Re: Sound head of the 'Moviola'

[Steve Beet <steve.beet@xxxxxxxx>]

Sorry to point out the glaringly obvious, but this thread seems to be
getting rather surreal.

The confusion seems to have started because Wikipedia has been used as a
reference point, and the respective article has used inappropriate
nomenclature. The word "amplitude" was used in the original article not in
the currently accepted sense, but to mean what might be phrased as "signal
value, with a DC offset sufficient to ensure that that value is always
positive". In other words the area of the clear part of the film represents
the waveform itself (with a DC offset). There is no processing involved - no
Fourier or Hilbert analysis - just a raw signal. Forget phase, frequency,
etc. - just feed the output of a photodiode/phototransistor detector into an
amplifier and you should get the audio you're after!

I would strongly recommend never using Wikipedia alone as a source of
information. Most of the articles are not written by true experts and they
are not scientifically rigorous or exact.


Steve Beet



-----Original Message-----
From: AUDITORY - Research in Auditory Perception
[mailto:AUDITORY@xxxxxxxxxxxxxxx] On Behalf Of James Johnston
Sent: Wednesday, December 29, 2010 9:47 PM
To: AUDITORY@xxxxxxxxxxxxxxx
Subject: Re: Sound head of the 'Moviola'

There is no need for "quantization".
 
Frequency and phase are the Fourier Transform (which is a linear,
energy-preserving transform) of Amplitude in the time domain.
 
The Fourier Transform is really a complex, but it often gets converted to
polar. More convenient sometimes, less so sometimes.
 
________________________________

From: AUDITORY - Research in Auditory Perception [AUDITORY@xxxxxxxxxxxxxxx]
On Behalf Of Kevin Austin [kevin.austin@xxxxxxxxxxxx]
Sent: Wednesday, December 29, 2010 1:29 PM
To: AUDITORY@xxxxxxxxxxxxxxx
Subject: Re: [AUDITORY] Sound head of the 'Moviola'



In the time domain, as Hugh Le Caine used to say, everything is amplitude
(displacement). As I understand this, frequency and phase are derived from
amplitude in [quantized] time.

Kevin




On 2010, Dec 29, at 2:47 AM, ita katz wrote:


	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?
	
	Thank you
	
	Ita.




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