Patent GB-1419267-A (GB)
Title: Method of recording a three-line sequential colour picture signal
IPC: H04N9/86
Filed: 1972-11-20
Abstract: 1419267 Television TED BILDPLATTEN AG AEG TELEFUNKEN TELDEC 20 Nov 1972 [19 Nov 1971 9 Dec 1971] 53570/72 Heading H4F To enable a luminance signal formed during playback of a three colour line sequential recording by the addition of equal amounts (33) of the recorded colour signals, to correspond to the standard luminance signal .59G+.30R+ .11B, the original colour signals R, G, B are each modified by the addition of a signal (Z = .26G - .03R - .22B) derived from the original colour signals and the modified colour signals used for the recording and the formation of the luminance signal. In the embodiment of Fig. 1 the simultaneous colour signals R, G, B with bandwidths of 0 - 2 MH 3  are converted into a line sequential signal 5 by line switch 4 for application to adding stage 6, and in matrix 7, to the standard form luminance signal, .59G+.30R+.11B, which signal then has its bandwidth limited at 21 to .5 - 2 MH 3 . The simultaneous signals are also converted in a matrix comprising weighting stages 18, 19, 20 and adding stage 22, into the modifying signal Z = .26G - .03R - .22B which signal is fed to the other input of adding stage 6. The modified colour signals have their bandwidths limited to 0 - .5 MH 3  at 12 and are combined in adding stage 9 with the standard luminance signal Y H  for recording at 13. In the reproducing apparatus, Fig. 4, the standard luminance signal Y H  (.5 - 2 MH 3 ) is extracted from the recorded signal at 24 and fed to an output combining stage 25. The modified line sequential colour signals R* = R + Z, G* = G + Z and B* = B + Z are extracted at 23 and modulated on to a carrier at 26. Two line delays 28, 29 and switch 30, enable the conversion of the line sequential signals into simultaneous signals: F G *, F B * and F R *. If the modified colour signals are added in equal amount (.33), using the delays 28, 29 and adding stage 33. a luminance signal F YM  is produced with a bandwidth 0 - .5 MH 3  where: F YM =.33(F G * + F R * + F B *)=.33(F G  + F R + F B ) + F Z =F G (.33 + .26) + F R (.33-.03)+ F B (.33-.22)=.59F G +.30F R +.11F B . This is the standard luminance signal, which after demodulation at 34 is combined as Y M  at 25 with the luminal signal Y H , to give an output luminance signal with a full bandwidth 0-2 MH 3 . The simultaneous signals from switch 30 are combined in matrix 35 to give colour difference signals F* B  -  Y , F* R  -  Y  where: F* B-Y =F B *-F Y =(F B  + F Z )-(F Y  + F Z )= F B - F Y =F B - Y . F* R-Y =F* R  - F* Y  + (F R +F Z ) -(F Y +F Z )-(F Y +F Z )=F R -F Y =F R-Y . The colour difference signals F B-Y , F R-Y  are quadrature modulated by alternating phase shifter 36 according to the PAL standard, and combined at 25 with the luminance signal. In the arrangement of Fig. 2 a luminance signal Y M  from matrix 10 = .33 (G+R+B) is subtracted from each of the colour signals to give, in combination with a low pass filter 12 partly modified signals R - Y M , G - Y M , B - Y M , extending over the bandwidth 0 - .5 MH 3 . A standard luminance signal Y= .59G+.3R+.11B is produced by a matrix 7, extending over a bandwidth 0 - 2 MH 3 . The partly modified signals and the luminance signal are combined at 9, such that over the bandwidth 0 - .5 MH 3  the signals which are recorded are: G-.33(G+R+B)+.59G+.3R+.111B=G+Z R-.33(G+R+B)+.59G+.3R+.11B=R+Z B-.33(G+R+B)+.59G+.3R+.11B=B+Z whilst over the bandwidth .5 - 2 MH 3  the luminance signal Y=.59G+.3R+.11B is recoded. This is the same as in Fig. 1. A feedback arrangement may be used to keep the amplitudes of the various signals under control (Fig. 3, not shown).