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Why laserdisc soundtracks are better…
#1
Star 
...than most of the DVD - and few BD, as I read also in some forums. I don't want to talk about MUSE laserdisc audio now, because I'm not expert in that branch, but whoever wants to talk about it, is welcome!
OK, let's start!

NTSC laserdiscs
could contain a different combination of soundtracks:
  • two mono analog
  • one stereo analog
  • two mono analog + two mono PCM
  • two mono analog + one stereo PCM
  • one stereo analog + two mono PCM
  • one stereo analog + one stereo PCM
  • AC3 + one mono analog + one stereo PCM
  • DTS + one stereo analog
I'm pretty sure there is no AC3 laserdisc with two mono digital soundtracks, as PCM is used for stereo (surround) soundtrack, and there are almost no DTS laserdisc with two mono analog soundtracks (Mortal Kombat is an exception), as analog is used for stereo (surround) soundtrack, but I'm sure there is NO laserdisc that contain both DTS and AC3 soundtracks!

Things are easier for PAL laserdiscs:
  • two mono analog (on laservision)
  • one stereo analog (on laservision)
  • two mono digital
  • one stereo digital
  • DTS (well, only one title ever released!)
The PAL laservision is practically another standard, as PAL laserdisc video could be watched on old laservision player, but digital soundtracks could not be heard! The contrary is usually not true, as the most part of the PAL laserdisc players could also play analog soundtracks. There is NO AC3 PAL laserdisc!

Now, let's take a closer look at the different soundtrack types:

ANALOG


Albeit analog soundtrack on laserdisc is the worst of the possible ones that could be found on it, the quality is pretty good - here you are some numbers:
  • Frequency response: 20-20000hz (±3dB)
  • Signal-to-noise ratio (CX off): >50dB (up to 58dB)
  • Signal-to-noise ratio (CX on): >62dB (up to 74dB)
  • Channel separation: >50dB
Not that bad, uh? Better than vynil, audio cassette, second only to VHS HiFi Stereo. It could contains also surround sound; some concerts could be found only on analog laserdiscs, as they are never released with digital audio; the most part of japanese bilingual laserdiscs have the japanese language recorded onto the analog soundtrack... why? Maybe because it sounds better? The answer is yours...

PCM (Pulse Code Modulation)

The first (and most used) digital soundtrack that appeared on the laserdisc format was PCM, stereo or dual mono, 16bit 44.1KHz 1441kbps - it has the same technical specifications and quality of the CD-audio.
  • Frequency response: 4-20000hz (±0.1dB)
  • Signal-to-noise ratio: 96dB - up to 117db (EIAJ)
  • Dynamic range: 96dB - up to 99dB (EIAJ)
  • Channel separation: 80dB - up to 90dB (EIAJ)
  • Wow & Flutter: <0.001% (EIAJ)
All the PAL laserdiscs after the end of 1980's have digital audio; NTSC continued to have both analog and digital soundtrack, as the standard allowed it; several surround types could be found on laserdisc, not only the famous Dolby Surround, but also DTS Surround and CHACE surround.

AC3 (Dolby Digital)

The first AC3 laserdisc was "Clear and Present Danger" and was released in 1995; the AC3 soundtrack is stored in the right analog channel, and is RF modulated; to be decoded, a laserdisc player with the AC3 RF output is needed, and must be connected to an RF demodulator and a Dolby Digital decoder, or to an amplifier with built-in RF demodulator and DD decoder.

The AC3 soundtrack has always the 384kbps bitrate at 48KHz, almost always 20bit 5.1 channels, but in some (rare) cases the number of channels could vary - usually during extra material like making of, documentary etc.

I found no proof (until now), but there are evidences that the theatrical mixes are used for AC3 laserdisc soundtracks "as is"; in fact, many argue that laserdisc Dolby Digital sounds better than the DVD counterpart, also if the latter has an higher bitrate; indeed, most DVD DD soundtracks are mixed taking in account home users, and they should sound good with any kind of audio configuration, and hence it's a sort of compromise, while the laserdisc has that "in your face" sound typical of theaters.

Someone could think that is not possible, as the theatrical AC3 soundtrack is 320kbps, while laserdisc has 384kbps... think that the LD AC3 is stored on analog form, and surely the signal contains some sort of stronger error correction, due to the fact that analog reading is not perfect; also, it is possible that the signal is simply padded from 320kbps to 384kbps, as it was more economic to take the theatrical mix and copy to laserdisc than remake a home version...

DTS (Digital Theater System)

The first DTS laserdisc was "Jurassic Park" and was released in 1997; DTS soundtrack takes the place of the PCM soundtrack, leaving free two analog tracks, (almost) always used for the movie soundtrack, allowing the owner of an old analog-only player, or who has not a DTS decoder, to listen to it. To be decoded, a laserdisc player with digital output is needed, and a DTS decoder, or an amplifier with built-in DTS decoder.

As the DTS soundtrack are in place of the PCM one, it has the same technical data, 16bit 44.1KHz 1441kbps but, at the contrary of the PCM two channels, it has 5.1 discrete channels.

The laserdisc DTS soundtrack IS NOT the same of the theatrical one: in fact, in theaters, DTS uses a different
codec, APT-X, encoded as ADPCM at 882kbps and recorded on CD-ROMs, with a compression of 4:1, while DTS on laserdisc uses Coherent Acoustics perceptual coding compression scheme, encoded at 20bit 44.1KHz with a bitrate of 1235kbps (incapsulated at 14bit 44.1KHz, padded to 16bit, to lower the white noise, when playing the track without a decoder, by 12dB) and a compression of 3:1. Hence, the DTS laserdiscs should be better than the theatrical DTS, as the home codec is newer and better, and bitrate higher with less compression.

