GB928730A

GB928730A - Improvements in and relating to the conversion of television signals from one standard to another

Info

Publication number: GB928730A
Application number: GB4416760A
Authority: GB
Inventors: Peter Rainger
Original assignee: British Broadcasting Corp
Current assignee: British Broadcasting Corp
Priority date: 1960-12-22
Filing date: 1960-12-22
Publication date: 1963-06-12

Abstract

928,730. Television, distributers. BRITISH BROADCASTING CORPORATION. Nov. 28, 1961 [Dec. 22, 1960], No. 44167/60. Class 40 (3). Apparatus for generating from an input television signal an output signal of a different line frequency or phase comprises a plurality of storage means (for example low-pass filters or delay lines) equal in number to the number of picture elements into which a scanning line is to be resolved, a first switch operated to scan all the storage means in succession at a line repetition frequency equal to that of the input signal and to apply to each storage means a voltage or current representative of the amplitude of the input signal at the time of scanning, and a second switch operated to scan all the storage means in succession at a line repetition frequency equal to that of the required output signal and to apply to an output terminal at the time of scanning a voltage or current representative of the voltage or current in the storage means at the time of scanning. The embodiment shown is for converting from 625 to 405 lines and thus comprises 600 low-pass filters 35 which have a sin<SP>2</SP># time response although filters possessing a sin #/# or a linear time response are also said to be suitable (Fig. 3, not shown). For convenience both the first and second switch means comprise a plurality of switching elements connected in cascade. Thus the first switch means comprises the pulse generator 28, 18 diode bridges 28 and 600 transistors 34 while the second switch means comprises a similar arrangement of generator 38, bridges 40 and transistors 36. The synchronisation pulses are separated from the video input signal by the separator 27 and are used to trigger pulse generators 28, 38. Each of these produces two pulse trains x 1 , y 1 and y 2 , y 2 the phase and frequency of these being such as to switch the switching elements previously described in the correct sequence.