Over the years I've seen a lot of confusion in the submit/updates I receive for all kind of titles and maybe it's time to sit down and give the whole picture once and for all. I'll explain things the way I got to understand them over the years, if I made some mistakes, they will hopefully be corrected by more knowledgeable visitors.

I will try to keep the inner technological bits hidden and provide only what someone considering buying or selling a LD, or upgrading a Player or A/V Amp, should consider to avoid confusion and, perhaps, ending with something different than expected. After reading this, you should be able to know what kind of soundtracks are on a specific LD just by looking at the cover and/or the disc labels.

As a base for understanding, standard Laserdiscs can really only have 3 variants: ANALOG, DIGITAL, ANALOG+DIGITAL.

I will use this box for each example:

Analog Left =	or or something else
Analog Right =	or or something else
Digital Left =	or or something else
Digital Right =	or or something else

ANALOG MONO

At first, the commercial releases for Home Video were under the DiscoVision product name. They started in 1978 with JAWS in NTSC, analog mono sound and CAV mode only.

Analog Left = Analog Right =
Digital Left =
Digital Right =

The LD had actually 2 analog tracks: Left and Right, but since they were both identical (Right track is the very same as Left track), I just display Analog Tracks as the only option. You could choose to listen to Left or Right separately if your player allows it, but it would sound exactly the same. This is equivalent in quality to your FM Radio and it was quite enough for the end of the 70's!

	Analog Tracks

When you submit a new title or an update for this type of soundtrack, use SOUND = ANALOG, LEFT = MONO and leave RIGHT empty since it's the same soundtrack.

ANALOG STEREO

Analog Left + Analog Right =	STEREO
Digital Left =
Digital Right =

With stereo TV sets and home HiFi audio systems, it was time to release some titles in glorious stereo sound. Apart from a few demo discs, the earliest commercial release on Stereo DiscoVision I could find is:

	Analog Tracks

When you submit a new title or an update for this type of soundtrack, use SOUND = ANALOG, LEFT = STEREO and leave RIGHT empty since it's the same stereo soundtrack.

CX ENCODING

Analog Left + Analog Right =	CX-ENCODED STEREO
Digital Left =
Digital Right =

For more details on CBS CX technology, I can refer you to the Wikipedia page. But for LaserDisc practical purpose, it means that an analog stereo soundtrack could be "eXpanded" (as in "increased dynamics") as well has reduce interferences between the video and audio signals if encoded on the disc with CX and then decoded in the Player the opposite way. For Players that didn't include the CX decoding chip, Pioneer released the stand-alone Pioneer Laser Vision CX Noise Reduction Unit R-1000.

Look for the CX logo somewhere on the back of the cover or on the disc labels. MONO soundtrack can also be CX-encoded but this brings little difference to the final result. CX is designed to work on STEREO materials. The opposite is also true, if you do not have a STEREO or MONO sountrack but have different soundtracks on Left and Right stracks (for example a bilingual release), then CX encoding cannot be used.

	Sound Encoding	Analog Tracks

When you submit a new title or an update for this type of soundtrack, use SOUND = ANALOG-CX, LEFT = STEREO and leave RIGHT empty since it's the same stereo soundtrack.

MULTI-AUDIO

Analog Left =	(different from Analog Right)
Analog Right =	(different from Analog Left)
Digital Left =	or or something else
Digital Right =	or or something else

Multi-Audio in a Analog universe can only mean that the Left and Right tracks are different. This also means that CX encoding is not possible. Players will allow you to select left or right channel separately. Playing a release with multi audio without selecting a track first will sound very weird since two completely different soundtracks are being played at the same time!

Criterion was quick to see potential for additional contents and since King Kong was a mono sountrack, why not put it on the left track and use the right track for something completely different: a running commentary!

	Sound Encoding	Analog Left	Analog Right
			Commentary

Another neat usage is to have one language on one track, and a different language on the other one (here: English and Japanese)

	Sound Encoding	Analog Tracks
		Bilingual

When you submit a new title or an update for this type of soundtrack, make sure to NOT select a -CX choice, and set LEFT and RIGHT to their specific contents, or LEFT to Bilingual only.

With the arrival of Philips/SONY Compact Disc, all the rage was around Digital Audio and LaserVision (previously DiscoVision, rebranded when Pioneer took things over) wanted to ride that wave too.

LaserVision + Compact Disc = LaserDisc. Simple.

