|
|
 
|
|
Author
|
Topic: Reading analogue tracks digitally.
|
Stephen Furley
Film God
Posts: 3059
From: Coulsdon, Croydon, England
Registered: May 2002
|
posted 05-30-2004 03:51 AM
It seems to me that it would be possible to read an analogue sound track in a similar way to a digital one; i.e. to scan across the width of the track, reading a number of pixels, and then represent these as a digital bitstream. Since any given point on the track will be either black (or cyan) or clear, only one bit would be needed to represent each pixel. For example, a Dolby stereo track might produce a pattern of bits something like this:
0000011111111110000000000000111100000000
with a '0' representing black, and a '1' representing clear. Counting the number of '1' bits would indicate the width of the track at that point, so in this example the Lt channel has a width of ten units, while the Rt one has a width of four units. In practice you would use more pixels than this, but the idea is there.
Any type of VA track could be read by this means, a unilateral track might produce something like:
0000011111111000000000000000000000000000
It seems to me that there would be certain advantages in reading a track in this way:
The threshold level at which a pixel is interpreted as a '1', rather than a '0', could be adjusted so that, for example, a track printed with a very low density, or one with an unusually high density in the clear areas could still be read as 'black' and 'clear', and the light passing through the low density 'black' areas would effictively be ignored. Rather similar to copying the track on a very high contrast stock. This should give a reduction in noise compared to a conventional sound head.
Some error correction would be possible. For example, if the stereo sample above were read as
0000011111100110000000000000111100000100
this is clearly not correct, the two '0's in the Lt track are probably the result of dirt on the print, while the '1' near the right hand end could be an emulsion scratch, or negative dirt. Both of these could be corrected, though this would not always be the case. if the sample were read as
0000000011111110000000000000111100000000
where the error is at the edge of the clear area, then this could be detected, but not corrected. The centre line of the Lt track has shifted to the right, but this could be due to either false '0's on the left, as in this case, or false '1's on the right. There would be no way to tell which.
The system could be configured to ignore certain pixels. For example, when reading a duo-bilateral or stereo track you would want to ignore a few pixels in the centre, between the two tracks, but when reading a unilateral track you would want to include these. It would also be possible to turrn on or off certain pixels to correctly read a track mis-aligned on the print, or a scratch on the track.
I can think of two possible disadvantages to this system:
It would require totally different hardware to a normal analogue sound head.
While it could be configured to read any type of VA track, it could not read a VD one.
Has anyone actually built a sound head which works in this way, possibly for reading old tracks for restoration, or video transfer?
| IP: Logged
|
|
John Anastasio
Master Film Handler
Posts: 325
From: Trenton, NJ, USA
Registered: Sep 2000
|
posted 05-30-2004 06:45 AM
The particular system you've described would actually increase the amount of distortion in a system. The bitstream you've proposed as an example may be binary in the sense that it uses only ones and zeroes, but it's not based on base two arithmetic. In other words, it's not a real digital conversion because it's not using the binary code. In addition, you'd be chopping the signal into disrete samples, and that introduces its own problems. A variable area soundtrack is already binary in one sense...it's either white or it's black at some spot along the width of the track, but the area is infinitely variable. What you're proposing is, in effect, some sort of A/D converter that looks at the width of the track at any given point in time and converts it to a true digital bitstream. That can already be done by simply taking the analog output of the cell and running it through such a device. Using a more expensive and complicated reader to simply look at the width of the track doesn't gain you anything. Your system simply changes the "area" coefficient into a string of ones, which then would have to be decoded and translated into a proper binary code. This would also introduce a delay. You don't gain anything by doing it that way. It would be cheaper to buy a reverse scan reader.
| IP: Logged
|
|
|
|
|
|
Steve Kraus
Film God
Posts: 4094
From: Chicago, IL, USA
Registered: May 2000
|
posted 05-30-2004 03:02 PM
Since everything DIGITAL is better, why not Digital AIR as well?
