| 摘要 |
PURPOSE:To increase the apparent number of quantization bits of a PCM and to improve the S/N by using together both a pulse code modulation PCM recording system having a small number of quantization bits and a frequency modulation FM recording system. CONSTITUTION:For a PCM system, the quantization is performed with about 8 bits as conventional and then the recording is carried out after signal processing. While an A/D converter 4 converts the digital quantity which is quantized by an A/D converter 2 into the analog quantity. A subtraction is performed by a subtraction circuit 5 between the value converted into the analog quantity by the converter 4 and the original signal value to obtain an error of quantization. This error is held and only the sound signal band is extracted through an LPF7 in the form of a PAM (pulse amplitude modulation) wave. This PAM wave is superposed on a video signal after FM modulation performed by an FM modulation circuit 8 and then recorded to a video track. In this case, the error of quantization is set at 1LSB (least significant bit) and then the 100% modulation is set equal to 1LSB in order to improve the S/N. |
