LISTSERV mailing list manager LISTSERV 16.0

Help for ARSCLIST Archives


ARSCLIST Archives

ARSCLIST Archives


ARSCLIST@LISTSERV.LOC.GOV


View:

Message:

[

First

|

Previous

|

Next

|

Last

]

By Topic:

[

First

|

Previous

|

Next

|

Last

]

By Author:

[

First

|

Previous

|

Next

|

Last

]

Font:

Proportional Font

LISTSERV Archives

LISTSERV Archives

ARSCLIST Home

ARSCLIST Home

ARSCLIST  January 2011

ARSCLIST January 2011

Subject:

Re: ELP - Clareety

From:

Alex Hartov <[log in to unmask]>

Reply-To:

Association for Recorded Sound Discussion List <[log in to unmask]>

Date:

Tue, 11 Jan 2011 17:30:02 -0500

Content-Type:

text/plain

Parts/Attachments:

Parts/Attachments

text/plain (137 lines)

Hi Brecht

No, it was not my intention to check you translation, I'm just compulsive about keeping material I think interesting in it's original form.  Thank you for the speedy reply.

ON another note, I do think that the INA should be an inspiration to all of us.

Best

Alex

On Jan 11, 2011, at 12:09 PM, DECLERCQ Brecht wrote:

> Alex,
> 
> You're not going to control things on the slightest translation errors are you :-)?
> The original was at http://www.prestospace.org/training/images/Proto-Clareety.pdf
> I'd like to inform everybody that I was kindly contacted by Gerard Frappé from Indeep. He said that a prototype will be installed at INA not earlier then in April this year.
> Then still, some software development has to be done, so a market version may not be expected before the end of 2011. They just don't want to come up with an immature version.
> 
> Kind regards, 
> 
> Brecht Declercq
> Media Manager DiVA-project
> VRT - Room 2F3
> 1043 Brussels
> Belgium
> 
> 
> 
> 
> 
> -----Oorspronkelijk bericht-----
> Van: Association for Recorded Sound Discussion List [mailto:[log in to unmask]] Namens Alex Hartov
> Verzonden: dinsdag 11 januari 2011 18:00
> Aan: [log in to unmask]
> Onderwerp: Re: [ARSCLIST] ELP - Clareety
> 
> Greetings
> 
> Can you post the URL or some reference to the original?
> 
> Thank You
> 
> Alex Hartov
> 
> On Jan 10, 2011, at 6:16 PM, DECLERCQ Brecht wrote:
> 
>> Dear colleagues,
>> 
>> You'll find my translation of the French article about Clareety beneath (and completely for free!).
>> I hope there are not too many errors as French nor English is my mother tongue. And in fact I'm neither a specialist of these disks.
>> I'd like to draw everybody's attention to the fact that this is an article of October 2007.
>> I don't know what the status of the commercialization of this device is, but I hope that the fact that it was again presented in Paris at AES a month ago means it will soon be available.
>> 
>> Greetings,
>> 
>> Brecht Declercq
>> Media Manager DiVA-project
>> VRT - Room 2F3
>> 1043 Brussels
>> Belgium
>> 
>> 
>> 
>> 
>> The digital image serving the digitization of old disks
>> Jean-José Wanegh (1st October 2007)
>> Translation by Brecht Declercq
>> 
>> As a photography and phonography passionate, Charles Cros wanted to go beyond time. It's curious to see that today, sound meeting image gives us the possibility to make his dream come true. In this way, millions of phonographic records, threatened by years of time and victims of the fact that each play-out wipes out a little more the memory of these supports, are going to find a new youth, thanks to optical procedures without contact. One of these, Clareety, developed by a research team of INA, has numerous characteristics responding to the needs of archivists and restoration-specialists.
>> 
>> Although the audio quality of CD's is considered very good by the majority of listeners, there is a population of audiophiles who consider the encoding at 44.1 kHz of CD's not sufficient for a trustful reproduction of the musical treasures recorded with analog means. As an answer to this expectation, there is a tremendous offer of turntables for microgroove records. But even with the high level performance of these devices and the caring of these audiophiles for their vinyl records, every play-out still means a kind of wear-out. And although the pressure force of the read head is adapted to a minimum, there still is a mechanic contact of the needle with the sides of the groove. With every passing by, this slow scratching leads to an irreparable deterioration of the disk.
>> 
>> That's why as early as 1982, a student of Stanford University, Robert Stoddard, proved the possibility to use a laser, connected to a special arm, to realize an optical read-out without contact with the vinyl. In 1983, he created a firm called Finial Technology and with the help of Robert Stark he developed the first vinyl turntable reading out with laser. In 1989 Finial sold its patents to ELP from Japan. Only in 1991 the first ELP turntable was commercialized, while already for two years the CD sales had doubled LP's.
>> 
>> An audio heritage in danger
>> 
>> But the universe of the disks should not only be considered from an audiophiles' view, neither by the view of a nostalgic in search of lost time, when it was Teppaz to entertain our juvenile parties. As the years passed by, millions of recordings have been made around the world. For many years, phonographic recording was the only way to consign a musical, artistic, historic of political event to a physical support. Thus, an considerable amount of recordings is part of our heritage. Let's not forget that although it was invented in 1935, the magnetophone tape only appeared at radio stations after the Second World War. 
>> 
