GB2094537A - Multi channel sound/data track layout - Google Patents

Abstract

This layout is principally intended to be applied to motion picture film but is equally applicable to television and other devices by which digital or analog sound, data and pictures may be electrically, mechanically or optically recorded and reproduced. A film recorded with this layout can be reproduced monophonically by any standard photographic sound head, without alteration, in the same way as a normal photographic soundtrack. Magnetic striping is envisaged. This invention confines itself to the layout of the tracks to present a compatible format and does not deal with the methods of recording and reproduction. <IMAGE>

Description

SPECIFICATION Multi channel sound/data track layout Background of the invention This invention relates to sound systems and in particular to a new and improved compatible mono/stereo photographic sound system especially suited for use with motion picture theatres with data control.

Stereophonic sound systems have been known for many years. British Patent to Blumlein, No.

394,325 discloses most of the significant features and two channel systems have been used extensively since about 1 958. A multichannel sound system was used in the motion picture field for the film, Fantasia. This system was extremely complex and expensive and has not been used since the 1 939 production. In 1953, CinemaScope with four magnetic tracks striped on the motion picture film and a large screen were introduced. Four soundtracks were recorded on the film, with three of the sound channels positioned behind the screen at the left, center and right, with the fourth channel sometimes referred to as a surround track. This fourth channel fed a plurality of speakers positioned at the sides and back of the theatre with all speakers connected together. The fourth track was switched on to produce a dramatic effect when desired.A later variation utilized six magnetic tracks on the film with five speakers behind the screen, with the sixth track used to drive the speakers at the sides and back of the area. None of these configurations have been particularly satisfactory because of their added cost both in making the special prints and maintaining the complex theatre systems compared to the standard photographic single channel soundtrack.

In order to maximize the use of 35mm prints, magnetically striped and recorded for 4 channel stereophonic sound, the monophonic photographic sound track has been added, thereby making a compatible print. But as aforesaid, this process is seldom used because of its cost. In recent years there has been a renewed interest in multi-channel stereophonic sound for motion picture films and television. Since the photographic soundtrack is applied and processed simultaneously with the picture, there are obvious advantages to be had to confining film sound to this format. Throughout the history of sound on film covering the last 50 years, many photographic formats have been used, covering both the sound itself and means of controlling it.

Both single ended and push-pull systems have been used. Since about 1938, all films released for normal theatrical exhibition have had their soundtrack made to conform to the "Academy Curve". This was fully described by the Motion Picture Research Council in their publication entitled, "Standard Electrical Characteristics for Theater Sound Systems", dated April 20, 1948.

This curve was derived empirically to give the best compromise between signal to noise ratio, dynamic range and frequency response. It is shown as Figure 1 hereof. It will be appreciated that this curve is a far cry from the modern ideal of a wide range system. Furthermore, in order to obtain satisfactory sound in the theatres, the recordings are made with considerable upper mid-range and high frequency pre-emphasis.

Despite numerous attempts to circumvent the Academy Curve, no commercial system exists. It must be understood that of the 85,000 theatres situated in the Western world, less than 10% are able to reproduce anything other than the Academy Curve. A key part of this invention is the inclusion of an "Academy Track" situated in such a way that whenever a film recorded in accordance with this invention is placed upon a standard "Academy reproducer", it will be virtually indistinguishable from the same material recorded with a standard optical recorder.

Sinultaneously the soundtrack described in this invention contains a minimum of four additional soundtracks for stereophonic sound plus extra tracks for data, automatic switching and guidance. By using a suitable data system such as the SMPTE time code, useful information and commands can be stored on a per frame basis.

Summary of the invention The multi-purpose sound/data system of the present invention in the prefaced embodiment incorporates an "Academy" monophonic variable area recording, a minimum of 4 constant width wide range sterophonic recordings to be reproduced as left, center, right and surround channels, a data track and an additional locator track to aid in the guidance and scaling of the system when it is reproduced stereophonically. It is a feature of this invention that the tracks fall within- the area assigned by existing American National Standards and their ISO counterparts.

Furthermore, an important feature of this invention is its compatibility with all existing photographic reproducers so that when a recording is reproduced, it will be virtually indistinguishable from a normally recorded monophonic Academy track. No data will be heard and there will be no discernable cross-talk from the stereophonic channels on a reproducer conforming to the established standards and recommended practice. This is because a normal photo-optical system recognizes changes in light level to produce an electrical output. Therefore no modulated output will be derived from lines of constant width.

This invention distinguishes itseif from other systems that have proposed a similar combination track using modulated locator channels placed at the extremities of the projector scan. The use of such tracks are not practical since they produce cross-talk into an Academy reproducer and their data handling capacity is significantly inferior to the preferred embodiment of this invention.

Figure 2 shows the preferred track layout for this recording system and the relationships of the standards for reproducing and printing of photographic sound tracks. By placing the Acedemy track as shown, not only will it be properly reproducible under the described conditions, but the print may be magnetically striped in accordance with ANSI PH 22.177. The remaining half of the normal projector scan will view the left, center and right stereophonic tracks in the preferred embodiment.

