Patent GB-1145926-A (GB)
Title: Subtitling apparatus for television transmission
Inventor: BRABON ROGER
IPC: H04N5/278
Filed: 1966-09-08
Abstract: 1,145,926. Television. ATELIERS DE CONSTRUCTIONS ELECTRIQUES DE CHARLEROI. 8 Sept., 1966 [9 Sept., 1965], No. 40199/66. Heading H4F. In an apparatus for adding subtitles to a television transmission the subtitles are printed on a paper support 1, Fig. 2, which is folded in zig-zag fashion and transferred from a first storage compartment 13 to a second 14 under the control of a stepping motor 10 which drives a sprocket 8 engaging holes in the edges of the paper. The titles are presented to a vidicon camera 7 through an apertured mask 17, the video signals from the camera passing through a camera control circuit 23 and a chain of amplifiers 24, 28, 35 to a mixer 41 where they are combined with the normal television signals. The subtitles are printed in lines across support 1 and equally spaced one after another in a column. The titles may be of varying length and occupy one or two lines. Motor 10 is energized each time a new title is to be presented to camera 7. The operation is controlled by a unit 31 which renders transmissive amplifier 28 (which is in the form of a gate amplifier) for the desired period of transmission of a subtitle and at the completion of the period produces a pulse on lead 59 to cause motor 10 to advance the next subtitle into position. Activation of unit 31 is for the period of a pulse of 5 kc/s. oscillation originating from an oscillator 50. With a switch 52 in the position shown the whole operation may be controlled manually by a push-button 54. With the switch in the lower position the operation may be controlled wholly automatically by a timer 51 which responds to the subtitle video signal from the output of amplifier 28 and (within a manually adjustable period of 1-5 seconds) controls oscillator 50 and hence also unit 31 for a period appropriate to the length of the subtitle whether or not it is one or two lines long. By appropriate operation of switches 55-57 the operation may be made either direct or indirect by way of an intermediate magnetic recording and play back of the 5 kc/s. signals. Amplifier 28, apart from being controlled to pass the subtitle signal for a desired period, also functions to " clean up " the camera signal by: (1) eliminating the synchronizing component, (2) clamping to a D.C. reference level, (3) blanking except during periods determined by the synchronizing signal which embrace the subtitle, (4) clipping at black and white levels and (5) reinsertion of the synchronizing component. The mixing stage 41 uses the subtitle video signal to blank the normal picture signal and then inserts the subtitle signal in the white direction with a 0À2 Ásec. delay. The result, which is illustrated in Fig. 54, where 110 denotes the normal video signal, 113, 116 the blanking and 114, 115 the inserted subtitle signal, is to produce the subtitle letters in white with narrow left-hand edges of black. In an alternative method of operation, Fig. 54<SP>1</SP>, the relationship between the blanking and inserted signal may be such as to produce white letters with black at both the left- and right-hand edges. Letters with black at only the right-hand edges may be produced. Also, by dispensing with the insertion signal and using only blanking, the subtitle may appear in wholly black letters. The apparatus includes picture monitors 38, 46 and an oscilloscope 49 which may be brought into use by operation of switches 26. Detailed transistor circuits for carrying out the invention together with waveforms illustrating the operation of the circuits are described with reference to Figs. 4-53 and 55-57.