>> From the thirties until half the fifties, radio stations used directly carved disks, called disques souples, commonly known in France as Pyral. We should preserve all these recordings, but we should also make it possible to listen to them in the best possible conditions, without compromising the integrity of the supports. The problem is that we're talking about original recordings with often only one known copy. The weight of time made them fragile to the point that even one reading-out, even with a performant phono-pick-up, would destroy it forever. This motivated strongly throughout the whole world the development of no-contact read-out systems, with a diversity of optical solutions, from simply capturing the image of the disk with a scanner, to 3D-capturing of the topography of the groove using the principles of confocal laser microscopy. But sound archives' leaders don't choose an appropriate solution following the same rules as those followed by an audiophile. The reason is that at INA, the collection to be safeguarded counts 276.000 grooved disks (fig. 3). Even if optical read-out is the only way to extract the precious content of these disks without compromising their eternal life, still this chosen technique should make it possible to work without delay, with an optimal quality, using tools that can be industrialized and thus at an affordable cost of purchase and exploitation. If one knows that some technologies ask up to ten times the real time playing duration of the support for capturing them in 3D, no doubt this may be called a handicap that a lot of institutions would not be able to overcome. All these arguments were thus considered, when a team of INA researchers completed an original system for the optical analysis of the groove of a disk by colorimetric encoding of the variations of the gradient, in relation to the axis of the track.
>> 
>> ELP, the first laser turntable serving wealthy audiophiles
>> 
>> In this article, unfortunately it is not possible to make an overview of the range of all the solutions making use of optical read-out, going from those that are planned for the future, from whom some already have been commercialized, or at the point of industrialization, to those still in the prototype stadium. All these systems can be classified in multiple ways.
>> 
>> Firstly, there are systems working in real time, with the optical information directly being converted in an analog audio signal. In this system there is no signal processing. The ELP turntable is of course a typical example here.  The light produced by a laser is divided in five rays. Two of them are meant to follow the track of the disk by detecting the 'shoulders' of the groove (the tops of the sides). After the reflection, these rays are digitized and then treated to serve tracking. Two other rays lighten the flanks of the groove on an adjustable height, to benefit from a zone where the needle did not leave traces of wearing the groove out (fig. 6). 
>> 
>> The reflected and modulated light of the sides of the groove is sent back to a detector that converts the light signal into an analog audio signal. The fifth ray allows to control the altitude of the optical pick-up arm, in function of deformations of the disks and to adapt to different widths. If the barrier of the cost of these turntables is overcome, this solution may have several advantages to convince audiophiles and one would be tempted to believe that already with this device we have the ideal tool for the transfer of all phonographic collections of the whole world. But nothing is less true in fact. It is an excellent tool for reading out vinyl and 78 rpm LP's in excellent condition. The majority of tests by audiophiles speak with praise about this technique, but the systems has huge problems to cope with scratches and dust. The system is unable to read from transparent or colored vinyl, or materials transparent to the wavelength of the laser. We see the same impossibility with directly carved acetate disks. It is impossible to read the 78 rpm's with a vertical groove, as the rays have been conceived to detect the lateral modulation. It's also important that the form of the needle is V-shaped. Round-carved sides of the groove could create distortions. To assure a correct following of the track, it is necessary that the top of the needle and the surface of the disk come together in a perfectly defined angle. In case of a border rounded off, the tracking will be impossible. The last issue is that scratches or bits of dust could deviate the system from the groove, in some cases ŕ cheval (spread) over two adjacent tracks, one ray reading the side of one groove, the other reading the opposite one of its neighbor.
>> 
>> In the nineties Juraj Poliak, an associated researcher of the Ecole Polytechnique Fédérale de Lausanne (CH), developed a real time read-out system using an optical fiber, with a glass ball on its edge, to follow the groove of a disk or a cylinder. This fiber allows to take a laser ray into the groove, that after the reflection towards a photo-detector takes into account the lateral and vertical shifting of the original cell. This system is very simple in its concept and it has the advantage of being able to read the lateral grooves as well as the vertical ones. Poliak is now retired, and his method seems never to have gone beyond the prototype stadium. 
>> 
>> Read-out without contact by digital imaging
>> 
>> After these real time systems came the systems that in a first stage produce an image of the disk or the groove, measuring then its width, to finally extract the digitally processed audio information. On this terrain, two projects are taking place. One of them, named IRENE, is lead by a team of two researchers, Vitaliy Fadeyev and Carl Haber of the Lawrence Berkeley National Laboratory. The other project one was born at the Lausanne School of Engineering, and lead by Ottar Johnsen, with active participation of Sylvain Stotzer, who made his PhD in information science on this subject. The team of Berkeley works in the field going from  applied optical metrology to particle physics, the latter being the source of the idea to make a trace of micro-images of the surface of the disk, that after processing will allow to reconstruct the complete image of the groove. Typically these are 700 µm to 540 µm pictures, containing multiple parts of grooves (fig. 7). In case of a 78 rpm disk of 25 cm, this means 100.000 snapshots have to be made for a data-volume of 1 Gb to 1 Tb. On this level it is possible to process the image, to eliminate certain defaults caused by particles, scratches or the disk being worn-out. After photographing, it's all about measuring in every point the position of the border of the groove, compared to the middle of it.  