Archive-Name: movies/tech/part2
Posting-Frequency: monthly
Last-Modified: 6/96
Version: 0.02

          /-----------------------------------------------------------\
          |                   rec.arts.movies.tech                    |
          |             Frequently Asked Questions (FAQ)              |
          |                      (with answers)                       |
          |                                                           |
          |                       Part 2 of 4                         |
          |                                                           |
          |                       Version 0.02                        |
          |            (supersedes all previous versions)             |
          |                        June, 1996                         |
          |                                                           |
          |                                                           |
          |              Compiled, Edited, Maintained by              |
          |                     Scott E. Norwood                      |
          |                     snorwood@nyx.net                      |
          \-----------------------------------------------------------/
                      Copyright (C) 1996 by Scott E. Norwood

          This document may be freely distributed by electronic, paper,
          and  other  means, provided  that  it is  distributed in  its
          complete,   unmodified   form   for   non-commercial   and/or
          educational   purposes.    Commercial  use  of  the  material
          contained   herein  is  not  permitted, unless prior  written
          permission  is  obtained from the  copyright  holder.  Others
          who  have  contributed to this  document retain the rights to
          their own contributions (which are noted).

                                   DISCLAIMER:

          The  compiler  of  this  document has attempted to make every
          reasonable effort  to ensure that any  information  contained
          herein  is accurate  and complete.  However, the compiler  is
          unable to assume responsibility, legal or  otherwise, for any
          inaccuracies, errors,  or omissions  relating  to the inform-
          ation contained below.  All of  the information  contained in
          this document is believed by its compiler to  be held  in the
          public  domain.  The  compiler is  not affiliated with any of
          the  companies whose products are mentioned here, nor does he
          necessarily endorse these products. All statements about such
          products  are  for informational  use only.  U.S.  trademarks
          are indicated  by (tm)  where applicable,  and  are used here
          without the permission of their owners.

                    -----------------------------------------

TABLE OF CONTENTS:

3.0  Motion Picture Formats (release prints intended for projection)

  3.1   Which film gauges are currently in common usage for release
        prints intended for projection?
  3.2   Why is wide-gauge film manufactured in the 65mm width for motion-
        picture cameras, and in 70mm for release prints?
  3.3   Which formats and aspect ratios are common for 8mm release prints?

    3.3.1   Regular 8mm/Super 8mm
    3.3.2   Regular 8mm/Super 8mm Anamorphic

  3.4   Which formats and aspect ratios are common for 16mm release prints?

    3.4.1   Regular 16mm
    3.4.2   16mm Anamorphic
    3.4.3   Super 16mm

  3.5   Which formats and aspect ratios are common for 35mm release prints?

    3.5.1   35mm Silent Frame
    3.5.2   35mm Academy Frame
    3.5.3   35mm 'Flat' Wide Screen Formats
    3.5.4   35mm Anamorphic Frame
    3.5.5   Projecting Multiple Formats

  3.6   Which formats and aspect ratios are common for 70mm release prints?

    3.6.1   70mm Standard Frame
    3.6.2   70mm IMAX (tm)/OMNIMAX (tm) 15-Perf Frame

4.0  Motion Picture Sound Formats (release prints intended for projection)

  4.1   What analog sound formats are common for 8mm release prints?

    4.1.1   Regular 8mm Magnetic  (monophonic)
    4.1.2   Super 8mm Magnetic  (monophonic or stereo)
    4.1.3   Super 8mm Optical  (monophonic)

  4.2   What analog sound formats are common for 16mm release prints?

    4.2.1   16mm Optical  (monophonic)
    4.2.2   16mm Magnetic  (monophonic)

  4.3   What analog sound formats are common for 35mm release prints?

    4.3.1   35mm Optical  (monophonic, stereo, or Dolby Stereo (tm))
    4.3.2   35mm Magnetic  (four-track stereo)

  4.4   What analog sound formats are common for 70mm release prints?

    4.4.1   70mm Magnetic  (six track stereo)

  4.5   What are the three commonly used digital sound formats for 35mm
        release prints, and how do they work?

    4.5.1   General Information
    4.5.2   Digital Theater Sound (DTS) (tm)
    4.5.3   Sony Dynamic Digital Stereo (SDDS) (tm)
    4.5.4   Dolby (tm) Spectral Recording Digital (SR-D) (tm)

  4.6   Which studios use which formats for digital sound?
  4.7   What methods have been used for digital sound in formats other
        than 35mm?

                    -----------------------------------------

3.0  Motion Picture Formats (release prints intended for projection)
--------------------------------------------------------------------

  3.1   Which film gauges are currently in common usage for release
        prints intended for projection?

     Currently:  8mm
                 16mm
                 35mm
                 70mm

  3.2   Why is wide-gauge film manufactured in the 65mm width for motion-
        picture cameras, and in 70mm for release prints?

