A method of recording visual information such as words of a song in an audio recording medium and reproducing the same is provided. Picture information obtained through a TV camera is quantized into pulse signals. Using these pulse signals, a sine wave signal having an audio frequency band is modulated....http://www.google.com.hk/patents/US4519008?utm_source=gb-gplus-share專利 US4519008 - Method of recording and reproducing visual information in audio recording medium and audio recording medium recorded with visual information
