5.1 mixing - Home Theater Forum and Systems - HomeTheaterShack.com

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post #1 of 30 Old 10-24-08, 01:04 PM Thread Starter
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5.1 mixing

For those interested in the technical/creative aspects of sound work,
I'll be mixing my latest feature film, "What Really Frightens You" beginning
on Monday October 27, 2008 at Du Art.

This will be my first 5.1 mix. Up to now I've mixed in the standard 4 track
Dolby format for 35mm exhibition. Of course Dolby involves derived channels.
Left and right which are discrete and a phantom center channel and derived
rear channel which is slightly delayed in the processors. 5.1 mixing involves
a left and right stereo channel with the center channel for dialogue only
and stereo surround channesl (LR, RR). All are discrete.

What's a bit disorienting is the fact that the 5.1 format is unique to DVDs
(standard definition and blu ray) and is not one of the formats utilized in
35mm theatrical exhibition. So while I'm mixing in 5.1, it has to be adapted
to the standard Dolby stereo mix which is left, center, right and mono surround.
The .1 in the 5.1 format is for subwoofer effects.

Here's what's even stranger for me. The high definition master video tape only
has four audio channels. Channels 1 and 2 will contain the Dolby stereo mix
of the film out of which is the phantom center and derived mono rear channel.
Channels 3 and 4 will contain the M & E tracks which are the same as the Dolby
tracks but missing the dialogue channel for foreign release. The 5.1 mix is not
contained on the HD master videotape. It's on a .wave file that cannot be heard
until it's been authored to blu ray and standard DVD. I guess it's very unusual for
me to mix in a format that I will only hear at the mix and not hear again until the
film is released for home video. Also the concept that the mix is not contained on
the actual HD video master but a separate element. The commentary track is also
on a .wave file and cannot be heard until it's released on DVD.

I'll post what it's like mixing in this format after I finish for those who are interested...

Here's what the elements are for the mix.

Six tracks. Tracks 1 and 2 are dialogue for the center channel. Tracks 3 and 4 are sound
effects and Tracks 5 and 6 are the rear channels. Plus there are another two tracks for
the stereo music which we'll spread onto the rear channels (at 25 % volume) and another
two tracks of 'room tones' (stereo city sounds etc.) to mix into the front left and right
as needed.
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post #2 of 30 Old 10-24-08, 02:01 PM
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Re: 5.1 mixing

Now that is interesting Richard, I had always assumed there was a 5.1 track at the theater (at least for the last 10 years or so). Can I also assume this is true only for film? And that digital capture film will have 5.1? I may not have used the proper terminology so I hope you understand my questions.

If you have a minute, how about a little primer on the subject? I always find your posts very informative and interesting Richard.


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post #3 of 30 Old 10-24-08, 02:48 PM Thread Starter
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Re: 5.1 mixing

5.1 sound is not what's on a 35mm theatrical release print. It's unique to the DVD format which is why old movies have to be re-mixed to this. New movies can have
a 5.1 mix adapted to the current theatrical standards but they are different.
However, if a theater has a DLP it can show a DVD or digital download in the 5.1
set up providing the theater is wired for it.

On top of that, the Dolby optical release print has to be derived from a DAT Dolby
mix which is different than the 5.1 mix. In short, new movies have multiple mixes
not a single mix.

But believe it or not, a movie having multiple mixes was not uncommon after the
fifties. Before that (in the pre-1952 era) there was a single mono mix for all
US theatrical releases via the optical track negative which was mono.

"This is Cinerama" in 1952 introduced seven channel magnetic stereo (5 discrete
channels up front an a stereo rear channel in the back). This mix was on a separate
piece of 35mm magnetic film known as a 'fullcoat' and not on the release prints.

This was followed by four track magnetic stereo sound in the CinemaScope format
which was three channels up front and a mono rear channel in the back which was
rarely used. The tracks were inside and outside the 35mm film sprockets. However,
all CinemaScope movies also had a standard mono optical track mixed down from the
four track mix for theaters that wanted a wider screen but not the stereo sound
(which was most of them).

Then came the Todd-AO (aka 70mm) format which was six track stereo with five
channels up front and a mono rear channel. Dialogue, music and sound effects
were spread across all five front channels. The mono rear channel was not a
surround track but only used for direction sound effects. When a vehicle or
horse went from right to left channel it would continue for a few seconds into
the rear channel. Otherwise, it was silent for most of the movie. The reason was
that movie palaces weren't designed for this expanded sound field and the rear
channels were difficult to hear in the back of the huge 1000 seat theater.
When 70mm films were reduction printed to 35mm anamorphic they were
mixed down to two formats. 35mm magnetic stereo in the anamorphic
(CinemaScope) four track format and a single mono optical track version
too. So all films shot and/or shown in the 70mm format had three mixes.