  [under construction]

  3.3   Which formats and aspect ratios are common for 8mm release prints?

     regular 8mm     (projection frame:  .172" x .129")  (standard frame)
                     (projection frame:  .172" x .129")  (anamorphic frame)

     super 8mm       (projection frame:  .209" x .156")  (standard frame)
                     (projection frame:  .209" x .156")  (anamorphic frame)

    3.3.1   Regular 8mm/Super 8mm

     Regular 8mm has a projected aspect ratio of 1.33:1, matching the 35mm
silent frame.  Super 8mm has a similar projected aspect ratio of 1.34:1.
Release prints in regular 8mm usually do not have a soundtrack, although
a few do.  Super 8mm prints often have a magnetic or optical soundtrack,
located on the edge of the film opposite the perforated edge.  Films with
magnetic sound also have a 'balance stripe' on the perforated edge
in order to keep the film thickness even, although sound is not normally
recorded on it.

    3.3.2   Regular 8mm/Super 8mm Anamorphic

     Many 8mm reduction prints of 35mm anamorphic original films are printed
in a 2:1 squeeze ratio, which retains the original side framing, but crops
off a small portion of the top and bottom of the frame.  The final
aspect ratios are 2.66:1 and 2.68:1 for regular 8mm and super 8mm, 
respectively.  Projection of these films, obviously, requires an anamorphic
lens for the projector in order to 'unsqueeze' the image.  These lenses
are, unfortunately, difficult to find, and often expensive, despite their
less-than-perfect image quality.

regular 8mm release print frame:   super 8mm release print frame:
  (note big perforations)            (note small perforation)

  |                  |               |                  |
  |s-------------- O |               |s---------------- |
  |o|    Small   | | |               |o|     Larger   | |
  |u|    Image   | | |               |u|     Image    |o| <--- Smaller
  |n|    Area    | | |               |n|     Area     | |    Perforation
  |d-------------- O |               |d---------------- |
  |                  |               |                  |

  |<------ 8mm ----->|               |<------ 8mm ----->|

  3.4   Which formats and aspect ratios are common for 16mm release prints?

     16mm            (projection frame:  .373" x .272")  (standard frame)
                     (projection frame:  .373" x .272")  (anamorphic frame)

     super 16mm      (projection frame:  .468" x .282")  (super 16mm frame)
                     (projection frame:  .468" x .253")  (1.85 s16mm frame)

    3.4.1   Regular 16mm

     When 16mm was first developed, 35mm silent films were shot for
projection in an aspect ratio (width to height ratio) of 1.33:1; thus, the
16mm aspect ratio of 1.37:1 was designed to be relatively close to the
35mm one.  Unlike 35mm, however, no modification of aspect ratio was needed
in order to accommodate sound-on-film prints (the sound is printed on one
edge of the film, in the space formerly occupied by a second set of sprocket
holes [which are still present in todays 'double-perf' camera films]), and
so the aspect ratio of 16mm remains unchanged.

     Unlike camera films, 16mm release prints are almost always single-
perforated--i.e.  the film has perforations on only one side of the
image.  The other side is reserved for a soundtrack.  The only exception
to this are lab workprints from double-perf camera stock, which are also
printed on double-perf stock, mostly for convenience in splicing with
a 'guillotine'-style tape splicer, commonly used by editors.

    3.4.2   16mm Anamorphic

     Although it is not a 16mm shooting format, 16mm reduction prints of 35mm
anamorphic original films are often printed in a 2:1 squeeze ratio, which
retains the original side framing, but crops off a small portion of the top
and bottom of the frame.  Projection of these films, obviously, requires an
anamorphic lens for the projector in order to 'unsqueeze' the image.

    3.4.3   Super 16mm

     This is designed as a shooting format, and not for exhibition purposes,
but projectors are manufactured for this format, primarily for the purpose
of screening super 16mm dailies for a project which is intended for
television or 35mm blowup.  Standard 16mm projectors can also be modified
for this purpose, by filing out the gate (a fairly simple procedure).  Most
super 16mm projectors are found in laboratory screening rooms or are owned
by location rental houses.  They are almost never used for general film
exhibition, except maybe for the occasional film festival.

16mm release print frame:

  |                  |
  |sO--------------O |
  |o|     Image    | |
  |u|     Area     | |
  |nO--------------O |
  |d                 |

  |<----- 16mm ----->|

  3.5   Which formats and aspect ratios are common for 35mm release prints?

     35mm            (projection frame:  .94"  x  .71")  (silent frame)
                     (projection frame:  .825" x .602")  (Academy frame)
                     (projection frame:  .825" x .497")  (1.66 European)
                     (projection frame:  .825" x .471")  (1.75 - obsolete)
                     (projection frame:  .825" x .446")  (1.85 US standard)
                     (projection frame:  .825" x .690")  (anamorphic frame)

    3.5.1   35mm Silent Frame

     In the early days of 35mm silent film, the standard aspect ratio
was 1.33:1, and the image covered nearly the whole area of the film,
four perforations high, and extending out to the edges of the perforations
on the sides.  These prints are almost extinct today, as they leave no
space for a soundtrack, and, thus, the format became obsolete upon the
introduction of sound on film in 1926.  At this time, the frame was simply
narrowed, to the almost-square 1.15:1 ratio in order to accommodate an
optical soundtrack.  This is the area used by the current anamorphic
format, and is the most image area one can fit onto a piece of 35mm
film with a soundtrack.  As very few venues are equipped to project
silent-frame prints, this format is almost non-existent today.

