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Dolby Surround on Analog Tracks

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Anonymous
February 28, 2005 8:38:41 PM

Archived from groups: alt.video.laserdisc (More info?)

Earlier when I was updayting a couple titles at LDDB.com I was
wondering, if the back of the laser disc says "standard 2 channel
stereo track on the analog tracks" does that mean just 2 channel
stereo or Dolby Surround Sound. Can you have surround sound on the
analog tracks?
This appears on many DTS Laser Discs.


Ed
Anonymous
February 28, 2005 8:38:42 PM

Archived from groups: alt.video.laserdisc (More info?)

> Nitehawk^ <nighthawk_68@hotmail.com> wrote:

> ... if the back of the laser disc says "standard
> 2 channel stereo track on the analog tracks" does
> that mean just 2 channel stereo or Dolby Surround Sound.

It can mean surround. Some early titles may have
used the two-channel theatrical surround mix for
the LD audio.

> Can you have surround sound on the analog tracks?

Yes, as long as both analog channels are used for
analog audio. If one is consumed by AC-3, then the
other is the mono mix.

> This appears on many DTS Laser Discs.

DTS uses the digital audio data band, and doesn't
usually affect the analog carriers.

For some old info on this, see:
<http://www.access-one.com/rjn/laser/laserdisc.html#Surr...;

--
Regards, Bob Niland mailto:name@ispname.tld
http://www.access-one.com/rjn email4rjn AT yahoo DOT com
NOT speaking for any employer, client or Internet Service Provider.
Anonymous
March 1, 2005 9:26:11 PM

Archived from groups: alt.video.laserdisc (More info?)

Any two-channel source can be Dolby Surround. Even an FM tuner if the
broadcaster sent a Dolby signal. The sound has to be "matrixed" which is
actually pretty simple.

To decode the center channel data, sound data that is exactly the same
between the left and right channels is removed from the left and right and
sent to the center speaker. meaning if you dump a mono signal into an
otherwise stereo sound-field, that mono data alone will go to the center
channel.

I'm not totally sure of the method used to extract the rear channel data.
I believe it involves taking a mono sound signal that you want in the rear
and inverting(aka phase shifting?) the signal in one of the two channels.

then when you "add" the sound data between the channels together, the
inverted signals cancel each other out and that cancelled-out signal is
removed from the left and right speakers and sent to the rear speakers.
(this is why the rear channel sound is only mono in dolby pro logic)

i *THINK* that info about the rear channels is correct, anybody who knows
better let me know because i'd be interested in this as I've always wanted
to program software to encode pro logic signals!!!!

-Mike
Related resources
March 22, 2005 7:47:46 PM

Archived from groups: alt.video.laserdisc (More info?)

"half_eaten" <half_eaten@nospam.yahoo.com> wrote in message
news:1364286076935f760f14e417de2da851@localhost.talkaboutvideo.com...
> Any two-channel source can be Dolby Surround. Even an FM tuner if the
> broadcaster sent a Dolby signal. The sound has to be "matrixed" which is
> actually pretty simple.
>
> To decode the center channel data, sound data that is exactly the same
> between the left and right channels is removed from the left and right and
> sent to the center speaker. meaning if you dump a mono signal into an
> otherwise stereo sound-field, that mono data alone will go to the center
> channel.
>
> I'm not totally sure of the method used to extract the rear channel data.
> I believe it involves taking a mono sound signal that you want in the rear
> and inverting(aka phase shifting?) the signal in one of the two channels.

Yes, you're right I think. It's a case of using phase reversal (like when
you swap the +/- wires of one speaker to create an out-of-phase signal to
the other speaker) and this difference is used to extract the surround
channel (or the centre channel, or both in combination, i don't know
really). Whatever the method, phase reversal is the key. I don't know if
the official Dolby website tells us how it is done, or maybe they don't
since it's a proprietary patented secret method.

>
> then when you "add" the sound data between the channels together, the
> inverted signals cancel each other out and that cancelled-out signal is
> removed from the left and right speakers and sent to the rear speakers.
> (this is why the rear channel sound is only mono in dolby pro logic)
>
> i *THINK* that info about the rear channels is correct, anybody who knows
> better let me know because i'd be interested in this as I've always wanted
> to program software to encode pro logic signals!!!!
>
> -Mike
>
Anonymous
March 22, 2005 7:47:47 PM

Archived from groups: alt.video.laserdisc (More info?)

> Rick <deNOBULLlorean@veridas.net> wrote:

> It's a case of using phase reversal (like when you swap the +/- wires of
> one speaker
> to create an out-of-phase signal ...

Basically correct.
<http://www.access-one.com/rjn/laser/laserdisc.html#Surr...;

--
Regards, Bob Niland mailto:name@ispname.tld
http://www.access-one.com/rjn email4rjn AT yahoo DOT com
NOT speaking for any employer, client or Internet Service Provider.
!