Cutting a disk was in practice the only way to preserve sounds until the introduction of magnetic tape in the early 50’s. Therefore there are huge collections of phonographic records, for example in radio station and national sound archives. Such archives include pressed disks produced by record companies as well as direct cut disks obtained by the direct recording of radio programs with often a great cultural value and available only as a single copy. Disks, and in particular acetates and shellacs, are fragile. Many records would be destroyed by the movement of the stylus from even the best turntables. Worse, all the records are deteriorating with time. We risk loosing an important cultural heritage.
In record players, a needle is following the position of the groove and converts it into an electrical signal corresponding to the sound. It means that it is the radial displacement (and the depth for stereophonic and vertical cut records) of the groove that contains the sound information. It means that the sound information is contained in the image of the record. This observation leads to a technique called VisualAudio, a 3 steps concept:
1. An analog picture of each side of a disk (either 33 or 78 rpm) is shot. The film must have a high spatial resolution and be as large as possible (about 1:1), since we wish to catch the finest details of the groove. This process can be done quickly. The film is cheap, and can be stored for a long time (more than 100 years). That way, the sound information is preserved in case the original disks deteriorate.
2. When anyone wants to recover the sound, the film is scanned, using a specially designed rotating scanner, and digitized.
3. The sound must then be extracted from the digital image. This requires image processing techniques in order to extract the radial displacement of the groove (which contains the sound), to detect cuts and to correct other defects. Digital signal processing must be applied to the groove signal to extract the sound.
Was ist das Besondere an diesem Projekt?
Das innovative Forschungsvorhaben mit originellem Ausgangspunkt hat wenig kommerzielle Perspektiven, leistet aber einen sehr wichtigen Beitrag zur Archivierung alter Tonträger und damit zum Erhalt kulturellen Erbes. Mit einer Initialfinanzierung unterstützt die Gebert Rüf Stiftung das Vorhaben.
The system has been designed built and tested, in particular 1) a system to photograph phonographic records, 2) a circular scanner to digitize the films of the records. The software to extract the sound from the digitized records has also been designed, written and tested with a set of various kinds of records from audio archives.
The photography system allows us to take the picture of the records. It can be considered as finished, working according to the specifications, and is in use. We get with this system better films of the records than before. In particular, pictures are more homogeneous. We received in donation a developing machine that has been refurbished and is used in the process.
The circular scanner was designed and built. It is designed to scan the film. It uses a linear 2048 pixels sensor. It is a rotating scanner, and we digitize the film one ring after the other. It works as planned.
The software in particular the part that extracts the sound from the scanned film has been greatly improved. The improvements includes better sound extraction algorithms, as well as a more robust and user friendly front end that is ready for mass saving.
The system is working as planned, even if we would naturally hope for even better sound quality. Modeling shows that we are near the physical limits. We have started using the system for extracting the sound from the Swiss Radio archives. We are also in contact with foreign sound archives for the extraction of the sound from historically important records.
This project can be considered as a precursor. It is the first system proposed to extract the sound from the image of a record. Its relevance and vision is illustrated by the fact that now several institutions have also started ambitious projects to optically playback records, in particular Lawrence Berkeley National Laboratories, Mc Gill University, University of Southampton. It has got a large media and scientific exposure through numerous newspapers, TV and radio programs, talks given at many institutions, scientific papers, as well as numerous student projects. It has been a showcase for visitors to our school. In particular a demonstration was made to the foreign ambassadors in Switzerland accompanied by to Mr. Joseph Deiss, president of the Swiss Confederation, and Mrs Micheline Calmy-Rey, Swiss Minister for Foreign Affairs. It has made collaborations withseveral foreign institutions possible. A very successful collaboration took place between Ecole d'ingénieurs de Fribourg, Université de Fribourg, Ecole des arts appliqués de Vevey and the Phonothèque nationale Suisse. A sound archivist conference was organized in Fribourg to demonstrate the system. More exposure is expected in the future, as the system gets used to extract the sound of important historical records.
A new project has started (project GRS 046-05) for an extension of the system to very difficult records, in particular the numerous delackered records where there are cuts of several mm.