    3.5.2   35mm Academy Frame

     When it became clear that nearly all future prints would contain sound-
tracks, the 35mm frame was cropped at the top and bottom slightly in order
to achieve a 1.37:1 frame, nearly matching the old silent frame.  This
Academy frame is the basis for nearly all future 'flat' (non-anamorphic)
formats, as well as the various television formats currently in use.

    3.5.3   35mm 'Flat' Wide Screen Formats

     With the introduction of CinemaScope (tm) in 1953 (see below), there
came a demand to release all films in a 'wide' aspect ratio.  This was most
easily achieved by cropping off the top and bottom of the Academy frame
in the projector.  While most prints still contain the full Academy
frame-size image, the tops and bottoms of it are cropped off in the
projection process.

     There are several commonly used formats which use this principle, of
which the most common currently is the U.S. standard of aspect ratio
1.85:1, used on almost all 'flat' prints currently in circulation.  One of
the major disadvantages of this format, however, is its terrific
inefficiency of negative space.  Although the camera and projector both
move the film four perforations at a time (the height of the Academy
frame), the actual projected image only takes up 2.5 frames.  Thus, images
are grainier and less sharp than those of Academy films projected on the
same height screen.

     The proposed 2.5-perf format (described elsewhere in this FAQ) does
not change the area of the 1.85:1 frame, but simply moves the film
a shorter distance (2.5, rather than 4 perforations) between frames,
using less film per unit of running time.

     A few films made in the 1950's were made to be projected in the 1.75:1
aspect ratio; while this is no longer a common projection ratio, it is
interesting now, because it corresponds very closely to the 1.77:1 proposed
U.S. High Definition Television (HDTV) standard, designed as a compromise
in order to fit both 1.37:1 television material and wide screen feature
films onto the same size screen.

     The standard frame ratio in Europe is still 1.66:1, the same as
the super 16mm standard.  These films are almost never shown properly
in the U.S., however; most are simply cropped to fit onto screens masked
for 1.85:1.

    3.5.4   35mm Anamorphic Frame

     This frame is the same size as the ~1.15:1 frame used just after
the introduction of sound-on-film, and represents the most efficient
use of film area possible, while allowing space for a soundtrack.
The 2.0x 'unsqueeze' achieved during the projection of the film with
an anamorphic lens provides one of several aspect ratios, depending
upon the projector mask to be used.

     The first CinemaScope (tm) (anamorphic) feature was _The_Robe_,
released by Fox in 1953.  These prints were made with tiny 'Fox hole'
perforations, and contained four tracks of magnetic sound (quite impressive,
particularly in a time when most movie-goers had not even heard regular
stereo!).  Due to the narrow perforations, an aspect ratio of 2.55:1 was
achieved.

     In 1956, the 'scope ratio was narrowed to 2.35:1 in order to accommodate
both magnetic and optical tracks on the same print (so that it could
be shown in theaters not yet equipped with magnetic sound equipment).  This
ratio was retained until 1971, when the height was reduced slightly, 
resulting in a 2.39:1 aspect ratio, in order to better hide lab splices.

     In 1994, the height and width were reduced proportionally, retaining
the 2.39:1 aspect ratio, which is the current standard.

    3.5.5   Projecting Multiple Formats

     These formats are all standard, although each requires its own
projector mask (to cover up the unused image area) and lens (to ensure
that the image properly fits the screen).  If necessary, the anamorphic
lens and mask can be used to show 1.37:1 Academy films, provided that the
anamorphic lens element is unscrewed and removed first, and the curtains
are adjusted to mask the 1.37:1 area (which will be very small).  Most
theaters keep the top and bottom edges of the screen at the same heights,
and open curtains on either side of the screen in order to accommodate the
wider formats, as shown below (not to scale):

                    ----------------------------------------
                c)  |  |   |  |                  |  |   |  |  (c
                u)  |  |   |  |                  |  |   |  |  (u
                r)  |  |   |  |      Movie       |  |   |  |  (r
                t)  |  |   |  |      Screen      |  |   |  |  (t
                a)  |  |   |  |                  |  |   |  |  (a
                i)  |  |   |  |                  |  |   |  |  (i
                n)  ----------------------------------------  (n

                    ^  ^   ^  ^                  ^  ^   ^  ^
                    |  |   |  |----- 1.37:1 -----|  |   |  |
                    |  |   |-------- 1.66:1 --------|   |  |
                    |  |------------ 1.85:1 ------------|  |
                    |----------------2.39:1 ---------------|

     It should be noted that having separate lenses and masks for each
format is highly idealistic, and is not standard practice, except at
a few conscientious art houses, which must show prints from all time
periods and all countries.  Most U.S. theaters are only equipped to properly
show 1.85 and 2.39:1 ratios, lacking the appropriate lenses/masks and
ability to move the curtains to other ratios.  Thus, when prints intended
for other formats are shown, some of the image is usually cropped.  Some
theaters show everything at 2:1 (eliminating the need for changing the
screen masking), cropping some from all formats.