In the seventies Dolby introduced the optical stereo format. The film would be mixed
in four track discrete stereo like a CinemaScope movie. From that a six track 70mm version could be 'blown up' by incorporating the low frequencies on the left and right channels into subwoofer sounds which were known as 'baby booms' at the time. They
would not used the extra two front channels other than for explosions which was
different than the Todd-AO 70mm format which used all the 5 front channels.
They would take the same four channel mix and create a two channel optical stereo mix where the center channel contained the 'common' sounds (dialogue) that weren't in both left and right channels into a phantom center channel and the sounds that went from right to left channels (the difference between them sent to the rear in a delay) creating the rear channel.

Then came three different types of six track digital soundtracks in the nineties. One
was contained on an interlocked CD-ROM (the DTS format) which was really digital
Vitaphone and then there was the SDDS tracks on the ousides of the sprockets and the
Kodak digital sound between the sprockets. Since these six track discrete format were
not reliable there was a standard two channel (derived center and rear) Dolby optical
track as a backup which would kick in if the digital tracks failed during exhibition.
The Kodak digital format is the one that survived although some theaters are still
set up for the DTS synchronized CD format and the rare 70mm prints that are made
use this system now instead of the six magnetic tracks on the release print.

Then for unknown reasons, when DVD was introduced in the mid to late nineties, they
created the 5.1 format which was different than any theatrical stereo format up to
that time which meant the old stereo 7, 6, 4 and 2 channels stereo mixes had to be remixed.

But as I said, any movie shown in Cinerama, 70mm or CinemaScope had three mixes
in the fifties and sixties. So what is the 'definitive' mix? Well for films exhibited in
multiple formats there isn't. There are different mixes of the same audio tracks which
you can evaluate separately as to their effectiveness in a specific venue.

So for many contemporary movies there will also be three mixes. A digital
six track mix, a Dolby derived four track mix and a DVD/Blu-ray 5.1 mix. Each
is different.

Sound confusing? Well it is for a producer like me who had to sound edit
and sound design to compensate for the different formats in each mix.
"One size" no longer fits all markets or venues. It's also considerably more
expensive to mix now that it was in the mono days.

Last edited by Richard W. Haines; 10-25-08 at 05:25 AM.
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post #4 of 30 Old 10-24-08, 03:02 PM Thread Starter
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Re: 5.1 mixing

Here's some audio trivia.

There's nothing new under the sun. Way back in the thirties, I found
some prints in the two channel optical sound format. I screened a print
of "Maytime" (an old three strip Technicolor musical in 35mm) which had
dual optical tracks rather than a single mono optical track. Some of the
studios used to make unique dual channal optical tracks which would be
played back as a single mono optical track with the single light optical
reader of the time. But if you play "Maytime" made in the late thirties
through an dolby decoder here's what you'll hear. The left channel will
contain the music and effects only. The right channel will contain the
dialogue only. This was obviously done so foreign distributors could replace
the right track with their own dubbed dialogue.

All Dolby did in the seventies (beginning with "Tommy", not "Star Wars")
was to take the dual optical tracks and mix them into a stereo left and right
tracks with a derived center and rear channel and even that wasn't new...
they had tried it with quandrophonic vinyl record albums previously. Or course
the main difference was that Dolby encoded their two channels with noise reduction
to reduce optical track hiss. As common sense dictates, if you split a single mono
35mm optical track in two, you'll be hearing two 16mm optical tracks which have
some hiss. Dolby compressed the sound but also made you lose some high end sounds.
Discrete channels are always superior to compressed audio tracks. The dual channel
optical tracks of the thirties were played as single mono optical tracks even though
there were two 'squiggly lines' in the track area. They weren't split in two like they
were in the seventies with two tiny optical lights reading the tracks rather than one.
For those who don't know what 'optical sound' is, check out the animated demonstration
in "Fantasia" (1940). Those tiny squiggly lines on the left side of the picture area
are photographed sound waves. Just as light shined through the picture image and
projected through lens gives you the image on screen, there is another tiny light
and lens aimed at those squiggly lines which reads them and transfers the photographed
sound waves into electronic signals which are then sent to the amplifier and speakers
like any sound electronic sound waves (record, CD, radio).

The advantage to both optical sound (stereo or mono) and digital sound (Kodak,
SDDS systems) is that the sound information was contained in the emulsion and
would last the life of the print and not degrade in storage. While the magnetic
sound of the fifties through the seventies sounded very good, the magnetic tracks
would wear out as you played them over and over shedding oxide particles and
degrade in storage. It would also cause the film to get 'vinegar syndrome' in the
long run since the oxide acted as a corrosive on the film stock. Most magnetic
prints would warp and buckle as they deteriorated. The fullcoat film in 35mm
(used for the master mix and Cinerama interlocked system) were even worse
in terms of becoming twisted, warped and shedding off the oxide. Very often
the transfer technicians who are re-recording the old fullcoats into the digital
sound formats only have one pass to get the sound off of it before all of the
oxide flakes off. Some keep their fingers on the sound head as it's being re-recorded
and most of the time they have to clean them off after the transfer since oxide
residue is all over the place. Magnetic stereo sound was not an archival format...
not that they cared back then. It also stinks to high heaven when it's deteriorating.
The fumes are so strong they bother your nose and eyes when you handle them.

