Nuts & Volts - May 2004

Tech Forum

#2 To mangle a metaphor, you're trying to pull the horse with the cart. The Society of Motion Picture and Television Engineers (SMPTE) has written the prevailing standard for dealing with synchronization in this field. SMPTE time code allows for various frame rates, specifically 30, 29.97, 25, and 24 frames per second (fps), with some rates requiring "drop frames" every so often for accurate synch. Among other things, the different rates in the SMPTE standard allow black & white and color NTSC & PAL video and motion picture frame rates to be synchronized with audio.

The "gotcha" is that this is not implemented in the industry by altering the camera or frame rate speeds; what is changed is the sampling rate of the audio. Where normally one would use strict sampling rates of 44.1 (CD), 48 (digital tape), or 96 kHz (various digital recorders) for sound, the SMPTE code causes a controlling unit to slightly alter these audio sampling rates in order to keep the media in synch. MIDI time code (MTC) can also be used in some cases, for example, synching a digital recorder with an analog tape machine.

I don't know much about Super 8, but I would imagine that, if you don't want to move to video tape, the best thing you can do is transfer your film images to digital form and then use a standard computer application, like Pro Tools, to synch up your audio and video.

Technologies that are no longer on the cutting edge lose their value quickly, even though they are still quite serviceable and can be picked up very inexpensively on eBay. I suspect that any homebrew approach is going to cost you more than a little research and some well placed bids. For more on SMPTE time code, try: www2.sfu.ca/sca/Manuals/ZAAPf /t/ time_code.html

Mark Emery Bolles

Alamo, CA

like to know what this actually means and, if possible, how to calculate the battery's actual output, the amount of time it will supply needed power, etc.

Also, is it possible to replace this battery with a homemade solution, based on something I read several issues back about super capacitors (1 farad and greater)?

If the battery is rated at 14. 8 V, 3.2 AHr, that means that, in theory, it can supply 4. 8 volts at 3.2 amps for 1 hour or 14. 8 x 3.2 = 47. 36 watts for 1 hour. In practice, this value is dependent on the discharge rate — you usually get much more life at low discharge rates. As an example, if you discharge the battery at 0.1 amps, in theory, you should get 14. 8 volts for