                                   35mm release print frame:
                                     (1.85:1 ratio)
                                     (usually, picture is visible above and
                                      below 1.85:1 framelines, but it is
35mm release print frame:             masked off, and does not show up on
  (Academy ratio)                     the screen)

  |                        |         |                        |
  |O   -------------------O|         |O    (unused space)    O|
  |  s |                 | |         |  s ------------------- |
  |O o |       Image     |O|         |O o |      Image      |O|
  |  u |                 | |         |  u |      Area       | |
  |O n |       Area      |O|         |O n |                 |O|
  |  d |                 | |         |  d ------------------- |
  |O   -------------------O|         |O    (unused space)    O|
  |                        |         |                        |

  |<-------- 35mm -------->|         |<-------- 35mm -------->|

  3.6   Which formats and aspect ratios are common for 70mm release prints?

  [under construction]

     70mm            (projection frame:  1.912" x .870")  (standard 70mm)

    3.6.1   70mm Standard Frame

     The standard 70mm frame has always has an aspect ratio of 2.2:1, which
is slightly narrower than 35mm CinemaScope (tm).  Often, 70mm blowup prints
are made of 35mm CinemaScope films.  These blowups are 'flat,' and often
provide better image quality due to the superior registration (image
steadiness) of the 70mm format, as well as the reduced grain imposed
by the release print (more grains per square foot of screen area).  This
was done more in the past (1970's through 1980's) because the high-quality
six-track discrete (as opposed to matrixed) soundtracks on 70mm prints
could not be equaled by 35mm optical Dolby Stereo (tm) tracks.  Several
innovations in 35mm, however, most notably digital sound (along with
Dolby (tm) SR, and reverse-scanning solar cells) rendered 70mm blowups
unnecessary if sound is the only consideration.  Further, the recent shift
toward 10-20-screen multiplex theaters, and the resultant smaller screens,
has lessened the impact of the larger, better-quality image.

     Much of the expense of making 70mm prints in the past has been the
magnetic striping which is necessary for the soundtrack, as there is no
such thing as 70mm optical sound.  With the possibility of printing a DTS (tm)
timecode on the 70mm print, and providing the actual soundtrack on DTS (tm)
CD-ROM disks (like with 35mm DTS (tm)), this may no longer be necessary,
possibly paving the way for a 70mm revival.  This remains to be seen,
however.

     In addition to the conventional sprocket holes, all 70mm prints also
have a small 'registration hole' punched every 5 perforations.  Theoretically,
this is supposed to line up with the frameline, but, in practice, this is
ignored, and it just occurs at a random point.  The primary purpose served
by the registration hole is for use as a splicing reference, so that
splices can always be made at the frameline, even in the middle of a fadeout
or a dark scene.

    3.6.2   70mm IMAX (tm)/OMNIMAX (tm) 15-Perf Frame

     These special formats are simple contact prints made from the
negatives (or intermediates).  Although they are wider (by 5mm) than the
original negatives, they never contain a soundtrack printed directly on
the film.  Sound is provided either by a separate, interlocked magnetic
tape, or by a CD-ROM disk, which is driven by a timecode on the
film (as in the DTS (tm) system used for 35mm digital sound).

70mm standard release print frame:
  (courtesy David Richards <daverich@netcom.com>)

  |XXoX|____________________________________|XoXX|
  |XX X|                                    |X XX|  'o' = sprocket hole
  |XXoX|                                    |XoXX|
  |XX X|                                    |X XX|  'X' = mag. track area
  |XXoX|                                    |XoXX|
  |XX X|                                    |X XX|  (registration hole not
  |XXoX|                                    |XoXX|   shown in this diagram)
  |XX X|                                    |X XX|
  |XXoX|____________________________________|XoXX|
  |XX X|                                    |X XX|

  |<---------------- 69.95mm ------------------->|
  |<---------------- 2.754in ------------------->|

                    -----------------------------------------

4.0  Motion Picture Sound Formats (release prints intended for projection)
--------------------------------------------------------------------------

  4.1   What analog sound formats are common for 8mm release prints?

     regular 8mm              magnetic   (variable frame offset)
     super 8mm                magnetic   (?? frame offset)
                              optical    (?? frame offset)

    4.1.1   REGULAR 8mm Magnetic (monophonic)

     While regular 8mm was never designed to have a soundtrack, someone
figured out that the edge opposite the perforations could have a thin
magnetic stripe applied to it in order to carry a recording of film's
soundtrack.  This, of course, uses the same principle as an ordinary
tape recorder.  Unfortunately, though, this format was never standardized,
and never received wide usage.  Complicating the issue was the wide variety
in the 'sound offset'--i.e.  the number of frames ahead of the picture that
the sound must run.  If a film with an 18-frame sound offset were run in
a projector which supported a 20-frame offset, then the sound would run
slightly behind the picture.  Sound quality here is quite variable, depending
upon the quality of the striping job, the age of the print, and the quality
of the recording.

