Phonographic sound extraction using image and signal processing

The optical retrieval and storage technique called VisualAudio provides a way to extract sound information from an analog disk without any mechanical contact. The process is straightforward: we take a picture of each side of the disk using a dedicated analog camera, we store the film as our working copy, and when needed, we scan the film and process the image in order to extract the sound. This technique can be used to retrieve the sound from old records that are in such a bad shape that no regular turntable can be used. A working prototype has been built and has retrieved the sound from several records. We present the signal processing issues of this system and, in particular, a signal-to-noise ratio analysis.