| 摘要 |
PURPOSE:To output a video signal and an audio signal in an optimum state by applying spread spectrum modulation to an audio signal only at recording and applying inverse spread spectrum demodulation at reproduction in a video signal recording and reproducing device. CONSTITUTION:A waveform is shaped for an audio signal by an emphasis and a filter in an audio processing circuit 23. Then frequency modulation is applied around carriers f1,f2 corresponding to L and R signals as shown in figure iii in a frequency modulation circuit 24. The spectrum of the carriers f1,f2 changes from the spectrum as shown in the figure iii into the spectrum as shown in figure iv with wider band but smaller amplitude by means of the direct spread system using PN codes outputted from a PN code generator 25. The changed spectrum shows a distribution symmetrical to the left and right around the carriers f1i and f2ii before the spread. The signal at the reproduction is discriminated into a luminance FM4 signal and an SS-FM audio signal and they are demodulated into the luminance signal and the audio signal with an excellent S/N. |
