Re: Sound head of the 'Moviola'

[ita katz <itakatz@xxxxxxxxx>]

Citing wikipedia was just a matter of convenience - i read
explanations of the same spirit in other sources, anyway none of them
was of an academic source.

My fault for taking 'amplitude' to be 'amplitude envelope', as you
mentioned. I figured it out a few posts ago, but didn't have achance
to respond.

On Thursday, December 30, 2010, Steve Beet <steve.beet@xxxxxxxx> wrote:
>
> 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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