Patent GB-1275790-A (GB)
Title: Improvements relating to video signal recording
Inventor: GOLDMARK P C
IPC: H04N5/84
Filed: 1969-11-14
Abstract: 1275790 Recording video information COLUMBIA BROADCASTING SYSTEM Inc 14 Nov 1969 [15 Nov 1968] 55917/69 Heading H4F Video information for reproduction by television scanning techniques is recorded on a monochrome record medium 10 carrying two longitudinal successions of frames 12, 14 arranged alongside one another in pairs, each frame carrying a monochrome representation of video information, synchronizing marks 20 being associated with each pair of frames in the same longitudinal relation to the frames in each case so as to produce a vertical synchronizing signal upon reproduction of the recorded information. The two frame successions may carry independent monochrome programmes, but in the preferred form shown the right hand frames 12 carry luminance data (i.e. a monochrome picture) while the left-hand frames 14 carry corresponding colour information coded into monochrome bands. Magnetic or optical sound recording strips 18 are provided at the edges of the medium 10. The record medium 10 may be used to record taped or live video programmes, but the Specification is mainly concerned with apparatus for recording a colour video programme from a cinematograph film original. The recording is carried out by means of a scanned electron beam recorder 30, the intermittent film feed of which is synchronized with that of the original film projector 28 in such a way as to convert the original 24 frames/sec. standard into the desired 50 or 60 frames/sec. television standard. This is achieved by double and/or triple recording of each original frame. A rotating shutter 31 situated between the projector 28 and the four vidicon t.v. camera chain 26 viewing it interrupts the projected scene while the film is being advanced and thereby prevents image-blurring. The colour video signal is separated into luminance and colour components, and the former component is subjected to vertical aperture equalization at 48, the latter being encoded at 50. The encoder circuit 50 output comprises a compositive signal containing a pilot carrier signal as well as a colour carrier signal modulated in amplitude and phase in accordance with the original colour saturation and hue. Both carrier signal frequencies are multiples of the line recording rate, and since narrow blanking terminating before the beginning of each line of video information is applied in the encoder 50 each line is preceded by several cycles of the pilot signal alone. This results in the provision of a strip 21 on the recording medium 10. An electronic switch 66 alternately supplies luminance and colour signals to a blacklevel clamp 72 and hence to a mixer 74, whereby the recorder 30 scans first the left-hand and then the right-hand frame of each pair before proceeding to the next pair. If independent monochrome programmes are being recorded a switch 70 is operated successively in the two "mode 2" positions. In the mixer 74 the synchronizing reference signal which will result in formation of the synchronizing marks 20 on the recording medium is added to the video signal. The reference signal is derived from a sync. generator 29 via a first channel including a vertical height multivibrator 87 whose output is a pulse at the frame frequency having a duration corresponding to the number of horizontal scanning lines to be used in recording the mark 20, and a second channel including a horizontal gate pulse generator 90 at the line rate initiated upon termination of a narrow blanking signal applied thereto, the second channel fixing the transverse location and dimension of the mark 20. Horizontal aperture equalization is applied to the combined signal at 76, the signal then being supplied to the recorder 30 via a gamma amplifier 78. Since all the colour information is stored in monochrome form no colour deterioration of the recording medium 10 can occur and, furthermore, deficiencies in the colour of the original film may be removed in the processing.