having asked. Only noticed when I went to shut the page. What a plonker. Sorry! But yeah, if anybody knows, please do tell.

[allldu]

This is a LD-sourced "mono" track, but has 2 channels. I had assumed that it was simply just the same channel duplicated into each... but it's not. I split the PCM into two separate .wav files for the L and R channels and the two files contain different data. Does anybody know why that would be the case?

Are you sure about this? I don't see any differences between two channels on the LD audio.

[pipefan413]

This is a LD-sourced "mono" track, but has 2 channels. I had assumed that it was simply just the same channel duplicated into each... but it's not. I split the PCM into two separate .wav files for the L and R channels and the two files contain different data. Does anybody know why that would be the case?

Are you sure about this? I don't see any differences between two channels on the LD audio.

Yeah, 100%. If you split the channels then look at the data, they don't match. This is the case for both the 44.1 kHz and 48 kHz versions of the file. Either look at them in a hex editor or do a binary comparison with something that generates checksums e.g. HJ-Split.

They look almost indistinguishable if you're just looking at waveforms but they're not the same data. Here's the zoomed-in waveform of the first non-zero data in the bitstream of the 44.1 kHz "mono" track:



In other words, either this may not be a bit-perfect digital rip as I thought it was, or it is but the digital track on the LaserDisc itself doesn't have two identical channels. I don't think it's an analogue capture, unless whoever captured it cleaned it up afterwards (because I don't hear any clicks/pops or see them in the waveforms).

DISCLAIMER: I've never ripped a LaserDisc because I don't have any LD gear whatsoever, but I'm just working with what I've seen elsewhere. Other mono rips, such as the ones floating around for Halloween and The Terminator, seem to have started off as 2.0 "dual mono" but have then had 1 channel either folded into the other or discarded to turn them into 1.0 before being made available. I'm interested to know if they were also like this in the first place and, if so, whether half the data was discarded or folded down into 1 channel. (I know there is also a 2.0 dual mono track on The Terminator but I think that one does have two bit-identical tracks; I'm ripping it off a disc ISO right now to check. EDIT: Nope, The Terminator is the same! The 2.0 version off the Team Blu disc has slightly different data in the L and R channels, like Jaws does here. But the LD audio I have for Halloween is only 1.0.)

Well that's interesting... I wonder what's actually different about the two channels, and why there is any difference at all? I presume the same was quite likely true of Halloween as well, so I wonder if that one had one channel discarded, or if it was folded down to 1.0 from the original 2.0?

[bronan]

The dual mono tracks on LD usually aren't exactly identical. Not sure what kind of equipment they were using to transfer from the original optical mono track but there are definitely minor analog fluctuations. I can't speak for others but I usually just drop one of them and just sync one channel since its faster, then you can always dupe it back to dual mono later.

[pipefan413]

The dual mono tracks on LD usually aren't exactly identical. Not sure what kind of equipment they were using to transfer from the original optical mono track but there are definitely minor analog fluctuations. I can't speak for others but I usually just drop one of them and just sync one channel since its faster, then you can always dupe it back to dual mono later.

Indeed you can. I suspect that may be exactly what happened with the Criterion Halloween track, since I've only ever seen it as 1.0. Thanks!

[zoidberg]

Laserdisc is a stereo format (both its digital and analogue tracks). Therefore mono is presented as 'dual mono' for compatibility. As to both tracks being bit-identical, tiny variances shouldn't make a difference to playback through pro-logic so long as they remain in phase.

[pipefan413]

Laserdisc is a stereo format (both its digital and analogue tracks). Therefore mono is presented as 'dual mono' for compatibility. As to both tracks being bit-identical, tiny variances shouldn't make a difference to playback through pro-logic so long as they remain in phase.

Yeah, I suspected as much. And I don't expect the differences to make a difference to playback - and in fact I've verified that it doesn't in the case of Jaws and Back to the Future, for example - but I found it curious that there was any difference in the first place. I presumed that most LD mono tracks would have been recorded from mono magnetic masters and it seems redundant to record them twice rather than just record a single 1.0 track and duplicate it for compatibility, but it seems like the tracks have actually been recorded twice hence the very small variances; clearly you'll get tiny variations if you record the same thing twice using anything analogue in the chain.

Thanks guys, sorry if this is really dumb thing to have asked. As much as I wish I did, I don't have any LaserDisc stuff kicking about.

[allldu]

Wasn't Back to The Future released in Stereo originally?

[pipefan413]

Wasn't Back to The Future released in Stereo originally?

Oh aye it was, sorry, I'm muddled because I'm forum-ing when I should probably be focusing on work. Ahem.