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5.1 Surround Sound
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spiney2
14-02-2015
Originally Posted by chrisjr:
“Wasting your breath. It's been pointed out many times that you only get 5.1 over a two channel link if it has been through something like Dolby ProLogic encoding. Raw stereo mixed for stereo does not contain any surround information (any that is there is purely unintentional) nor does a 5.1 mix down mixed to 2 channel with no processing at all.”

at the risk of provoking further trolls, what i actually said was, where surround sound exists at all, then it is always on the 2.0 version as well as 5.1. Subject to the dolby matrix limitations, obviously. And clearly, producing a 2.0 mix from 5.1 must involve "processing". Not that this helps the OPer who cant get the prologic to accept the 5.1 datastream .......
chrisjr
14-02-2015
Originally Posted by spiney2:
“at the risk of provoking further trolls, what i actually said was, where surround sound exists at all, then it is always on the 2.0 version as well as 5.1. Subject to the dolby matrix limitations, obviously. And clearly, producing a 2.0 mix from 5.1 must involve "processing". Not that this helps the OPer who cant get the prologic to accept the 5.1 datastream .......”

No what you actually said is

Quote:
“full surround sound is provided on 2.0 audio ie the 2 channel version. But doesnt work as well as 5.1 in domestic environment cos living room size is too small for haas effect to work properly.”

http://forums.digitalspy.co.uk/showp...1&postcount=39

Which is rubbish. Surround sound is ONLY available if it has been encoded from a 5.1 master down to 2 channels.

If however the 5.1 master has simply been downmixed to 2 channel by simply summing left front and left right to make the left channel (and similarly for the right) with the centre and .1 channels mixed equally into left and right then there is no deliberate surround information in the resulting two channel mix.

Encoding the six channels into two is what I meant by processing. Simple downmixing to two channel is not the same thing at all.
spiney2
15-02-2015
i hav given a correct explanation of how dolby surround works, several times. Only because idiots repeatedly say "there is no surround sound on 2.0". Which obviously is rubbish. I dont much like giving repeated explanations for idiots. Or repeatedly being banned for it either.
spiney2
15-02-2015
i suppose i will have to give a detailed explanation. Wih rerences. Perhaps the mods will wait a bit this time, eh ?
spiney2
15-02-2015
I would like to be able to say – quite correctly – that where surround sound exists, it is always on 2.0 as well as 5.1. Without attracting trolls, then getting banned for a month. So, perhaps the mods would like to read what follows, very carefully indeed, before simply making a knee-jerk reaction ? If u dont understand it ask someone who does! No shame in that .........

As everyone knows, pro logic 2 was invented by Jim Fosgate. So presumably, he should know how it works ……..

“Guttenberg: I guess this is a good time to ask: What, exactly, is the difference between the original Pro Logic and Pro Logic II?

Fosgate: They both have their roots in quad and SQ matrix-style encoding/decoding. The original Pro Logic had mono "band-limited" surrounds, PLII has "full-bandwidth" stereo surrounds. Since original Pro Logic was a film-oriented system, Dolby had to make sure the center/dialog channel was rock-solid. So they weighted the steering toward the center front channel, which shrank stage width on stereo recordings. When Pro Logic came out, it was a marvel of performance and stability”

http://www.stereophile.com/content/j...nd-mind-page-2
http://en.wikipedia.org/wiki/Jim_Fosgate

That’s right. The same matrix (more or less) is used in SQ, the 2.0 cinema analogue soundtrack version, and pro logic. All based on peter schrieber's original patents. There are minor differences in matrixing between sq, qs, and dolby surround (snce there is only 1 way to matrix 4 channels into 2!) But there are very big differences in how the various different decoders work!

The main difference with pro logic is an absence of projector weave effects, allowing the two surround channels to be full bandwidth, if this is on the original material. Plus the analogue noise reduction has already been stripped out, if it was there at all, of course.