Last edited by Richard W. Haines; 10-25-08 at 03:53 PM.
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post #5 of 30 Old 10-24-08, 04:08 PM
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Re: 5.1 mixing

Thanks Richard, thats very interesting information.
This is one of the reasons I love this Forum is that we have people that actually know things like this and are willing to share that info with the rest of us.

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post #6 of 30 Old 10-24-08, 04:54 PM
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Re: 5.1 mixing

Great info Richard, Thanks.

How about films like Monster? As i understand it, the soundtrack for this film was conceived and recorded in 5.1. Is this very common? And if so, how does a theater handle this,.... can I assume that even though it was designed as a 5.1 soundtrack that there are multiple mixes in this case as well?

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post #7 of 30 Old 10-24-08, 06:16 PM Thread Starter
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Re: 5.1 mixing

Yes. They would have to alter the two rear channels so they were mono rather
that stereo for a 35mm Dolby Optical track.

You can mix in the 5.1 format and adapt it to the others by combining tracks/
folding them down and so forth. However, the mixer will ask you whether you
want the sound field designed for home set ups or for theatrical exhibition.

The bottom line is that as much fun as it was to watch "Star Wars" in 70mm
six track stereo at the Loews Astor Plaza in NYC back in the seventies, you
will get a much better sound field at home since you can customize it for your
needs. All theater sound is a compromise depending on how wide and how long
the cinema is. In the case of the Astor Plaza, it was very long so the surrounds
really blasted from the back of the theater. I wouldn't want to sit in the back
rows as a resut.

One of the biggest differences in 5.1 is that they keep the dialogue in the center
channel only for most releases. This is so foreign distributors only have to replace
that channel with a dubbed track while leaving the left/right and two rear channels
the same. This is different than films mixed prior to the advent of DVD. They would
often have directional dialogue on all of the channels which mean foreign distributors
would have to remix the entire movie rathen than just replace that center track.

Of course older stereo movies in 7, 6 and 4 track have been re-mixed for 5.1.
There are complex ways of doing it and simple ways. The simplest way is to
take the music on tracks 1 and 3 and added them at 25 % into the two rear
channels which would contain the mono rear track otherwise. By adding stereo
music in two rear mono channels, it makes them stereo...in a limited manner.
They just take dialogue from the left and right and put it into the center only
and leave the rest of the soundtrack 'as is' in the original 4 track.

The complicated method is to add effects or enhance ones that were originally
recorded to make them more effective in 5.1. For example, "The Sand Pebbles"
blu ray contains both the original 4 channel mix along with a new 5.1 mix which
has stereo surrounds (they added more crowd ambience and spread the music
into those channels) and added some low frequency sub-woofer for the explosions.
I guess technically the 'official' mix is the one that Robert Wise created in 1966
but I prefer the new one which is more dramatic. I do miss the directional dialogue
and singing in the original 6 track versions of films like "Oklahoma!" though.
I guess one excuse is that even in larger home theaters, the screens aren't that big.
The justification for directional dialogue was for the huge movie palaces in the fifties
and sixties with 60 to 80 foot wide screens. In those cases having dialogue come
out of the center speaker when a person was on the far left side of the screen
would've been disorienting. "Ben Hur" was an example of extreme compositions
on a very wide image (2.76 x 1 anamorphic 70mm) with characters on opposite
sides of the ratio which is why the original 6 track and 4 track stereo prints had
very directional dialogue. Another curious technique in the fifites was to record
with multiple mikes on set. I saw the Radio City Music Hall restoration of "A Star
is Born" in 1980 which had the original 4 track mix. I could hear Judy move from
mike to mike across the CinemaScope screen as she walked. In other words they
had three mikes spread across the set to record people as they moved around.

Last edited by Richard W. Haines; 10-25-08 at 05:47 AM.
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post #8 of 30 Old 10-25-08, 07:22 AM
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Re: 5.1 mixing

Very interesting read Richard......... thanks

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post #9 of 30 Old 10-25-08, 01:27 PM
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Re: 5.1 mixing

Wow neat stuff, thanks for sharing! I was always under the impression that the Dolby Digital track imbedded between the sprokets of the film was the same as the soundtrack on dvd. I never realized what a process the transfer actually was.
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post #10 of 30 Old 10-25-08, 03:47 PM Thread Starter
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Re: 5.1 mixing

You're welcome. So I start 9 AM on Monday. I'll have to leave at 6:45 AM to
make sure I get to NYC and the mixing studio in time. I'm only 50 miles from
Manhattan but rush hour can be a nightmare. It will be very stressful but
once it's mixed I'm seeing my vision (and hearing it) for the first time. Until
a movie is completed, it's all in my head. Getting it on film and on DVD is
quite complex and you need steely determination and **** of steel to
make it happen.
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