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Saphir : Optical Playback of Analogue Audio Disc RECORDs

Description

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From the 1930s to the end of the fifties, most audio recordings of radio stations were kept on 78rpm discs (magnetic tapes only started to be used routinely in France from 1950). Over time these records (discs) have deteriorated through handling or natural causes. Some records of priceless historical value can no longer be read by the usual means (magnetic cells with a diamond stylus) and the surface of the disk cannot be mechanically restored. Some 20,000 of INA's 276,000 discs are in such a condition. The same applies in a large number of archives of radio broadcasting organisations all over the world.

Scratched, broken or split discs cannot be played by mechanical means. This is also true of discs whose surface has altered and deteriorated.

Our process can read these discs optically, without a stylus and without any physical contact.

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Operating principle

In 2002 INA devised an innovative process (patented in 2004) for optically reading audio discs based on reflective properties of the groove walls. With the participation of INDEEP, in the framework of the PrestoSpace project, we have carried out research and designed a device that converts the signal from pictures of the disc's surface into an audio signal.

  • A camera acquires the images.
  • The sides of the groove act like mirrors angled at 45 degrees that reflect light coming from a single direction, which depends on the initially recorded signal.
  • A specially designed lighting system adjusts the colour of the flash depending on direction.
  • The grooves appear on these images as coloured lines.
  • A subsequent process translates these colors into audible signal.
  • Several tracks are digitised on each rotation of the turntable.
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Image : Claude Grill (Univ. Montpellier 2) / Camille larousse / Electron microscope view

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Principe for optical extraction of audio signal using colour

Pros and Cons

Benefits compared with mechanical reading processes:

  • No inertia: the signal is not distorted
  • No wear of the disk
  • Selecting suitable stylus not needed
  • Cleaning the disk is not so important
  • Discs covered with scratches or cracks can be read

Benefits compared with other optical reading processes:

  • No consumables (photographic film)
  • Standard camera, medium resolution
  • Detection of regions where the signal is unreliable (scratches, occultations). The signal can be reconstructed selectively in such regions.
  • Dirty discs can be read.

Drawbacks:

  • Slow: currently several hours per side
  • Quality often lower than using conventional playback. To be restricted to difficult cases (broken/cracked/de-laminated...)
  • Dirty discs can be read.

Physical implementation

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The optical scanning head, illustrating the optical paths

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Scanning through a glass pane

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Indeep / J-H Chenot (INA) Future version of the scanner

Broken discs

The retracted cellulose lacquer on these discs makes them unreadable with conventional processes.

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A cracked lacquer disc record, recorded 04/03/1942

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The different patches of lacquer

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Close-up of the connections between four patches, with needed connections

Decoding interfaces

A dedicated interface allow controlling disc decoding, here a broken glass-base lacquer disc.

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Playback examples

The following records were successfully digitised using our process:

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Broken glass-base lacquer disc W01770/PHD85003884, interview in Sweden of Olgor/Olmer? Ahlenius by Maurice Fleurent : "La poésie en Suède : l'influence française", broadcast on 7/09/1946. [excerpt .mp4]

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Disc 13, side 25, DC13782 "Cabaret Dolto", recorded 14/11/1951 (lacquer disc, with a few cracks). [excerpt .mp4]

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Box 73, disc 1, side A, Dargent corpus (set of 712 Spanish language broadcasts on Radio-Paris, by Spanish republican refugees, from 1946 to 1949) [full .mp4]

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Set W1425, "Voici ma carte Monsieur : L'existentialisme Pictural !", 10 minutes live recording by Pierre Sabbagh of the first French post-war (spade) duel, 1946. Zinc-base lacquer disc, severely degraded, very brittle lacquer, peeling off. [shortened to 6:30 .mp4][shortened to 2:32 .mp4]

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First recording by fado singer Maria Teresa de Noronha: Fado de Mouraria (1939). Aluminum-based lacquer disc, numerous fine cracks. [full .mp4]

Bibliography

[1] George Brock-Nannestad, "The Attraction of Optical Replay of Mechanical Recordings" (AES Conference, Oct. 2001)

[2] Louis Laborelli, Jean-Hugues Chenot, Alain Perrier, "Non contact Phonographic disks digitisation using structured colour illumination", proceedings of AES 122nd Convention - Vienna 5-8/5/2007

[3] Louis Laborelli, Jean-Hugues Chenot, Dust Detection by Colour Analysis in an Optical of Phonographic Disks Digitisation. Proceedings of ICIP 2007 (IEEE International Conference on Image Processing, San Antonio, 16-19/9/2007)

[4] French patent Louis Laborelli FR2874280, published 17/2/2006 : Équipement pour la lecture optique des disques phonographiques analogiques

[5] US, EU patent Louis Laborelli (US200604498, US7660208B2, EP1626402, DE602005002890T2) : Equipment for the optical playback of analog phonographic records.

[6] Ottar Johnsen, Frédéric Bapst, Lionel Seydoux, "Sound extraction of delackered records" proceedings of the AES conference 2008, San Francisco

[7] Vitaliy Fadeyev, Carl Haber, "Reconstruction of Mechanically Recorded Sound by Image Processing", Journal of the Audio Engineering Society (JAES), vol. 51, no. 12, pp.1172-1185 Dec. 2003

Outcomes

Roughly 20,000 of INA's 276,000 discs can no longer be played with conventional means. We are working on finalizing a version of the system that can decipher such discs. We then plan to find partners to offer industrialised systems to radio broadcaster's archives departments all over the world, or to digitizing service providers.

Team

Current team :

  • Jean-Hugues Chenot, project leader
  • Louis Laborelli, researcher
  • Jean-Etienne Noiré, R&D engineer

For their participation, we thank :

  • Alain Perrier
  • Paul Tomi
  • Patrice Maylin
  • Gilles Daigneault

Training engineers : Delphine Chadefaux, Maxime Bocquier, Aurélie Fosso, Rémi Peltier, Nicolas Grosset-Grange

We thank all colleagues from the archive department in INA for their support.

Funding / Partners

This work was supported by European Commission in the framework of PrestoSpace project (FP6-IST-507336 2004-2008), and by French Fonds national pour la Société Numérique (FSN), Cristal project (FSN-AAP1-012085-405850, 2011-2012).

Companies Indeep and Optis have contributed to the project.