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Re: Sound head of the 'Moviola'

On 29 Dec 2010 at 9:47, ita katz wrote:

> Thanks for the links.
> Do you have a reference (or a short explanation) for the variable area
> encoding? I looked for it on the web, but still some aspects are not clear:
> the "RCA-Photophone" entry in Wikipedia states:
> "variable-area" film exposure system, in which the modulated area (width)
> > corresponded to the amplitude of the audio signal"
> >
> But the amplitude does not carry all the information needed to recreate the
> sound. Similarly, the "Sound-on-Film" entry states:
> stereo variable-area<http://en.wikipedia.org/w/index.php?title=Stereo_variable-area&action=edit&redlink=1>(SVA)
> recording, encoding a two-channel audio signal as a pair of lines
> > running parallel with the film's direction of travel through the projector.
> > The lines change area (grow broader or narrower) depending on the magnitude
> > of the signal.
> Again, what encodes the frequency/phase?

In this context "amplitude" actually means the 
instantaneous value of the waveform, so everything is 

Best regards,

Bob Masta
            D A Q A R T A
Data AcQuisition And Real-Time Analysis
Scope, Spectrum, Spectrogram, Signal Generator
    Science with your sound card!