September 2006: Ph. D. thesis „Phonographic Record Sound Extraction by Image Processing“, by Sylvain Stotzer
Phonographic Sound Extraction using Photography and Signal Processing, Digital Signal Processing journal, Elsevier, to be published.
Phonographic Record Sound Extraction by Image Processing, Ph. D. thesis, Sylvain Stotzer, Université de Fribourg, to be publishedS.. Cavaglieri, O. Johnsen,
S. Stotzer, O. Johnsen, F. Bapst, C. Milan, C. Sudan, S. Cavaglieri, P. Pellizzari "VisualAudio: an Optical Technique to Save the Sound of Phonographic Records", JTS, Toronto June 2004.
S. Stotzer, O. Johnsen, F. Bapst, C. Sudan, R. Ingold, "Phonographic Sound Extraction Using Image and Signal Processing", Proceedings 2004 ICASSP, May 17-21 2004, IEEE, ISBN 0-7803-8485-7, Vol 4, pp 289-292, Montréal, 2004.
O. Johnsen, F. Bapst, C. Sudan, S. Stotzer, S. Cavaglieri, P. Pellizzari, "VisualAudio: an Optical Technique to Save the Sound of Phonographic Records", IASA Journal, No 21, June 2003.
O. Johnsen, F. Bapst, C. Sudan, S. Stotzer, S. Cavaglieri, P. Pellizzari, "VisualAudio: eine optische Technik zur Bewahrung phonographischer Aufnahmen", "Schall und Rauch", No 6, Mai 2003.
F. Bapst, "Optical Retrieval and Storage of Analog Sound Recordings", AES 20th International Conference, Budapest, 2001.
S. Stotzer, O. Johnsen, C. Sudan, F. Bapst, "VisualAudio: une technique visuelle d'extraction du son des anciens disques phono", Flash Informatique de l'EPFL, No 10, 2002.
„Archives: écoutez voir!“, Nouvo, TSR, Switzerland, 16.04.2005
„Fotografien retten alte Schallplatten“, MTW, SF DRS, Switzerland, 16.12.2004
"Den Ton von Schallplatten optisch erfassen", Universitas Friburgensis, Switzerland, 26.10.2004
"Die Rillen der Schallplatten werden zu digitalen Tönen", Nano, 3Sat, Germany, 21.10.2004
"Tecnologia dá voz ao passado", Swissinfo, Switzerland, 21.09.2004.
"Le 78-tours change de disque", article published in L’Express, France, 31.05.2004
"Klingende Bilder", article published in NZZ, Switzerland, 07.05.2004
"Les capsules multimédias", Radio RSR La Première, Switzerland, 24.02.2004 and 25.02.2004.
"Platten-Retter", article "Tele, das Schweizer Medienmagazin", 15/03, page 123, 12-18.04.2003.
"Mémoire photographique", article published in "24 heures", 7.03.2003, page 8.
"Ils prennent le son en photo", article published in "La Gruyère", 4.03.2003, page 9.
"Wertvolle Kulturgüter vor dem Zerfall retten", article published in "Tages Anzeiger", 19.02.2003, page 68, also published in "Swissinfo" le journal informatique de la confédération, 24.02.2003.
"A Fribourg, des ingénieurs ont inventé la machine à sauvegarder les disques anciens", article published in "Le Temps", 20.01.2003, p33.
"Fototermin für alte Schallplatten", article in "Der Bund", 28.11.2002, page 38.
"Des ingénieurs mettent en image des vinyles pour mieux les sauver" article in "La Liberté", 01.12.2000, page 15, also published in "CTI: courrier des professionnels de la technique et de l'informatique", numéro 4/2000, 28.12.2000.
Am Projekt beteiligte Personen
Cédric Milan, Ecole d'Ingenieurs de Fribourg, 80 Boulevard de Perolles, 1705 Fribourg, tel +41 26 429 65 78, fax +41 26 429 66 00, cedric.
Sylvain Stotzer, Ecole d'Ingenieurs de Fribourg, 80 Boulevard de Perolles, 1705 Fribourg, tel +41 26 429 66 78, fax +41 26 429 66 00, sylvain.
Letzte Aktualisierung dieser Projektdarstellung 28.07.2018