    4.1.2   SUPER 8mm Magnetic (monophonic or stereo)

     Soon after super 8mm displaced regular 8mm as the standard home-movie
format, people began to demand sound capabilities for their cameras and
projectors.  The easiest way to record sound while shooting is to record
the sound within the camera on a magnetic stripe pre-applied to the edge
of the film, in the same manner as the various regular 8mm systems.
A 'balance stripe' is also applied on the sprocket-hole edge, but not
usually used for sound; its purpose is to maintain an even film thickness.
Aside from having two differing frame rates (18 fps and 24 fps), this
method became standardized for both cameras and projectors, with a
standard sync offset.  Sound quality is potentially quite good, with some
recording devices and projectors offering stereo reproduction by recording
twin soundtracks, one on the 'balance stripe' and one on the regular
sound stripe.

     The primary disadvantage to this system of recording sound in the
camera is that it makes good editing extremely difficult.  Super 8mm is
usually shot with reversal film (see below), meaning that the camera
original is edited and then projected.  In this case, after every splice,
there will be a delay of about one second between when the picture
edit shows up on the screen, and when the sound edit is heard; this is
a result of the sync offset of the soundtrack.  For this reason, professional
films (except old television news films) almost never record sound within
the camera, but rather use a 'double-system' method, in which the sound
and picture are kept on separate strips of film through the editing
process, until the final release prints are made.  Home movies, though,
rarely undergo substantial editing; thus, 'single-system' sound recorded
in camera is useful and convenient.

    4.1.3   SUPER 8mm Optical (monophonic)

     While magnetic sound is of high quality, it can be expensive,
particularly for large print runs.  For this reason, optical soundtracks,
of the type used for 16mm and 35mm prints, eventually found their way
onto some 8mm films (usually, commercially released ones).  Only a few models
of projector could reproduce this type of soundtrack, however, and quality
is less than desirable, due to both the relatively slow linear speed at which
the film moves past the soundhead, and the inherent limitations of frequency
response and noise on an optical track (see description for 16mm optical
for more details).

  4.2   What analog sound formats are common for 16mm release prints?

     16mm                     optical    (26 frame offset)
                              magnetic   (28 frame offset)

    4.2.1   16mm Optical (monophonic)

     The first sound-on-film 16mm prints, made in the 1940's, used an
optical system, like that used on the 35mm prints of the time.  An optical
track consists of an image of a 'wave'-like clear band which allows differing
amounts of light to pass through it upon playback (this is called a 'variable
area soundtrack'; 'variable density soundtracks' were also tried at one
time--they did not use a band of clear film, but rather the entire soundtrack
area varied in density, or transparency.  This gave a slightly better
frequency response than a variable-area track, but resulted in increased
background noise, due to film grain.  They are no longer used).  The sound
is reproduced by means of an exciter lamp, which shines through a small
lens onto the optical track area of the film.  This light is focused onto
a solar cell on the opposite side of the film.  The solar cell varies its
electrical resistance based upon the amount of light which is shining on
it.  Thus, as the 'wavy' band gets wider, more current can pass through the
solar cell, which causes the loudspeaker to vibrate more, which results in
a louder sound.  This system is rather primitive, but it is inexpensive,
as the sound is printed on the film at the same time as the picture,
whereas magnetic systems require a separate 'sounding' step after the
picture is printed.

     Sound quality is not particularly good, but has been improved in recent
years by the printing of two identical tracks which are adjacent to each
other.  This method allows the two tracks to cancel out each other's
flaws or at least to cover them up.  Thus, the noise problem is substantially
reduced, but the limited frequency response continues.  Although it is
technically possible to produce a stereo optical track in 16mm, no one has
yet exploited this potential, as there is no commonly available equipment
to shoot a stereo track, or to reproduce it.

    4.2.2   16mm Magnetic (monophonic)

     In an attempt to improve the sound quality for 16mm prints, magnetic
sound was developed in the early 1960's.  This, like 8mm magnetic, used
a magnetic strip which was placed in the same location as the optical track.
The problem with this system was that, while it sounds quite good, few
projectors are capable of reproducing it.  Thus, its use was pretty much
reserved for television news (until the late 1970's, when news film was
replaced by videotape); news cameras, such as the Auricon and the CP-16, were
modified to record magnetic sound directly onto pre-striped reversal stock.
This film was developed at TV stations, and was then run through a
'magnetic offset recorder,' which simultaneously played the soundtrack,
and re-recorded it 28 frames earlier, so that the film could be edited
with the sound in perfect sync.  The film was again run through the
offset recorder, this time to re-advance the soundtrack 28 frames
after the picture so that it could be played back in sync on the station's
film chain machine.  This was the solution to the sync problem common with
super 8mm films with recorded-in-camera-sound.

