AP mast (2K)


by Arthur Dungate


The AP Film Dubbing Suite

This was situated on the ground floor, replacing the original 'cinema' alongside the sound transmitter and Baird's vision transmitter hall.


When the BBC decided in 1948 to make its own newsreel for the Television Service it was realised that an in-house facility would be advantageous. Until the AP Dubbing Theatre came into service at the end of 1949 the Television Newsreel (TNR) was recorded and dubbed in the Re-recording Theatre of RCA situated in The Tower, at Hammersmith Broadway.

N.F.Chapman, of Planning and Installation Dept (P&ID), BBC Engineering Division, published a technical description of the new facilities at AP in ???


A Film Production Unit is an essential part of a Television Service. One of the most important functions of the B.B.C. Film Unit is the regular production of newsreels, but its activities cover a wide field and include the production of film sequences for television plays and special documentary and demonstration films.

In addition, the unit is responsible for editing “Telefilms” and for checking and preparing such commercial films as can be obtained for television. To enable these activities to be carried out efficiently, and to ensure that the productions shall attain a high standard of technical excellence, a comprehensive scheme for equipping the Film Unit with apparatus of the latest design and best obtainable performance has been prepared. This scheme is now well advanced, the first project to be completed being the film dubbing and review suite at Alexandra Palace.

Film dubbing and review theatres are, of course, used in commercial film production, and the arrangements at Alexandra Palace conform in fair degree to standard modern practice. Several features are unusual, however, and as the suite is probably one of the first to be built specifically for television film production it is hoped that a description of it will be of interest, especially to those engaged in television who are unfamiliar with modern film technique.


Film Dubbing Section
The conclusive stage in the production of a film is the making, in the laboratories, of the “married print" which carries both the edited picture and the final sound track. The recording of this final sound track entails the making of a new sound-negative by combining or mixing to-gether in one operation a number of separate sound sources both live and pre-recorded on disk and/or film, and photographing this "mixed sound" in a "sound-camera". How this is done can perhaps best be described by outlining a typical dubbing session for, say, Television Newsreel:

  1. A "rush" print of the edited picture film is projected on a screen to provide cues for the commentator and the engineer at the mixer desk.

  2. Previously prepared sound-on-film recordings which have been exactly synchronised with the picture, e.g. original dialogue, title and background music, and effects, are reproduced on separate sound-on-film machines electrically synchronised with the projector.

  3. Effects that need not be exactly synchronised with the picture, e.g. crowd and traffic noises, are reproduced from disks on gramophone turntables, which are so placed that the operator can see the screen.

  4. A commentator reads before a microphone a previously prepared script when cued by the film editor who watches the screen.

  5. A sound-mixer combines and balances all the above-mentioned sound sources at a mixer desk facing the screen.

  6. The combined sound output from the mixer desk is recorded photographically on a separate film running in synchronism with the projector and the sound-on-film reproducing machines.

  7. Negatives of the picture and the recorded sound track are printed on to a single film to form a combined standard sound and picture film for transmission.

In addition, the film dubbing section is equipped for the carrying out of several other operations. It can be used for reviewing 16mm or 35mm films with combined or separate sound tracks, for disk to film or film to film re-recording, and for recording from any source on 35mm film running in synchronism, if necessary, with a film picture camera in the dubbing theatre or in one of the studios. It can also be used for post-synchronisation, i.e. the addition of exactly synchronised speech to a previously prepared silent film sequence, and for the addition of live commentary and non-synchronous music and effects to a silent film during transmission. Several of these operations can, as a result of the way in which the dubbing section has been designed, be carried on simultaneously.

Film Review Theatre
35mm films with combined or separate sound tracks can be projected in the review theatre. The projectors, which are similar to those installed in the dubbing section, are normally driven by synchronous motors, but Selsyn drives are fitted as well in order that the sound heads may be synchronised with the machines in the dubbing Section, so that two additional sound tracks can be used in a dubbing session if required. This arrangement also enables a maximum of four sound tracks and one picture film to be reproduced in the review theatre in synchronism without interfering with a review session in the dubbing theatre.


As has already been mentioned, film dubbing suites are a common feature of all film production centres, and the question arises, what are the particular requirements of a suite built specifically for television film production? In the present state of the art these requirements may be summarised as follows:

  1. The conditions under which sound monitoring is carried out should simulate those found in the home rather than those found in the cinema.

  2. The screen should be so proportioned that the angle it subtends at the producer"s or sound-mixer"s position is approximately equal to the angle normally subtended at the viewer"s eye by the screen of his television receiver, in order to prevent material unsuitable for a small screen from being included.

  3. Flexibility is of paramount importance:
        (a) To enable newly discovered techniques to be adopted without re-design work.
        (b) To make possible high-speed working, thereby reducing cost to a minimum and ensuring that the finished product is completely topical.
        (c) To enable the suite to deal efficiently with a continuous flow of varied sessions, or to enable a comprehensive dubbing session to take place at a moment"s notice.

  4. Reliability and interchangeability of equipment are essential. Dubbing sessions frequently precede the transmission time only by the period required for laboratory processing, so that a breakdown would result in transmission being delayed.

  5. Film shooting of at least "head and shoulder" subjects should be possible in the dubbing theatre, in order that announcement films and the like may be readily made without recourse to the use of a studio.

  6. Provision must be made for the addition of 35mm magnetic film recording as soon as it becomes available, since a recording system with direct playback is necessary in addition to the standard photographic system.

  7. 16mm projection must be provided, with arrangements for locking the projector with the 35mm equipment in the dubbing system.

  8. Television monitors must be provided at the commentary and sound mixing positions in order that live sound may be added to a film while it is being transmitted.

The general layout

First published 1999 Second edition 2002/2003..... Page created by Arthur Dungate