“REGULAR MATRIX: DOLBY SURROUND

This was originally developed to make "Star Wars" under the name Dolby Stereo. It quickly became the preferred surround system for movies. Home movies were encoded in it, as were many phonograph records, cassette tapes, and CDs. Most soundtrack recordings are encoded in Dolby Surround because the movies they came from were so encoded. There are more recordings in this matrix than any other.
One difference from other systems is that the decoder adds a delay in the back channel before it goes to the speakers, and that back speakers (called surround speakers) are placed on both sides. This removes the problem of localizing the side images that other 4-corners matrices have. Also, applying identical signals to all of the inputs produces the nadir (n) modulation”

Of course, a pro logic decoder will also play sq and qs!

“If you play a matrix style quadraphonic record, (Stereo-4, SQ or QS), through your Dolby Pro-Logic II matrix decoder you will get 5.1 channels of sound. Actually, this works quite well. My experience is that the Dolby Pro-Logic II decoder works better at playing back matrix style quadraphonic records than the many of the purpose-built decoders of the quadraphonic era. Some records decode better than others. That is true whether one is playing back the quadraphonic records using the original matrix decoders or using a Dolby Pro-Logic II decoder. One can also us the Dolby Pro-Logic decoder to play back quadraphonic records. My experience is that the Dolby Pro-Logic II decoder is much superior”.

"Indeed, Dolby Pro-Logic was essentially the ultimate implementation of matrix quad :-"

http://www.audiokarma.org/forums/sho....php?p=5453602

Now on to wrongly named “mono surround”, which confuses lots of people. Obviously, there is no such thing, because it is a contradiction in terms! So Please pay close attention:

“The last stage splits the signal in two with ± 90-degree phase shifts before adding to the left and right outputs. Thus the surround signal is encoded in opposite polarity on the left and right channels, but is also phase-shifted in respect of the original left, right and centre channels. This last point is essential as it would not be possible to 'fly' sounds overhead from surround to centre, or from one side to the rear, without it.”


http://www.soundonsound.com/sos/sep0...oundsound2.asp

In other words, the “mono” channel is fully phase encoded with positional information, which is then matrixed in with +j and –J (see diagram). Which is how you get spaceships whooshing around the back of your head in star wars. As I previously explained, the haas (precedence) effect doesn’t work in smaller living rooms, which is why the entirely different pro logic decoder - used only in homes, not cinemas note ! - was developed! Even on the earliest cinema decoders, which DID just have one rear output for parallel wired speakers (not in series, obviously!), the phase encoding still gives quite good surround sound.

Pro logic uses "steering" instead !

There IS actually such a thing as “mono surround”, ie the rear effects channel on Todd AO (early 6 track magstripe). If this were mixed into either dolby surround or 5.1, it would give a very odd “point mono” source at the rear! So usually, it isn’t.

I trust this clears up the confusion.
spiney2
15-02-2015
...... a bit more ...... although all these implementations are just dolby surround, in fact some non-film material IS matrixed slightly differently, which allows pro logic decoders to "more easily" decide which rear speaker to use. Essentially, this "speads out" the 2 rear channels matrixing, since there is no "film weave" problem from a projector analogue sound head. But it's a minor variation on essentially the same thing.

http://en.wikipedia.org/wiki/Matrix_...atrix_4:2:4.29
spiney2
15-02-2015
..... as is also well known, for many years, dolby used the schieber patents without paying royalties! And there was a famous lawsuit ....... possibly, this is one reason dolby use such misleading terminology on their official website!

http://caselaw.findlaw.com/us-7th-circuit/1375730.html
spiney2
15-02-2015
..... matrixing is also used on extensions of 5.1, like 9.1, etc ............
spiney2
15-02-2015
...... my link to "you are surrounded" above is just page 2 of a 10 part article. Which is worth reading. Page 2 does explain the cinema matrix version quite clearly, with some tips for diy experimentation ..........
spiney2
15-02-2015
.... just to add, quite clearly, +j and -j matrixing gives 2 rear channels, exactly like the other quad matrices. Even if the dolby version first goes through a single channel, and then cinema surround speakers all wired in parallel (although, i dont think any of those basic decoders are still in service!).
spiney2
15-02-2015
scheiber eventually shared an emmy with dolby for surround sound ........ but only after a fight !