  4.3   What analog sound formats are common for 35mm release prints?

  [under construction]

     35mm                     optical    (?? frame offset)
                              magnetic   (?? frame offset)

    4.3.1   35mm Optical (monophonic, stereo, or Dolby Stereo (tm))

     The standard sound-on-film system for 35mm has always been optical
sound.  This works like the variable-area system described above under
'16mm optical.'  This system is inexpensive and standardized, so that
almost every projection setup in the world is capable of reproducing it.
Of course, the disadvantages are as with any optical sound system:  lousy
frequency response, noise, and 'pops' when splices pass through the soundhead.

     Eventually, in 19??, the standard monophonic track was modified to
permit stereo reproduction.  This allowed optical tracks to offer com-
petition to the four-track magnetic systems in use at the time.  The
reproduction of stereo tracks required modification of the projector's
soundhead to accept a stereo solar cell.  In the mid-1970's, Dolby (tm)
Laboratories developed methods of 'matrixing' the SVA (stereo variable area)
track in order to encode four tracks worth of information within the twin
stereo tracks.  This allowed for the additions of a center (dialogue) track
and a rear 'surround' track to the usual left and right stereo tracks.  In
addition, Dolby (tm) type 'A' noise reduction was used to reduce background
noise.  This 'Dolby Stereo (tm)' system soon became standard, and nearly all
commercially released films since about 1980 have been encoded with it.  Of
course, one must use a Dolby (tm) Cinema Processor (or a clone thereof [e.g.
'Ultra Stereo']) in order to decode and reproduce all four tracks;
otherwise, it just reproduces as two-track stereo.  'DTS Stereo (tm)' uses the
same principles as Dolby Stereo (tm) and is decoded with the same equipment,
but the term applies to optical tracks produced by DTS (tm), without the use
of Dolby (tm) equipment (Dolby (tm) encoding equipment is usually rented out
for higher rates).  Note that 'DTS Stereo (tm)' is distinct from the DTS (tm)
digital sound system described below.

     In the late 1980's Dolby Stereo (tm) was improved upon by 'Dolby
SR (tm).'  The 'SR' stands for 'spectral recording,' which incorporated
better channel separation and noise reduction than standard Dolby Stereo (tm),
but which supposedly retained compatibility with Dolby (tm) type 'A'
processors, although this is debatable.  A Dolby (tm) 'A' processor can
be upgraded to support SR prints, if desired.

     Incidentally, Dolby (tm) 'A' noise reduction is one of several noise
reduction schemes developed by Dolby (tm) Laboratories.  It (and SR) are
capable of reducing noise across the entire audible frequency range.  Dolby
(tm) also developed type 'B' noise reduction, which reduces the high-
frequency noise common to audio cassette tapes, and type 'C' noise
reduction which is also used for cassettes, as well as the Beta SP videotape
format.

    4.3.2   35mm Magnetic  (four-track stereo)

    When the first CinemaScope (tm) films were produced, Fox had special
release print stock made up, which contained very narrow perforations (known
as 'Fox holes').  The idea behind this was to allow for a magnetic sound-
track containing four discrete (not matrixed) tracks (in the same L/C/R/S
configuration as the modern Dolby Stereo (tm) setups).  At the time, the
'scope image was wider than it is now (because it extended into the
area now used for optical tracks), and thus could not fit an optical track
on the print.  The magnetic stripes were applied in the same manner as
to 70mm prints.

     This idea worked reasonably well, and was used for a number of years
(through the early 1970's) on 35mm prints of all formats (only 'scope
prints required the Fox holes, though), and the sound quality was
excellent, even by today's standards, provided that the magnetic tracks
were in good condition.  The problem of this scheme was that, unlike
optical sound, magnetic tracks were not a permanent part of the film, and
could be intentionally or accidentally erased, simply by being placed
too close to magnetic fields, like those found in electric motors (such
as those used on rewind benches).  Even reels and cans can become magnetized,
usually erasing all or part of the magnetic track, requiring that it
be re-dubbed, at great expense.  Further, the magnetic sound heads
required frequent cleaning in order to keep them sounding good.

     With the invention of Dolby (tm) 'A' noise reduction and the application
of this technology to optical tracks, magnetic sound lost some of its
quality advantage over optical, and was substantially more expensive
than optical to print (as prints had to be dubbed in real time, whereas
optical could be printed at the same time and speed as the picture).   Thus,
magnetic sound fell into disuse, and is no longer commonly used, although,
before digital sound became workable, special prints were made with magnetic
tracks for showing in select theaters for 'special engagements' and the
like.

  4.4   What analog sound formats are common for 70mm release prints?

  [under construction]

     70mm                     magnetic   (?? frame offset)

    4.4.1   70mm Magnetic  (six-track stereo)

     This system is capable of carrying six separate tracks on four wide
magnetic stripes on the film.  It is usually set up to reproduce left,
left-center, center, right-center, right, and surround tracks.  This was
long considered to be the premier film-sound format, prior to the advent
of digital, because the tracks were relatively wide, because the
film runs through the projector at a slightly higher rate of linear speed
than 35mm film, and because the sound is recorded in discrete (separate)
tracks, rather than being 'matrixed.'