With this technique, only the disks with a lateral groove can be treated. Disks with a vertical groove, like cylinders, are analyzed with a confocal microscopy-device using laser, which is a very heavy technique to setup. Ottar Johnsen and Sylvain Stotzer's approach is very different. They make one high resolution picture of the disk, which is digitized afterwards via polar coordinates, with a scanner specially developed for this purpose named VisualAudio. Here too a precise identification of the borders of the groove has to be done to measure their position. 
>> 
>> Whether it's about this Swiss project or the one of Berkeley, in the two cases the subject of the captured information is the position of the sides of the groove. But, as many of you know, the amplitude of the audio signal is not proportional to the position of the needle, but to the speed of its lateral shifting (fig. 8). And thus, to know this speed, we have to calculate the derivation of the curve that determines the position of the groove. This makes it necessary to have an excellent resolution to measure the position of the groove at its beginning, typically 1 micron per pixel.
>> 
>> In France, INA prefers to see a mirror in every disk
>> 
>> In France a research team of INA directed by Jean-Hugues Chenot has chosen an original direction, starting form a relatively simple but long known constatation, to develop its optical digitization unit for old disks. The idea is to keep in mind that every side of a groove behaves as a mirror.
>> 
>> It's important always to remember that using a lateral modulation, the radial speed of the grooving needle is proportional to the amplitude of the signal. So every angle formed by the side of the groove and the tangent of the circle that describes the rotation of the disk is a result from the combination of the radial speed of the graver and the tangential speed of the disk (fig. 10 and 11). If now we lighten the flank of this groove with a bundle of light with certain characteristics, and we analyze then the reflected light, we should be able to discover the sound information that is recorded on the disk.
>> 
>> There is a precedent of this method, known by all sound engineers who have engraved disks as the Buchmann-Meyer method. This method was used to verify the engraving-characteristics of their device. Rather than measuring with a microscope the amplitude of the groove, one measures the width of the luminous strip, reflected by the side of the groove when the disk is lit from a distance with a parallel bundle of light. In every point the width of this strip is proportional to the speed of the engraving, and thus to the amplitude of the sound. This measuring technique was already used for the engraving of 78 rpm's. These engraving test disks were called waxographs.
>> 
>> But the difference with the method developed by the research team of INA is that this method is used only as a way to control things. It doesn't allow to optically read-out the content of the disk.
>> 
>> Reading out the sound by a colored, structured illumination
>> 
>> The great originality of the method proposed by Jean-Hugues Chenot is to encode the incident light in various colors. So, at the inside of the continuous colored spectrum coming from a filter at the end of an optical condenser, every colored ray is characterized by his incident angle. While this rainbow-colored bundle, of whom all rays that converge into one point, hits the side of the groove, every elementary colored ray is reflected in an angle that is the same as its incidental angle (always conparing to the norm) in this point of the groove (cf. Descartes' law of reflection). If we put a sensor in a well-determined angle on the path of the reflected bundle, only the colored ray with the right incidence (compared to the gradient of the side of the groove) will be reflected in the direction of the sensor (fig. 12 a, b, c). Doing so, we have an encoding related to the color of the angle of the groove.
>> 
>> If instead of a simple sensor we put a color video camera, it's not a point per point analysis anymore. Within the field covered by this camera, multiple parts of the groove can be simultaneously analyzed. Typically every image covers a zone of 2mm by 2mm and includes eight tracks (in the case of a 78 rpm), of which six are taken into account with every analysis (fig. 13). We thus obtain a useful image of 400 by 400 pixels. But one of the big advantages of this method, compared to the others that have been described earlier, is that this camera carries out a high speed measurement of the whole disk. From a measurement from point to point we thus go to acquiring several millions of points per second. With a rate of 60 images per second, a whole disk can be done in a time-span close to the real time duration of the disk (18O seconds). Thanks to this method, it is not necessary anymore to have the high resolutions needed in the methods of Carl Haber or Sylvain Stotzer. In this method, we have enough with 5µm per pixel, considering that it's not the position of the groove that is being measured. To this, another considerable advantage can even be added: the height of the side of the groove is sufficiently important to cover multiple (ca. 30) pixels. As the groove thus seems to be composed by different parallel tracks, redundancy is entering the signal.
>> 
>> Error treatment by the image
>> 
