Subject: Re: Sound head of the 'Moviola' From: ita katz <itakatz@xxxxxxxx> Date: Thu, 30 Dec 2010 08:18:41 +0200 List-Archive:<http://lists.mcgill.ca/scripts/wa.exe?LIST=AUDITORY>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@xxxxxxxx On Behalf Of James Johnston > Sent: Wednesday, December 29, 2010 9:47 PM > To: AUDITORY@xxxxxxxx > 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@xxxxxxxx > On Behalf Of Kevin Austin [kevin.austin@xxxxxxxx > Sent: Wednesday, December 29, 2010 1:29 PM > To: AUDITORY@xxxxxxxx > 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. > > > > > Notice: > This message and any included attachments are intended only for the use of > the addressee, and may contain information that is privileged or > confidential. If you are not the intended recipient, you are hereby notified > that any dissemination, distribution or copying of this communication is > strictly prohibited. If you have received this communication in error, > please destroy the original message and any copies or printouts hereof. >