Question: LaserDisc Dolby Surround Extraction

[EmpireStrikesBack198]

Hi,

I've been searching these boards for answers about ripping Dolby Surround audio from LaserDiscs, but I ended up becoming more confused, which is I'm creating another post on this topic.

From what I gather, Dolby Surround is 4.0 (left, center, right, rear) and that while a LD is analog, the audio is digital. My question: Is there a way to rip only the audio from a LD to get the separate audio channels (left, center, right, and/or rear)?

Thank you in advance for any input.

[NJRoadfan]

You can record the digital audio tracks using a sound card with SPDIF coax or optical input. Dolby Surround, and its extension, Pro Logic is matrixed surround audio recorded onto stereo audio tracks. Its decoded by a stereo receiver to recover the rear and center channels.

http://en.wikipedia.org/wiki/Dolby_Pro_Logic

[EmpireStrikesBack198]

So, that method combines the 4 channels into a single stereo track? Is there any way to get only the center channel, for example?

[Cornucopia]

Never in complete isolation.

Btw, LDs mostly had analog stereo tracks. Only very late in its lifespan did LD allow Digital stereo lpcm tracks, and only then on players that supported it.

Whether analog or digital, the signal will be captured with a cap card in realtime - no ripping possible.

Scott

[jman98]

You cannot rip ANYTHING from LD. Period. I know that people use the word "rip" to mean almost anything, but specifically it refers to copying a CD, DVD or BD disc (and decrypting if necessary) to a computer hard disc via putting the disc in the computer's CD/DVD/BD drive. Since there is no LD drive on a PC, you cannot "rip" an LD.

Hauppauge makes a few high end cards and capture devices that are also capable of capturing multichannel LD audio via an optical cable. Once you have the audio captured you can separate it into channels using various audio editing tools and do what you want with it. I'm not saying it will be easy, but it is possible. And those who told you to use audio cards for this are right that if your LD player has an optical audio out and your audio card has an optical audio input, you can go that way too, but you can't get individual channels any way you do the capture.

Scott - With all due respect, I do believe you may be confusing some things. I think that digital stereo was around from the beginning (in LaserVision the audio was always analog and some, not necessarily you, confuse that format with Laserdisc) but it did not have to be used. I've still got a lot of laserdiscs and I don't feel like going through a bunch of them, but I really do not offhand recall having many that did not have digital stereo audio. Now AC3 and DTS did get added very late in the game to LD. However I cannot find hard evidence to dispute your claim nor can I find any that points to a specific date as when digital stereo was "added" to the format. The best I can say for sure is "That's not how I remember it, but I can neither conclusively refute what you said nor conclusively prove what I said."

[NJRoadfan]

PCM audio was introduced to the format by Pioneer in 1985. Many titles were re-released with digital tracks to take advantage of the improvement. Analog audio on LD wasn't all that great although CX audio encoding helped with the noise.

Dolby Digital was the latecomer to the format. Pioneer wedged it in by encoding the AC3 data as an RF carrier stored on the right analog channel.

[jman98]

PCM audio was introduced to the format by Pioneer in 1985. Many titles were re-released with digital tracks to take advantage of the improvement. Analog audio on LD wasn't all that great although CX audio encoding helped with the noise.

As I did not buy my first player or laserdiscs until maybe around 1988/89, that would certainly explain why I don't remember digital audio not being around.

[yoda313]

So, that method combines the 4 channels into a single stereo track? Is there any way to get only the center channel, for example?

Just to clarify there aren't true 4 channels in dolby surround. Read the main paragraph in the link Njroadfan provided:

Dolby Surround/Pro Logic is based on basic matrix technology. When a Dolby Surround soundtrack is created, four channels of sound are matrix-encoded into an ordinary stereo (two channel) sound track. The centre channel is encoded by placing it equally in the left and right channels; the rear channel is encoded using phase shift techniques, typically an out of phase stereo mixdown. A Pro Logic decoder/processor "unfolds" the sound into the original 4.0 surround—left and right, center, and a single limited frequency-range (7 kHz low-pass filtered[1]) mono rear channel—while systems lacking the decoder play back the audio as standard stereo.

It might have been encoded FROM a four channel source but they are not discrete in a dolby surround source. It has a mono rear channel and the center channel isn't discrete like it is in dolby digital.

I'm not a 100% certain on the differences between dolby surround and pro logic however. I am assuming its most likely an improved matrixing of the center channel for a clearer sound.

I did have both a dolby surround amplifier that was connected to a plain old stereo amp and a fully interegrated dolby pro logic surround amplifier. The dolby pro logic was definitely sharper than dolby surround but dolby surround worked. I don't believe I ever had a center channel for my dolby surround amp but I did for the dolby pro logic amp.

Obviously dolby digital and dts are the norms now with the true hd and dts-ma for bluray now.

Though you'll still dolby pro logic 2.0 only tracks on some dvd releases that didn't get a full remix treatment. Superman 4 on dvd comes to mind right away for that example. (at least the original single movie release - it might have received a 5.1 professional mix on the 4 disc set they released on dvd later but I don't have that version).

[Cornucopia]

IIRC, difference between DSurround and DProLogic and PL2 is that PL uses adaptive steering techniques on the decoder to increase the separation compared to DS. But both are still 4ch. PL2 uses a different matrixing formula on both encoder and decoder and support 5ch. So it's not totally backward compatible.

Scott

[yoda313]

But both are still 4ch

But its not really 4 channel right? I mean not in the true sense of the word. Since its matrixed its not discrete. That was the reason for dolby digital to get discrete (one reason among others).

Its still technically "stereo" in that its only left and right correct? The center and rears are extrapolated not independent. Right?

@cornucopia - thanks for the detailing on ds and dpl. Though I thought dpl 2 was supposed to get a seudo 5.1 from any source?

[Cornucopia]

Re: 4ch, that's 4ch input to the matrix encoder and 4ch output from the matrix decoder. It's only "stereo" in between.

It IS still 4ch, but that is the difference between matrixed and discreet. Matrixed is "dirty", compromised. But it is a form that is "compatible" within the constraints of stereo, whereas discreet is not.

Scott

[yoda313]

Re: 4ch, that's 4ch input to the matrix encoder and 4ch output from the matrix decoder. It's only "stereo" in between.

It IS still 4ch, but that is the difference between matrixed and discreet. Matrixed is "dirty", compromised. But it is a form that is "compatible" within the constraints of stereo, whereas discreet is not.

Scott

Ok. Thanks for clarifying.