I have noticed a number of discs in the database have a "dolby surround" image but when I look at the disc back cover it reads "dolby surround stereo" instead of "dolby surround ac-3 digital" and playing them doesn't kick my demodulator into work, i.e. is this dolby-mixed stereo rather than 5.1?

I'm trying to find out which versions of some movies actually have 5.1 but it's turning out to be harder than I thought.

Dolby Stereo Surround/Surround/Stereo is a matrixed soundtrack on stereo tracks that provide center and rear sound when decoded through a Dolby decoder.
They can be stored on the Digital Stereo tracks (PAL) or the Analog Stereo tracks (PAL/NTSC) or both.

Dolby Digital Surround/Digital/AC-3 is a different beast storing digital bits modulated on a single analog track and providing 5.1/6.1 discrete channels (no matrixed decoding needed but RF signal must be translated into a PCM bitstream via an AC3-RF decoder).

For AC3 soundtrack, you can look for either of these logos on the cover/sticker:

Earlier discs (here from Dead Presidents (1995) [5263 AS])



Later covers (here Ghost and the Darkness, The (1996) [LV 323503-WS])



If Left Analog Audio trakc is Mono and there is no CX encoding, it's a good sign since Dolby Digital AC-3 is stored on the Right Analog Audio track.

Julien

Thanks alot for the quick reply! That really cleared it up for me.

I'm guessing Dolby Stereo Surround/Surround/Stereo is rather old and unsupported on modern receivers?

I'm using a Yamaha YSP-4300 which doesn't even mention what signals it accepts through its analog connections...

It's pretty much supported by all A/V Amps. Decoding mode is usually called "surround" or "pro-logic".

Julien

Damn, mine can't do it. I tried the analog and digital outputs but it just reads as 2.0.

Is there a standalone decoder? My audio equipment supports pro logic IIx which seems like it can read an already decoded dolby surround (4.0 i guess) signal and sort of up-convert it to 7.1, but it can't read the original matrixed signal.

The basic analog/digital Surround sound is a 2-channel stereo soundtrack, but your Prologic-II mode will then turn it into 4.0 (or better).

You're all equipped already.

Julien

Dolby Surround Stereo/ Dolby Surround is 4 channels of audio. Left channel, right channel, center channel, surround channel(single/mono channel distributed to rear/side speakers).

Matrix encoding can fold these four channels into two. Multiple technics are used to do this such as phase shifts, blending/mixing. Now they are called left total and right total. When listened thru two speaker setup they sound stereo and human ear can not tell the difference between normal stereo and matrixed in (4ch folded in). So it is fully backwards compatible for user without surround systems.

When played thru Dolby surround decoders, they can unfold 4ch and distribute your speakers. Because there were many sound effect folded onto each other, it is common these sounds leak into other speakers.

These decoder are called dolby surround in theaters and dolby pro logic in home theaters. Latest itiration is dolby prolofic 2z. It uses more advance algorithms to unfold these channels and distribute upto 10 speakers. 2 heights 2 fronts 1 center 2 sides 2 rears 1 subwoofer. Prologic 2z can do 8 speakers (missing height speakers)
Dolby digital is 5.1 channels recorded separately and channel separation is much better than dolby surround and has no leaks.

However dont disregard dolby surround. It can and does sound really good. Some dolby surround tracks sound much better than dolby digital tracks. Furthermore dolby surround tracks are uncompressed on ld. Dolby digital is highly compressed in order to fit 5.1 ch into less space.

Thanks. I did some experimenting and seem to have gotten it to work with at least one disc using the digital stereo track. My system only lights up an LED for when it receives a 5.1 or greater signal, and doesn't seem to decode from the analog inputs, so it was confusing for a bit :p