"It becomes evident that the original concepts for what has come to be known as "Dolby Surround' . . . were originally founded by Peter Scheiber." - Analog Devices Inc"

http://www.sptimes.com/2003/11/02/ne...ognition.shtml
spiney2
15-02-2015
Originally Posted by chrisjr:
“No what you actually said is


http://forums.digitalspy.co.uk/showp...1&postcount=39

Which is rubbish. Surround sound is ONLY available if it has been encoded from a 5.1 master down to 2 channels.

If however the 5.1 master has simply been downmixed to 2 channel by simply summing left front and left right to make the left channel (and similarly for the right) with the centre and .1 channels mixed equally into left and right then there is no deliberate surround information in the resulting two channel mix.

Encoding the six channels into two is what I meant by processing. Simple downmixing to two channel is not the same thing at all.”

many films only ever had a 2.0 analogue soundtrack,, but they had surround sound. For example, star wars, which most people saw in 35mm format on first release in 77.
spiney2
15-02-2015
2.0 can, of course, be re-mixed into 5.1. Exactly because there are 2 rear channels. Obviously, there are limitations to 2.0 matrixing, as explained in my "you are surrounded" link, so it will not be as good as if the original mix had been 5.1 !

added ...... i sometimes use dvd flick, which can produce 5.1 from 2.0 ! Never done it, since that would just waste space ............
spiney2
15-02-2015
oops, sorry, I seem to have missed out a link, above !

"REGULAR MATRIX: DOLBY SURROUND

REGULAR MATRIX: DOLBY SURROUND
Stylus Modulation Description Poincaré Sphere How To Play
Dolby Surround 4.1

Dolby Surround 4.1


This was originally developed to make "Star Wars" under the name Dolby Stereo. It quickly became the preferred surround system for movies. Home movies were encoded in it, as were many phonograph records, cassette tapes, and CDs. Most soundtrack recordings are encoded in Dolby Surround because the movies they came from were so encoded. There are more recordings in this matrix than any other.

One difference from other systems is that the decoder adds a delay in the back channel before it goes to the speakers, and that back speakers (called surround speakers) are placed on both sides. This removes the problem of localizing the side images that other 4-corners matrices have. Also, applying identical signals to all of the inputs produces the nadir (n) modulation.

L = l + .71f + .71bj
R = r + .71f - .71bj"




http://midimagic.sgc-hosting.com/quadrafon.htm
spiney2
15-02-2015
.... i am not sure what meaning chrisjr intends to convey. Obviously, if the source material is 5.1., and you deliberately omit the 2 rear channels, then of course they will not be on the 2.0 matrix. But why would you do that? Many modern professional decoders simultaneously output both 5.1 and 2.0 regardless of input ............
anthony david
15-02-2015
Film drama is recorded multitrack and mixed down to 5.1. Where Dolby optical tracks are required they are mixed down via a coder/decoder to sound as close as possible to the 5.1 version. The reason for this is that cinema systems default to the analogue optical track if for any reason the digital track, which is also optical, cannot be decoded. Such a default will probably only be for a very short period of time but should not be obvious to the audience if it happens. The printed analogue tracks have Dolby noise reduction, originally A later SR. I have watched this process carried out, I used to maintain our dubbing theatres sound desks, and it is not easy to get a good match.
spiney2
15-02-2015
Originally Posted by anthony david:
“Film drama is recorded multitrack and mixed down to 5.1. Where Dolby optical tracks are required they are mixed down via a coder/decoder to sound as close as possible to the 5.1 version. The reason for this is that cinema systems default to the analogue optical track if for any reason the digital track, which is also optical, cannot be decoded. Such a default will probably only be for a very short period of time but should not be obvious to the audience if it happens. The printed analogue tracks have Dolby noise reduction, originally A later SR. I have watched this process carried out, I used to maintain our dubbing theatres sound desks, and it is not easy to get a good match.”

