To my understanding, Dolby Surround and Pro Logic are the same....is
this correct?

In any case....

Can someone please make me not so ignorant on this subject?

I suppose my first question would be, how is it encoded? What's the
process? Laying to tape or ProTools for example....

Once encoded, how is one to know that it's been encoded for Pro Logic
unless indicated by LtRt somewhere? What if it's not indicated?

I suppose I should give more detail to my situation....

Encoding Audio for DVD purposes off of say DigiBeta. How am I to know
whether I should flag it in the encoder panel for Dolby Surround? If I
flag it and it's not LtRt what happens? Would it be the same as if I
flagged it as Not Indicated? Is there a sure-fire way of telling
whether something should be or not? What about if your source is say,
Pro-Tools? Anyway of telling then?

Sorry....to add to that....Pro Logic DOES have a center channel
where-as DD does not.....but the ignorace still applies..... :-)

Matt wrote:
To my understanding, Dolby Surround and Pro Logic are the same....is
this correct?

No. Pro-Logic is a steering logic system that steers the "dominant signal"
to the center channel. This is used for home theatre systems to prevent
people from actually having to align their systems properly.

Theatrical systems and earlier home systems using Dolby Surround required
pretty precise matching of channel gains and responses in order to keep the
dialogue in the center and keep the dialogue from leaking into the surround
channels.

In any case....

Can someone please make me not so ignorant on this subject?

I suppose my first question would be, how is it encoded? What's the
process? Laying to tape or ProTools for example....

Signals common to both channels come out the center. Signals specific to
one channel come out the sides. Signals opposite from one another in both
channels are Dolby B decoded, low-pass filtered, and sent out the surround
channel.

If you mix to the center, it comes out the center. If you mix to the center
with one channel inverted, it comes out the surround (and to a lesser extent
out the right and left channels). If you mix to hard right or hard left, it
comes out the right or left channel (and to a lesser extent to the surround
channel).

To use the Pro Logic gadget, there has to be substantial midrange activity
in the center channel to keep the stereo image centered. This works very
well for film sound work where the Pro Logic gadget keys on the dialogue and
adjusts the channel gains to keep the dialogue in the center. With music,
it is something of a problem in my opinion.

Once encoded, how is one to know that it's been encoded for Pro Logic
unless indicated by LtRt somewhere? What if it's not indicated?

Because the leader of the film says on it "DOLBY SURROUND-- A" or
"DOLBY SR" if it's SR-encoded with surround so that the projectionist
knows which button to push on the decoder. Or it might say "NON-DOLBY STEREO"
or "MONO." Or it might just have a number on it which is the code for the
Dolby decoder box.

Encoding Audio for DVD purposes off of say DigiBeta. How am I to know
whether I should flag it in the encoder panel for Dolby Surround? If I
flag it and it's not LtRt what happens? Would it be the same as if I
flagged it as Not Indicated? Is there a sure-fire way of telling
whether something should be or not? What about if your source is say,
Pro-Tools? Anyway of telling then?

Why would you want to use Dolby Surround for DVD? DVD allows you to use
modern encoding for full discrete 5.1 rather than having to work with cheesy
matrix systems to jam surround onto two stereo channels. If you're going to
DVD, go full 5.1.
--scott

--
"C'est un Nagra. C'est suisse, et tres, tres precis."

In article .com,
Matt wrote:
Sorry....to add to that....Pro Logic DOES have a center channel
where-as DD does not.....but the ignorace still applies..... :-)

No, they all have center channel outputs from the decoder.

Dolby Digital is a full 5.1 format, not a matrixed stereo format.
It is not related in any way to Dolby Surround or to Dolby Pro-Logic.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."

In article ,
(Scott Dorsey) wrote:

In article .com,
Matt wrote:
Sorry....to add to that....Pro Logic DOES have a center channel
where-as DD does not.....but the ignorace still applies..... :-)

No, they all have center channel outputs from the decoder.

Dolby Digital is a full 5.1 format, not a matrixed stereo format.
It is not related in any way to Dolby Surround or to Dolby Pro-Logic.
--scott

The original consumer (home) "Dolby Surround" had no center channel. The
older theater format, often called simply "Dolby Stereo", did have a
center channel even though the early home decoders did not. The newer
home format with the center channel is pro-logic, while the newer
matrixed format for theatrical release is usually just called Dolby SR
in Hollywood circles. This refers not only to the use of SR noise
reduction as opposed to the A-type used in the older format, but in
post, saying "SR" usually implies that it's LtRt, not just L,R with
noise reduction. Further, the 5.1 digital format is often referred to as
Dolby SR-D, referring to the digital 5.1 with the SR backup on the same
print. Dolby Digital is available for consumers in the home, and the
name also appears in the logos for SR-D theatrical releases. Is that all
confusing enough? The 4th article on the tech talk page at
promastering.com has some more info. Anyway, getting back to the thread,
the stereo PCM tracks on a DVD often have the LtRt while the "Dolby
Digital" AC-3 tracks have the discrete 5.1. But remember, it's not
always 5.1 just because it's Dolby Digital. Sometimes it's 5.0, 2.0, or
even mono.