By placing the surround track outside the normal projector scan, it can be recorded with a compound signal like a stereophonic phonograph record groove, thereby embodying 2 or more separate channels of information. The MS technique is described in British Patent 394, 325 and a 4-2-4 channel system is described in U.S.

Patent 3,787,622. When properly recorded, the surround track can be reproduced compatibly as 1, 2 or 4 channels of sound, depending upon the sophistication of the reproducer. A compound signal cannot be placed inside the normal projector scan since it would contribute unacceptable cross-talk into the Academy reproducer when the film is played monophonically. If preferred, a multiciplicity of separate tracks can be used to accomplish this end.

The preferred data command track of this invention is the SMPTE time code, which is in extensive use in the television field. Since each frame of picture is uniquely identified, it offers an easy method of timing, editing and assembling programs.

The application of this system to motion picture photography can result in similar advantages since the "Manchester Codes" (as embodied by SMPTE) have considerable unused spaces which can be user assigned. These spaces are of enormous potential value for control of the projection equipment, theatre lights, curtains and special effects from the recording. Also multilingual captioning data can be incorporated into the same spaces. These data can be presented with an alpha numeric device or preferably pin diode or similar arrays of suitabie dimensions through an appropriate decoder under the screen. Pin diode arrays permit any language or diagram to be embodied into the data, thereby making a single recording usuable world wide.

It is a desirable feature of this invention to incorporate an additional reference track within the recording so that the stereophonic reader will be able to recognize the track format and provide both proper scaling and electronic guidance of the reproducer. U.S. Patent 4, 124, 784 describes such a reproducer. Since a normal photographic soundtrack reproducer is a relatively crude mechanical device, producing mechanical jump or weave, special guidance is mandatory in order to ensure lack of cross-talk and distortion. Although the placement of this locator track is relatively unimportant provided it is unmodulated, it is ideally placed at the opposite extremity to the command track in order to provide the maximum mechanical advantage or fuicrum.

Whilst the preferred embodiment contemplates a 7 track photographic recording with a motion picture film, it is readily appreciated that more sound sources and channels can be utilized and that other recording and reproducing media can be used. Figure 2 shows how this system can be incorporated into 35mm film, but it can easily be applied to other gauges embodying more or less channels whilst retaining compatibility and the other advantages of this invention.

The system of the present invention is compatible with presently available equipment including microphones and speaker, encoders and decoders, and film recording and projection equipment. A specially designed multitrack recorder is the preferred means of laying down the multiple tracks. For example, a cathode ray tube is an excellent modulator. Also, standard faders, noise reduction systems, amplifiers, mixers, limiters, compressors, panpots and other signal modifying means may be utilized as desired. When desired, the system of the present invention can be installed in conjunction with existing sound systems with appropriate switches for selecting one system or the other depending upon the theatre operators' desires.

Claims (12)

Claims

1. A photographic motion picture soundtrack conforming to established recording, printing and reproducing standards being a combination of: a variable area monophonic recording contained between 244 and 286 milli-inches from the reference edge of 35mm film intended to be reproduced through a standard academy photographic soundhead; three constant width high quality sound tracks contained between 202 and 244 milli-inches from the reference edge of 35mm film intended for left, center and right channel reproduction through a special soundhead; an additional high quality combination track containing a multiplicity of tracks or one directly recorded constant width or matrix encoded variable width recording to be reproduced as single or multiple channel surround tracks through a special soundhead.This track will be placed at 290 milli-inches or more from the reference edge of 35mm film to avoid cross-talk into the Academy scan area; a command data track placed between the perforations and 200 mill-inches from the reference edge of 35mm film. This track is to be used separately or in conjunction with the locator track to identify, turn on, scale and follow the multiple tracks, command the projector, theatre equipment and special effects as required and provide data for display of captions and diagrams; an unmodulated locator track placed at the opposite extremity of the multiple tracks from the command track to be used separately or in conjunction with the command track to verify, turn on, scale and follow the multiple tracks.

2. A system as defined in Claim 1 where a multitude of variable area or variable density recording are used for Academy reproduction.

3. A system as defined in Claim 2 which incorporates a single composite command track.

4. A system as defined in claim 2 which can be magnetically striped for mag-optical reproduction whilst retaining the Academy monophonic information for optical reproduction.

5. A system as defined in Claim 2 where a second command track is used in place of the locator.

6. A system as defined in Claim 2 where the unmodulated locator track is placed on the edge of or inside the Academy scan.

7. A method as described in Claim 2 whereby a visual image is combined on the same piece of film that contains the tracks to which it bears a synchronous relationship.

8. A method as described in Claim 7 whereby the process is applied to other gauges of motion picture film using more or less tracks as befits the film.

9. A method as described in Claim 8 whereby the combination sound and data tracks are recorded on and reproduced from other media whereby such signals can be electronically, mechanically or optically stored.

10. A method as described in Claim 9 whereby a signal containing monophonic, stereophonic and data handling capability are combined in a single composite track.

11. A method as described in Claim 10 whereby a picture is combined with the composite track.

12. A method as described in the above claims whereby the order of the tracks is interchanged.