the first embodiment of the invention operation s 202 is to detect a color synchronization signal of the analog video signal and the flow goes to the operation s 203 after the color synchronization signal of the analog video signal is detected operation s 203 is to detect an audio flag reference level preferably since the audio flag reference level is output after a predetermined period of time after the color synchronization signal is detected and before the audio data are superimposed in the first embodiment of the invention the receiver can determine the first detected level after a predetermined period of time as the audio flag reference level upon detection of the color synchronization signal of the analog video signal in the embodiment of the invention operation s 204 is to judge whether each row is an active row in which audio sampling values are superimposed here in the embodiment of the invention an active row can be determined from the detected audio flag reference level i e the first level detected after the period of time corresponding to the start interval of time of the audio signal after the color synchronization signal of the analog video signal is detected here an active row can be determined preferably as follows in.