Audio signal processing
As we saw earlier in this chapter, the ingredients for success in recording TV pictures on tape are high writing speed and FM modulation. Within the immovable constraints of existing formats, it was obvious that for better sound performance these virtues must also be applied to the audio
signal. The obvious solution was to record an FM-modulated sound car- rier in or around the helical video tape tracks; but with the vision heads and tracks already chock-full of information, the problem was where to squeeze in the audio recording with regard to frequency-spectrum space and the ‘magnetic’ capacity of the tape track. Some form of multiplex system is required. Two alternative systems emerged for home VCR formats—depth multiplex, used in VHS models; and frequency multiplex in Video-8 format. The former is the most common, and will be covered first.