Technicolor Debuts Precision Technology for Restoring Optical Film Soundtracks to European Community
New technology has demonstrated ability to optimally restore and preserve optical audio for future generations
BURBANK, California and PARIS, October 31, 2002 - Technicolor Creative Services, a Thomson service and the post-production arm of Technicolor Entertainment Services (TES), a leading provider of end-to-end post-production and distribution services to content providers in the broadcast, cable, feature-film and ancillary home entertainment markets, announced today the European debut of Digital AIR™ - a new high-definition method to optimally restore optical soundtracks.
Technicolor Digital AIR is now available via Technicolor Creative Services' London facility, following a successful introduction in North America earlier this year. The new patented Audio Image Restoration hardware/software solution will further extend the restoration and post-production capabilities offered to European clients - enabling successful and optimal restoration of audio tracks once regarded as beyond repair.
Digital AIR works by employing precision high-definition optics to capture high-resolution images from optical audio tracks and transfer them onto multi-processor computers. Once the images are stored onto disc, Technicolor Creative Services' patented image processing software is used to clean and restore the resulting high-definition digital images.
Many of the optical tracks for which Digital AIR was designed came about during what is commonly regarded as the Golden Age of Film - the period from about 1930 to 1950 - and are among the most susceptible to generational loss due to the effects of time. Once deemed beyond repair, there was virtually nothing that could save them -- until the advent of Digital AIR.
Following its initial U.S. installation in early 2002, Digital AIR was employed to successfully restore the audio tracks in several dozen short films from the "Three Stooges" -- in preparation for a sizable DVD collection released by Columbia Tristar Home Entertainment.
"Digital AIR represents a significant step forward for film audio-restoration technology," said Bob Beitcher, president, Technicolor Creative Services. "This technology has already proven itself in the U.S. and is poised to optimize Europe's rich film legacy with the same cutting-edge audio restoration tools and techniques."
Restoring optical audio tracks has traditionally been done using noise processors and filtering/editing systems. As powerful as these systems are, at best they are time-consuming and expensive. Even worse, digital signal processing can result in undesirable artifacts like loss of high frequency, sibilant hype, and phase anomalies.
"There is absolutely none of this with Digital AIR," asserts Jaime Valenzuela, Technicolor Creative Services R&D engineer and principal designer of the solution. "The system operates at extremely high resolution and entirely in a graphical domain. There are no phase anomalies, filtering, or EQ effects at all because there is no audio processing. The technology gives Technicolor Creative Services' engineers a powerful and time-saving tool that does not rely on conventional photographic techniques or audio processing."
Valenzuela spent two years researching and building the software code that powers Digital AIR. For Valenzuela, the project was truly an example of necessity being the mother of invention. "We used to battle these optical tracks for hours to get a decent sounding track, and even then, there was always a point at which audio processing, no matter how effective, starts to produce artifacts of its own. There were other anomalies like perf-buzz that are practically impossible to remove with software. I just kept thinking that if I could capture those images digitally, I could do anything I wanted graphically and be able to produce a truly optimized track."
Part of the Digital AIR tool-kit includes advanced "modeling" software that digitally emulates the optical printing process. This capability was vitally important to producing better sounding tracks by virtue of being able to control the image digitally far beyond the parameters available in the traditional photo processing -- without the expense of printing. The ultimate goal was to produce a better sounding track than anything achieved from a print, while eliminating associated printing costs.
"We are committed to utilizing the latest technology to deliver the highest-quality end-product to our clients," states Beitcher. "We are pleased to offer Digital AIR to the European community as an extension of this mission."
With a full spectrum of market-leading audio, post-production and distribution services, Technicolor Creative Services is well-positioned to provide a complete end-to-end solution for content holders in the European marketplace.
| IP: Logged
|
|
|
|
|
|
|
|
|
|
All times are Central (GMT -6:00)
|
|
Powered by Infopop Corporation
UBB.classicTM
6.3.1.2
The Film-Tech Forums are designed for various members related to the cinema industry to express their opinions, viewpoints and testimonials on various products, services and events based upon speculation, personal knowledge and factual information through use, therefore all views represented here allow no liability upon the publishers of this web site and the owners of said views assume no liability for any ill will resulting from these postings. The posts made here are for educational as well as entertainment purposes and as such anyone viewing this portion of the website must accept these views as statements of the author of that opinion
and agrees to release the authors from any and all liability.
|
Home
Printer-friendly view of this topic