Department of Computer Science
University of Fribourg, Switzerland
Sylvain STOTZER
Phonographic Record Sound Extraction by Image processing
The phonographic record was the only way to store sounds until the introduction of magnetic
tape in the early 50's. Therefore there are huge collections of phonographic records, for
example in radio stations and national sound archives. Such archives include pressed discs,
which were produced in mass by record companies for commercial distribution, as well as
direct cut discs obtained by the direct recording with often a great cultural value and available
only as single copies. Many records are deteriorating with time. Worse, many records are in
an advanced stage of decay and would be destroyed by the movement of the stylus from even
the best turntables. Thus, we risk loosing an important cultural heritage, if no alternative
playback system is developed.
In record players, a needle follows the position of the groove and converts it into an electrical
signal corresponding to the sound. This means that the radial displacement of the groove
contains the sound information. Thus the sound information is visible and it is then possible to
extract it by image processing techniques. These observations lead to the VisualAudio project,
which proposes an optical system to extract the sound from phonographic records. The
VisualAudio concept proposes first to take the record in picture, in order to have a
photographic copy of the record and of the sound. This photographic sound copy can be
stored for long term archiving. Then the film is digitized using a specially designed rotating
scanner, and the image is processed in order to extract the recorded sound. Thus this system
can play records without deteriorating them and it is also able to play severely damaged
records.
This work focuses on the image processing parts of the VisualAudio project. The image
acquisition system is thoroughly studied to understand the image formation process as well as
all kinds of degradations, which may affect the final sound quality. Based on this analysis, a
groove model is proposed, in order to develop dedicated image extraction and signal
correction methods. The whole system is then evaluated to point out the strengths and
weaknesses of the VisualAudio sound extraction process.
Jury Members
Prof. Béat Hirsbrunner, University of Fribourg, Switzerland, Chairman
Prof. Rolf Ingold, University of Fribourg, Switzerland, Thesis Supervisor
Prof. Martin Vetterli, Swiss Federal Institute of Technology Lausanne (EPFL), Switzerland
Prof. Ottar Johnsen, University of Applied Sciences of Fribourg, Switzerland
Prof. Frédéric Bapst, University of Applied Sciences of Fribourg, Switzerland