As almost all DTS DVD have the so-called "half bitrate" soundtracks (754kbps padded to 768kbps) instead of full bitrate (1509kbps padded to 1536kbps), the laserdisc DTS soundtracks is always better than "half bitrate" DTS DVD; in some cases, could be preferable to full-bitrate DTS DVD due to different mixes used.

[added on 2016/11/03] According to many posts written by Disclord (R.I.P.) on LDDB forum, very often the DTS LD used a 18 bit masters, while the AC3 LD often used 16 bit masters; also, surround channels on the first year or two after the introduction of DTS laserdiscs are mixed +3dB louder.[end]

CONCLUSIONS

Using a laserdisc soundtrack for preservation purposes is often a good choice; when the DVD or BD soundtracks are of low quality, or technically inferior, or "improved";  when the DVD or BD soundtracks have different formats; when the DVD or BD have no soundtrack in a certain language; or, simply, when there are no DVD or BD of a certain title or version at all!

There is only a price to pay: capturing and converting laserdisc soundtracks is an HARD task... but really rewarding! - just finished JP2 AC3 and DTS, I know what I'm talking about... (^^,)



EDIT 2018-04-24:

Found this interesting webpage, and this paragraph in particular:

Quote:This paper presented listeners with a choice between high-rate DVD-A/SACD content, chosen by high-definition audio advocates to show off high-def's superiority, and that same content resampled on the spot down to 16-bit / 44.1kHz Compact Disc rate. The listeners were challenged to identify any difference whatsoever between the two using an ABX methodology. BAS conducted the test using high-end professional equipment in noise-isolated studio listening environments with both amateur and trained professional listeners.

In 554 trials, listeners chose correctly 49.8% of the time. In other words, they were guessing. Not one listener throughout the entire test was able to identify which was 16/44.1 and which was high rate [15], and the 16-bit signal wasn't even dithered![/url]

That's why we all love so much laserdisc PCM soundtracks...



EDIT 2018-04-27:

I think this info could be useful:

disclord Wrote:NEVER listen to a non-encoded disc with CX on - its not been properly encoded for the CX noise reduction and will not sound right.  It's not there to be used on non-CX'd discs.  However, an analog CX disc can be listened to without CX decoding - that was one of the design goals, that it not sound noticably weird when not decoded - it will just have more background/disc noise.  Every digital title that has the analog soundtrack duplicating the digital has CX - discs with commentary/bilingual/AC-3 discs do not have CX (some are improperly auto encoded with it though, sadly).  DTS discs with analog stereo tracks are all CX.  CX requires that the two encoded channels be related, i.e. stereo or mono, to decode correctly, thus incorrectly encoded commentary/bilingual are not in CX compliance.
(found here: http://forum.lddb.com/viewtopic.php?f=12&t=1148)
Fundamental collection thread | Vimeo channel | My personal blog
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#2
Mortal Kombat DTS has two analog mono tracks, as one is the commentary.

I think CD PCM came first, as the format hit the market in late 1983. AFAIK, the first digital sound LD players came out in 1984 or 1985. The earliest PCM LD title I have is from 1986.

One question I've had for a while is whether an early analog stereo PAL disc will play back in stereo on a later model player. Several years back, I spent more than a few bucks getting my hands on a rare PAL title, and getting it transferred/converted to NTSC as I don't have a PAL capable machine. Unfortunately, the soundtrack turned out to be mono, in spite of the labels on the disc and jacket as stereo.
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#3
Interesting fact about Mortal Kombat... maybe is the exception to the rule! Big Grin

PCM: AFAIR the specifications for digital audio laserdisc, or prototypes, were ready before CD-DA, but I could be wrong.
PAL digital audio: at least one model was not capable to play laservision analog tracks, maybe the CLD-315 IIRC, but probably there were others; it happened that, despite the fact cover stated stereo, the actual tracks were dual mono...
Fundamental collection thread | Vimeo channel | My personal blog
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#4
I thought that PCM tracks on LaserDiscs were 48 KHz / 1536 Kbps  Shocked   
I guess it's still better to capture them like that when you're not doing bit-perfect as it will avoid any bad upsampling.

And about the analog LD audio VS. vinyl comparison, I don't think it's fair because most of vinyl records literally blow away their CD counterparts in term of quality!
I know it's not the right topic for that but still Smile
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#5
It's debatable if the better quality could be obtained by a bit-perfect capture and resampling, or analog recording at the correct sampling rate... unless you have a laserdisc player with a very good DAC and a sound card with a very good ADC, I think the resample option is the way to go IMHO.

Vynil quality: I'm aware of it, but analog laserdisc audio could be comparable, if not better.... it will be interesting to make a comparison between a vynil LP of a concert, and its LD counterpart!
Fundamental collection thread | Vimeo channel | My personal blog
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#6
A two-stage approach (capturing at the original sample-rate and then resampling) is always better, as far as I'm concerned, because you can take advantage of improvements in resampling techniques as they arise and repeat the second stage.  If you capture at a sample-rate other than the original, the resampling is "baked in" and cannot be improved subsequently.
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#7
Interesting. Thanks for these informations! I'll try to upsample my next captures in post then Wink I'm using the excellent SoX resampler. Should be adequate.
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#8
First post edited; read the added info, it would be worthwhile!
Fundamental collection thread | Vimeo channel | My personal blog
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