perhaps you would like to explain more to the people who keep trolling me ?
spiney2
15-02-2015
I do not dispute that Ray Dolby had to do much development and testing before coming up with a system that worked reliably in cinemas giving a "good experience" to most of the audience, provided the decoder has been set up correctly. Which at first would have been entirely discrete components. (i still have an Amstrad cassette deck with dolby B implemented with discrete transistors). The problem is how it is very misleadingly described on the dolby website, as LCRS. Since there is no centre channel in the matrixed mix, that only comes out of the decoder !
chrisjr
15-02-2015
Originally Posted by spiney2:
“.... i am not sure what meaning chrisjr intends to convey. Obviously, if the source material is 5.1., and you deliberately omit the 2 rear channels, then of course they will not be on the 2.0 matrix. But why would you do that? Many modern professional decoders simultaneously output both 5.1 and 2.0 regardless of input ............”

It is very simple.

A two channel audio sound track only carries surround sound information if encoded from a multichannel source mix.

If the source mix is direct to stereo then there is no deliberate surround information included. A ProLogic decoder may be able to create a surround effect but it is entirely artificial compared to a multichannel mix encoded into 2 channels.

Similarly if you simply sum the rear channels with the fronts with no signal processing other than simple addition of the signals then the result is NOT a surround encoded mix.
spiney2
15-02-2015
Originally Posted by chrisjr:
“It is very simple.

A two channel audio sound track only carries surround sound information if encoded from a multichannel source mix.

If the source mix is direct to stereo then there is no deliberate surround information included. A ProLogic decoder may be able to create a surround effect but it is entirely artificial compared to a multichannel mix encoded into 2 channels.

Similarly if you simply sum the rear channels with the fronts with no signal processing other than simple addition of the signals then the result is NOT a surround encoded mix.”

I am still not sure what you are trying to say. Are you claiming that surround sound is impossible on 2.0, or just that the 2 rear channels of 5.1 are never matrixed into 2.0, so that for example, 2.0 sound on freeview has no surround component ?
spiney2
15-02-2015
Certainly, 2.0 matrixed surround sound is not as good as 5.1, for obvious reasons, but it is entirely real ...........
spiney2
15-02-2015
.... presumaby, the difficulty of reading a digital datastream from a 35mm film going through a shutter gate mechanism is one more reason why it is now obsolete !
spiney2
15-02-2015
..... as far as I know,, 1st film in dolby stereo was Lisztomania. Clockwork Orange was mixed in the format, but i think the prints were not dolby coded, just "academy sound".
anthony david
15-02-2015
Originally Posted by spiney2:
“perhaps you would like to explain more to the people who keep trolling me ?”

Difficult to know where to start but the following may interest you.

When 70mm was popular many dubbing theatres were not 6 track capable so some films had nothing on inner left or right. others carried a mix of outer L/R and centre. Projectionists sometimes found that the sound was better if the amps for tracks 2 and 4 were switched off. These tracks were used for Sensurround trigger signals as well as other things.

A company called Acoutec based in Sharston Manchester made a cinema surround sound system that bypassed the Dolby patent much to their annoyance. It was sold under the Rank brand name but not used in their Odeon cinemas. Films had to be advertised as being shown in surround sound, not Dolby Surround Sound, which was a main reason for its failure. The equipment was used in cinemas belonging to the Tatton group which owned Acoutec. When the Gatley cinema was sold to Apollo the Acoutec equipment was removed and genuine Dolby put in.

There are similarities between Dolby Pro Logic and Sansui's QS Varimatrix. Sansui provided the chips for some early Dolby decoders.

Once you start investigating these things you soon open a can of worms. Where do Fantasound and Perspecta fit in?
spiney2
15-02-2015
..... and ultra stereo. And the Metro cinema Soho briefly used something else ...... all these systems evaded the dolby noise reduction patents .........

I have not mentioned noise reduction at all, as it is not directly relevant to surround matrixing ........
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