     As mentioned above, in the late 1970's (beginning with _Star_Wars_)
through the late 1980's, it was common for distributors to produce
70mm blowup prints of films shot on 35mm in order to improve sound re-
production in the movie theater.  With the introduction of digital systems,
which are capable of reproducing higher quality sound at a lower cost
than a complete 70mm projection system and 70mm print rental, exhibitors no
longer saw much reason to show blowup prints, except for special 'one-time'
shows.  In the future, magnetic striping (a major cost of making 70mm
prints) may be eliminated, in favor of a digital soundtrack (currently,
DTS (tm) has been used for 70mm prints).  This may encourage the printing
(and 65mm original cinematography) of more films for 70mm exhibition.

     Unlike other formats, where the soundtrack runs _ahead_ of the picture,
with 70mm, the sound runs _behind_ the picture, as the magnetic sound heads
are placed _before_ the picture head.  Thus, the 70mm print runs through
the magnetic soundhead, picture head, then around the 35mm optical soundhead,
then to the takeup reel or platter.  When 35mm films are run in a combination
projector, they are simply loaded through the 70mm magnetic soundhead,
without difficulty.

  4.5   What are the three commonly used digital sound formats for 35mm
        release prints, and how do they work?

    4.5.1   General Information

     Digital Theater Sound        (DTS) (tm)
     Sony Dynamic Digital Stereo  (SDDS) (tm)
     Dolby (tm) Digital           (SR-D) (tm)

     Digital sound differs from analog sound in that it represents sound by
a series of consecutive 'samples' of the sound (each of which is represented
by the digits zero [0] and one [1]), rather than by a continuous waveform.
Digital is neither inherently better nor inherently worse than analog, but
simply a different method of representing sound (music, dialogue, etc.).  In
practice, though, digital film sound almost always sounds cleaner and
brighter than analog, and is capable of greater dynamic range, due to the
limitations of the optical track as a means of recording sound.

     Despite the differences among the various digital sound formats, most
people cannot tell a difference in quality, as they all sound excellent.
Perceived differences among the formats are usually a result of a different
sound mix for each format (such as an 8-channel SDDS (tm) mix versus a
six-channel SR-D (tm) mix).

    4.5.2   Digital Theater Sound (DTS) (tm)

     This was the first digital sound system to come into widespread usage,
with the release of _Jurassic_Park_ in 1993.  The system was promoted
heavily by MCA/Universal Pictures, which uses it on most of its prints.  The
system originally was sold in two versions:  a low-end version which could
reproduce four tracks, and a high-end version capable of reproducing six-
tracks (left, center, right, left-surround, right-surround, and subwoofer.
These systems were referred to as DTS-4 (tm) and DTS-6 (tm), respectively.
The four-track version has since been discontinued.

     DTS (tm) uses a timecode printed on the film between the picture area
and the optical track.  The timecode is read by an optical reader placed in
the film path, between the platter or reel and the projector's picture head.
This timecode information is fed to a specialized, souped-up 386 or 486
computer which in turn reads compressed soundtracks from a CD-ROM disk; the
compression factor, though, is the least of the three digital systems.  The
current systems have three separate CD-ROM drives:  one holds a 'trailer'
disk which is sent to theaters periodically, and contains the soundtracks to
all of the trailers currently showing, including trailers from studios which
do not use DTS (tm) for their films (such as Disney); the other two contain
disks for the feature.  Shorter movies require only one disk; others require
two.  Over four hours of digital sound can be accommodated for a two-disk
feature.

     As with all digital sound systems, the film reader can be placed a
variable number of frames ahead of the picture head.  This is calibrated
upon installation with a test film.  The computer is capable of accommodating
splices within the film, and adjusting the soundtrack to match.  Further,
because the soundtrack is not on the film, no 'popping' noise is heard
during splices and/or changeovers (unless the timecode reader cannot read
a certain section of timecode, in which case it reverts back to the standard
analog track, causing a small 'pop').

     DTS (tm) is the least expensive of the various digital systems, costing
roughly $5-6000 to upgrade an existing analog system, as its outputs feed  
directly into the 'optical input' of a standard processor.  Newer versions
also have outputs for all-digital cinema processors.  All prints (except
70mm DTS prints) contain a standard optical track (usually recorded in 'DTS
Stereo (tm),' a system which is compatible with Dolby (tm)-type processors)
as a backup, should the timecode not be found, or be unreadable for more
than 40 frames.  The analog track is also used when the CD-ROM disk does
not match with the movie being shown (at least in theory--there have been
reports of showing one movie with another's soundtrack).

