Subject: Re: Sound head of the 'Moviola' From: Bob Masta <audio@xxxxxxxx> Date: Wed, 29 Dec 2010 08:23:35 -0500 List-Archive:<http://lists.mcgill.ca/scripts/wa.exe?LIST=AUDITORY>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 included. Best regards, Bob Masta D A Q A R T A Data AcQuisition And Real-Time Analysis www.daqarta.com Scope, Spectrum, Spectrogram, Signal Generator Science with your sound card!