>> Errors that have been established in the grooves may be due to a bit of dust, or a contamination coming from the exudation of a plasticizer, as is often the case with acetate disks. Errors like these diffuse the light, instead of reflecting it. In some cases the sides of the grooves are marked with almost parallel scratched as a result of an abrasion caused by a wrongly adjusted needle or an excessive pressure. In the case of a directly engraved disk, this phenomenon may be caused by the harmful effects of a damaged needle. In similar circumstances a calculation of the average depth of the trace in the total length of the groove may free the result from traces of abrasion. In general these errors can easily be detected. A cartography of these can even be drawn up to cancel them or to reduce their effects during the processing of the image, even before extracting the audio signal.
>> 
>> This cartography of errors will eventually help to draw a file with metadata, that during the digital processing of the signal will provide the exact position of the errors. For these errors some restoration technique will have to be applied. But bearing in mind that a correction is never completely neutral, we avoid to tackle the signal where it is healthy. On the longer term, the system should also be able to carry out an automatic detection and correction of cracks as seen on the 'marble-lined' disks, as reconstructing these puzzles is no more than a software issue (fig. 14). In the case of a 78 rpm disk, this system offers 240.000 samples per second on the outside. At the centre of the disk there are still 78.000 samples per second. This means that compared to a digital signal of 48 kHz, we still have a comfortable over-sampling. The response in matters of frequency is very good and allows to detect details of a signal down to 15 kHz on a 78 rpm. Of course, in case of a 33 kHz micro-groove, this sampling is seriously being reduced because of the slower rotation speed of the disk. This effect can easily be compensated by an appropriate magnification of the optics of the camera. But, as everybody knows, before ending up with a complete reconstruction of the audio signal, it is a collection of images of whom a certain number is deliberately operated as an overlap zone. To cover a 30 cm disk, circa 24.000 images are made. During this acquisition the camera is positioned on a radius that remains the same during the complete rotation of the disk. In this way a series of images is made forming a crown. From this crown the image processing software calculates the junction points of the six observed tracks, thanks to the overlap zones of these images. After decoding, we obtain thus the equivalent of a multi-track piece of audio, covering a duration corresponding to the time needed for one complete rotation of the disk, or 769 ms. In this way the whole disk will be decomposed into crowns of multi-track audio with a length of 769 ms.
>> 
>> Don't hesitate to follow the gradient
>> 
>> Today this system named Clareety has already been tested at INA and the results are promising. It's development is part of the PrestoSpace project. In 2006 INA associated with an industrial partner, INDEEP from Annecy (F), aiming to industrialize and commercialize it. The system responds completely to the goal it was designed for: no-contact reading-out acetate disks that were recorded from the thirties to half the fifties, especially those for which the fragile state doesn't allow any read-out using a needle (fig. 15). The test particularly proved that direct digitization from the gradient of the grove offered a bigger sensibility of the system than the sensibility coming from calculating the width of the groove followed by a calculation of its derivative function. But way beyond this first goal, this system has proven its capacity to read-out 78 rpm's with lateral engraving that have been commercialized in the fifties, just as the first Berliner disks characterized by a very particular groove profile. A deviation at 90° of the optical read head allows moreover to read Pathé-Saphir disks with a vertical engraving. Also the read-out of 33 rpm's is proven. Inevitably we come to the question of stereo disks. Two solutions are possible. The first is reading for example the outside of the groove (right channel), then the inside (left channel) and then synchronizing the two tracks to get a stereo signal. This solution doubles the time to take the images. The second solution consists out of installing a second optical head to scan simultaneously the other side of the groove. In that case the system is a little more complex and costly, but also realizable. To read bent disks (victims of a 'curtain effect') without a hitch, the system will be equipped with an automatic correction of the altitude, keeping a perfect focalization during the whole rotation of the disk. Normally, at the end of this year, a first industrial system will be available.
>> 
>> A new vision on the analog world
>> 
>> Finally we can say that the solution proposed with this INA-system is as far as we know the only system for optical analysis and digitization of disks that's being industrialized. It's major asset is the availability on the market of a product that meets the technical and economic requirements of archiving institutions, as well as those of audio restoration professionals. As far as we understood, this system would cost little more than an ELP turntable. Of course we're still far from a system that's affordable for aficionados of rare recordings. But what's important, is that from now on we can be sure to find a system capable of extracting thousands of hours of recordings out of these phonographic pieces. There's good hope that finally a lot of archiving institutions will be able reveal these fragile memories. Thus, for once, the marriage of the digital and the optical doesn't consign the old analog carriers to the attic, but helps them to assure an eternal life.
>> 
>> *** Disclaimer ***
>> 
>> Vlaamse Radio- en Televisieomroeporganisatie
>> Auguste Reyerslaan 52, 1043 Brussel
>> 
>> nv van publiek recht
>> BTW BE 0244.142.664
>> RPR Brussel
>> http://www.vrt.be/disclaimer