     Because of its low price, relative simplicity, reasonable degree of
reliability, and potential adaptability to other formats (such as the
proposed 2.5-perf prints and 70mm prints) DTS (tm) is likely to survive for
quite a while, although many theaters have had difficulty in ensuring that the
disks are shipped with the prints, as the disks are small and easily lost
or forgotten.  In such cases, the film is, of course, shown in analog, or
possibly one of the other digital formats, until the proper disks are
shipped from DTS or the distributor.

    4.5.3   Sony Dynamic Digital Stereo (SDDS) (tm)

     Sony has entered the cinema sound market with the SDDS (tm) system, used
commonly on prints from Columbia Pictures and Tristar Pictures, both of
which it owns.  Unlike the other two digital systems, SDDS (tm) is capable of
reproducing eight tracks of sound (left, center, right, left-center, right-
center, left-surround, right-surround, and subwoofer), potentially a great
advantage for films mixed for eight tracks, as an certain number are at
present.  This, of course, requires that theaters install additional
loudspeakers (left-center and right-center) behind the screen in order
to take advantage of the potential of this format, however.

     In SDDS (tm), the sound is actually recorded on the film itself, near
both edges of the print.  SDDS (tm) uses the middle degree of compression of
the digital information of the three systems.  Like the other digital systems
the reader (which uses an LED to shine through the track) is placed
somewhere in the film path prior to the film's entrance into the
picture head (the offset is variable, as convenience dictates, and is
set up at installation).  The reader reads the track, which is then decoded,
decompressed, and processed in a separate processor unit, which contains
custom electronics designed for this purpose.  Just as with analog sound,
splices are accommodated without difficulty.

     SDDS (tm) is probably the most expensive of the three digital formats,
although actual cost varies substantially among different theaters and
chains.  The expense is largely due to the fact that all of the electronics
within the entire processing system are digital, whereas DTS (tm) and SR-D 
(tm) are both designed to simply be plugged into existing analog Dolby (tm)
(or similar) Cinema Processors.  However, the extra cost is somewhat justified
by the extra tracks and the fact that the marketer of this system also owns
companies which produce many films each year, almost ensuring that there
will be material in this format for many years to come.  All prints will
also contain a standard optical track, which may be more critical than for
DTS (tm), as the edge of the film where the SDDS (tm) track is located is
often damaged by the 'white out' or shoe polish that some projectionists put
on the film to mark reel changes.  This is considered to be bad projection
practice, but it does happen quite often.

     Although it is expensive, SDDS (tm) is very popular, particularly in the
AMC, Sony, and United Artists theaters, where SDDS (tm) is or will be used
in most of the theaters.  Many technicians like it because it is the only
system with electronic equalization, allowing the system to be properly set
up very quickly.  On the other hand, there have been complaints that the
SDDS (tm) equipment is of low-grade construction, and is not particularly
reliable.  Hopefully, these problems will be addressed shortly.

     4.5.4   Dolby (tm) Spectral Recording Digital (SR-D) (tm)

     From the people who brought you Dolby Stereo (tm) comes this sound-on-
film digital system.  Like DTS (tm), it is capable of reproducing six tracks
(left, center, right, left-surround, right-surround, and subwoofer), which are
read by a reader (which works much like a TV/video camera, capturing
images of the track) placed before the picture head.  Like the other two
systems, the offset can be varied, and is calibrated at installation.

     The actual digital sound information is printed on the film in between
the perforations, generally considered to be a safer location for the
sound information than the edge of the film (where SDDS's (tm) track lives).
Thus, Dolby (tm) Digital is potentially more reliable than SDDS (tm),
although it compresses the digital information to a lesser extent than SDDS
(tm) does.  Like SDDS (tm), the track is read, and then decoded, de-
compressed, and processed by a separate unit.  Splices create small 'pops,'
but are not nearly as noticeable as with analog optical sound.

     Dolby (tm) Digital is the mid-priced model of digital sound, costing
just under $10,000 for an upgrade of an existing analog setup.  The format
appears to be increasing in popularity at this time, both in terms of the
number of theaters installing the system and the number of prints available
in that format.  It is also considered to be slightly more reliable than
the other two digital formats, as the sound is printed directly onto the
film in a relatively 'protected' location.  All prints still contain an
analog optical track (usually recorded in Dolby (tm) SR), in case the digital
system fails, or is unable to read five consecutive 'blocks' (between
perforations).

  4.6   Which studios use which formats for digital sound?

  [under construction]

     DTS (tm)   MCA/Universal (exclusively)
                20th Century Fox (some)

     SR-D (tm)  Disney/Buena Vista/et al. (exclusively)
                20th Century Fox (most)
                Warner Brothers (??)

     SDDS (tm)  Columbia/Tristar (exclusively)

     Technically, it is possible to, with minimal cost, print all three
types of digital track (or, in the case of DTS (tm), timecode), along with 
analog optical Dolby (tm) on a single print, and a few films have been
printed this way.  These multi-format prints are now quite common (containing
at least two formats).  Similarly, it is possible to have a projection system
which can accommodate all of these formats, without excessive difficulty.

  4.7   What methods have been used for digital sound in formats other
        than 35mm?

  [under construction]

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                                END OF FAQ PART 2
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