But that would be too easy. Some Analog/Analog-CX releases are carrying the LaserDisc Logo when they have no Digital tracks and in Europe they went the opposite direction marketting-wise and called them CD Video. Instead of putting the Disc in Laser, they put the Video in CD! To make it even more confusing, some "CD Video" were actually of CD size (5"/12cm) and carrying both CD tracks and LD video. What a mess for consumers.

Here I need to split the story in two because NTSC and PAL got different fates.

ANALOG(-CX)+DIGITAL Analog Left = Analog Right = Digital Left = Digital Right = Basically there was enough bandwidth left on NTSC Laserdiscs to add a PCM Digital Audio stereo signal while retaining the analog stereo tracks. Again, if your Player was a little old but had the correct output connector, it was possible to extract the Digital Audio tracks using stand-alone device Pioneer Laservision Digital Sound Processor DA-1 and then... output it on analog stereo plugs again! No Toslink or Coax output yet. For the Analog Tracks, everything explained in the ANALOG section above still appplies, including the CX encoding. For the Digital Tracks, we now have 1 more pair of mono tracks to play with. Most of the time the Digital and Analog tracks will carry the same soundtrack like most music releases (live concert or music videos).  Sound Encoding   Digital Tracks   Analog Tracks    But how about offering the mono original movie soundtrack in Digital and offer a split between mono soundtrack and mono score on Analog?  Sound Encoding   Digital Tracks   Analog Left   Analog Right    Musical Score Simply offer bilingual mono sound in both Digital and Analog.  Sound Encoding   Digital Tracks   Analog Tracks      Bilingual   Bilingual Or push the bar higher with 3 different languagues: French and English on Digital mono with Japanese on Analog stereo.  Sound Encoding   Digital Tracks   Analog Tracks      Bilingual Technically it could have been possible to have 4 different mono tracks on a single disc, but I have never seen an example of such oddity.

DIGITAL Analog Left = Analog Right = Digital Left = Digital Right = PAL video was already using more bandwidth than NTSC by design and when it was time to add Digital Audio, both analog and digital couldn't be combined. It would have to be one of the two flavors, but not both at the same time.  Sound Encoding   Digital Tracks  There were a lot less possible combinations (basically the same as Analog, but Digital only), but we could still have bilingual releases:  Sound Encoding   Digital Tracks      Bilingual It also works for split mono/score or mono/commentary but there were so few of them in PAL Digital Audio format that I didn't initially write the code to separate Digital Left from Digital Right (except for bilingual). The split was also a welcome feature for Karaoke titles to have one track with lead singing and one track with music only for practice.

MATRIXED SURROUND

Now that we have Stereo, there are interesting things that can be done! For example, we can add additional audio channels (center and rear) encoded into the stereo tracks. This type of surround sound went through many names and branding over the years, but it can usually be found as "Dolby Stereo" (for theaters), "Dolby Surround" (for home video), "Dolby Pro-Logic" (the decoding of Dolby Surround) and also got variants from competing companies such as "DTS Stereo" (DTS), "Ultra Stereo" (USL), "Chace Stereo" (Chace Productions, to turn mono into stereo surround), "RSS (Roland Sound System)".

Look for specific logos somewhere on the back of the cover or on the disc labels. Sometimes it also shows as an opening logo sequence when playing the disc itself.

	Sound Encoding	Analog Tracks

	Sound Encoding	Digital Tracks

	Sound Encoding	Digital Tracks	Analog Tracks

	Sound Encoding	Digital Tracks	Analog Tracks

	Sound Encoding	Digital Tracks	Analog Tracks
		Recorded in	Recorded in

	Sound Encoding	Digital Tracks	Analog Tracks

When you submit a new title or an update for this type of soundtrack, choose the appropriate SOUND = ANALOG and/or DIGITAL w/ or w/o CX, LEFT = [choose the right Surround flavor] and leave RIGHT empty since it's the same stereo soundtrack. For some reason, RSS doesn't seem to be compatible with CX for games, maybe because there is some real-time encoding happening and adding CX would add too much processing power?

REALTIME SPACIALIZATION

For a handful of videogame titles, ROLAND RSS system was used to provide stereo spacialization (sound location) to extend the playing experience. I don't have a lot of details on how it was stored/used on a LD-ROM, if you have any technical informations, I'm interested!

	Sound Encoding	Digital Tracks	Analog Tracks

DOLBY DIGITAL/AC3 (5.1)

Analog Left =	MONO ONLY
Analog Right =	DOLBY DIGITAL AC3RF
Digital Left =
Digital Right =

Now, with the improvement of technology and home theaters getting more and more electronics (DSP, etc.) it was time to stop ADDING extra info in existing tracks but a good time to REPLACE one track with something more fun. Since the Analog tracks were separate analog signals, it was possible to encode (modulate) a digital stream inside the analog bandwidth. The choice was made to use the Analog Right track and to put a modulated version of a digital 5.1 soundtrack at 386kbps.

