LINEAR PREDICTION IN TELEVISION 773 



Therefore, indefinite extension of this straight Hne contour deleting 

 philosophy is not a paying means of prediction, at least not at the present 

 state of the art of wide band delay lines. Furthermore, the increasing 

 diameter of the circle for extension of circular prediction would decrease 

 its accuracy for finely concentrated detail. 



Fig. 10 shows the relative position of picture elements nearest >So.o 

 if a mde band field delay were available. The methods of prediction dis- 



0,1 



;- INTERLACED FIELD 



1,0 



.1. 



Fig. 10 — Small portion of television raster showing signal samples, including 

 those of previous field, which would enable time extrapolation-space interpolation 

 as a method of prediction. 



cussed have been essentially an extrapolation in space; however, with a 

 field delay, interpolation in space, and extrapolation in time would also 

 be possible. 



EXPERIMENTAL CIRCUITRY 



Experunentally, those types of predictors that involve only a few 

 Nyquist intervals of delay are easiest to mechanize. Fig. 11 shows a 

 simplified schematic of a decorrelator that enables an evaluation of 

 linear prediction schemes having error signals given by e = ao,o«So.o ± 

 ai,o<Si,o ± 02,0*52,0 . This enables an evaluation of "pre\dous value" and 

 "slope" prediction. The signal is fed into a terminated delay line having 

 taps at Nyquist intervals. Each of these signals is individually attenuated 

 by the potentiometers in the cathode circuit of the cathode followers. 

 Each output is then fed to its respective polarity switch. The D.P.D.T, 

 switch determines to which side of the differential amplifier, F4 , the 

 particular signal is sent. Since more than one signal may require the 

 same polarity, the signals are combined through "L" type resistance 

 attenuators to prevent interaction between signals. The D.P.D.T. 

 s^^itches are so arranged that the other signals are unaffected when a 

 polarity switch is reversed. The differential amplifier, Vn , is a cathode 

 coupled circuit having the advantage of two identical grids which pro- 

 duce opposing effects in the output. The output is then matched to the 

 line by the cathode follower, Vf, . In this way we can transmit (1) the 