Top of Message | Previous Page | Permalink

Advanced Options


Options

Log In

Log In

Get Password

Get Password


Search Archives

Search Archives


Subscribe or Unsubscribe

Subscribe or Unsubscribe


Archives

February 2020
January 2020
December 2019
November 2019
October 2019
September 2019
August 2019
July 2019
June 2019
May 2019
April 2019
March 2019
February 2019
January 2019
December 2018
November 2018
October 2018
September 2018
August 2018
July 2018
June 2018
May 2018
April 2018
March 2018
February 2018
January 2018
December 2017
November 2017
October 2017
September 2017
August 2017
July 2017
June 2017
May 2017
April 2017
March 2017
February 2017
January 2017
December 2016
November 2016
October 2016
September 2016
August 2016
July 2016
June 2016
May 2016
April 2016
March 2016
February 2016
January 2016
December 2015
November 2015
October 2015
September 2015
August 2015
July 2015
June 2015
May 2015
April 2015
March 2015
February 2015
January 2015
December 2014
November 2014
October 2014
September 2014
August 2014
July 2014
June 2014
May 2014
April 2014
March 2014
February 2014
January 2014
December 2013
November 2013
October 2013
September 2013
August 2013
July 2013
June 2013
May 2013
April 2013
March 2013
February 2013
January 2013
December 2012
November 2012
October 2012
September 2012
August 2012
July 2012
June 2012
May 2012
April 2012
March 2012
February 2012
January 2012
December 2011
November 2011
October 2011
September 2011
August 2011
July 2011
June 2011
May 2011
April 2011
March 2011
February 2011
January 2011
December 2010
November 2010
October 2010
September 2010
August 2010
July 2010
June 2010
May 2010
April 2010
March 2010
February 2010
January 2010
December 2009
November 2009
October 2009
September 2009
August 2009
July 2009
June 2009
May 2009
April 2009
March 2009
February 2009
January 2009
December 2008
November 2008
October 2008
September 2008
August 2008
July 2008
June 2008
May 2008
April 2008
March 2008
February 2008
January 2008
December 2007
November 2007
October 2007
September 2007
August 2007
July 2007
June 2007
May 2007
April 2007
March 2007
February 2007
January 2007
December 2006
November 2006
October 2006
September 2006
August 2006
July 2006
June 2006
May 2006
April 2006
March 2006
February 2006
January 2006
December 2005
November 2005
October 2005
September 2005
August 2005
July 2005
June 2005
May 2005
April 2005
March 2005
February 2005
January 2005
December 2004
November 2004
October 2004
September 2004
August 2004
July 2004
June 2004
May 2004
April 2004
March 2004
February 2004
January 2004
December 2003
November 2003
October 2003
September 2003
August 2003
July 2003
June 2003
May 2003
April 2003
March 2003
February 2003
January 2003

ATOM RSS1 RSS2



LISTSERV.LOC.GOV

CataList Email List Search Powered by the LISTSERV Email List Manager