When played on old players it would sound like garbage on the analog right track (possibly damaging your speakers, be careful!) but more recent players would automatically mute the right analog track and provide an AC3RF output for external decoding from AC3RF to AC3. For more details on AC3RF, please read the dedicated HELP SECTION here. If you've been reading this whole page, then you already know that CX Encoding will not be possible since the 2 Analog Tracks are completely different.

It's a clever trick because you keep maximum backward compatibility for most player owners and remain true to the LaserDisc specs:

• Old system with analog only will play the soundtrack mono (unless it's been replaced with a commentary, Criterion used this on more than half of their AC3 releases).
• Standard Dolby Pro-Logic systems will keep using the Digital Audio Surround soundtrack.
• Whoever upgraded to AC3RF decoding (via demodulator or integrated A/V Amp) will enjoy the 5.1 soundtrack

	Sound Encoding	Digital Tracks	Analog Left	Analog Right

	Sound Encoding	Digital Tracks	Analog Left	Analog Right
			Commentary

Towards the end of the LaserDisc era, Dolby was trying to cram even more information into the 5.1 channels and... used the old matrix surround trick from Dolby Surround to encode an additional 6th channel in the 5.1 stream thus creating a 6.1 Surround EXtended experience. The 6.1 bit is not set on LD so you'll have to force your Amp into 6.1 mode to enjoy the extra track.

	Sound Encoding	Digital Tracks	Analog Left	Analog Right

Although it could have been possible to release a PAL release with AC3 (going back to Analog only, left mono, right AC3RF), it would have made little sense because these disc would mainly become AC3-only, no other Surround tracks and entry level PAL players would stop playing analog audio altogether. Making it a nearly impossible-to-sale product. As a matter of fact, there were 3 Dolby Digital titles released in Europe but ... NTSC!

	Sound Encoding	Digital Tracks	Analog Left	Analog Right

	Sound Encoding	Digital Tracks	Analog Left	Analog Right

	Sound Encoding	Digital Tracks	Analog Left	Analog Right

These are respectively the last USA and Japan AC3 releases:

	Sound Encoding	Digital Tracks	Analog Left	Analog Right

	Sound Encoding	Digital Tracks	Analog Left	Analog Right

DTS Digital Surround (5.1)

Analog Left =
Analog Right =
Digital Left + Digital Right =	DTS 5.1

Now comes DTS who helped Steven Spielberg create the Jurassic Park sound experience (George Lucas was supporting Dolby instead) and they wanted to find a way to turn it into a commercial product. DTS in theaters are separate CD-ROMs with time synchronization on the movie reels (because there was no more space on the reel after adding Dolby, SDDS and the stereo tracks!). But for commercial release it would have to be turned into a constant bitrate and 386kbps of Dolby Digital was not enough. They chose to replace the Digital Tracks this time around, using both tracks for additional space at a bitrate of 1,235kbps since this approach had already been taken to produce DTS CDs. But at least this time no dedicated RF out plug and a need for an extra demodulator, a simple toslink/coax output would be enough.

This decision had the consequence that a DTS LaserDisc cannot have LD-G captioning (the data sync is burried in the digital audio).

Jurassic Park was re-released in DTS on LD (and would eventually also get an AC3 release).

	Sound Encoding	Digital Tracks	Analog Tracks

	Sound Encoding	Digital Tracks	Analog Tracks

	Sound Encoding	Digital Tracks	Analog Left	Analog Right

Of course the Analog tracks could still be used for commentaries, and they were, sometimes even for 2 different commentary tracks, or commentary and isolated musical score:

	Sound Encoding	Digital Tracks	Analog Left	Analog Right
			Commentary	Commentary

	Sound Encoding	Digital Tracks	Analog Left	Analog Right
			Commentary	Musical Score

Technically PAL LDs could this time carry a DTS soundtrack (and ONLY a DTS soundtrack) consuming both Digital Tracks for it. In reality, only one release ever took advantage of this feature:

Analog Left =
Analog Right =
Digital Left + Digital Right =	DTS 5.1

	Sound Encoding	Digital Tracks

These are respectively the last USA and Japan DTS releases, there were no DTS ES 6.1 releases on LaserDisc:

	Sound Encoding	Digital Tracks	Analog Tracks

	Sound Encoding	Digital Tracks	Analog Tracks