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Getting animated about sampling | Cypress Semiconductor

Getting animated about sampling

I just got back from a screening of the 1963 film 'Jason and the Argonauts', introduced by Ray Harryhausen himself.  90 this week, Harryhausen was a leading exponent of stop-frame animation, and influential on countless filmmakers since.

When combining stop-frame animation with live performance, the live footage is back-projected a frame at a time behind the animated models.  Their small incremental movements are rephotographed together with the 'live' backdrop.  When the resulting shots are played back, you get the illusion of animated models 'acting' in perfect sync with the live cast of the movie.

As I was watching this, it occurred to me that there are significant parallels between this sort of approach and the common use of sampled data techniques in signal processing these days.  The 'live' footage is obtained by sampling the analogue dynamics of the actors at typically 24 frames per second.  When it's replayed in the cinema, our persistence of vision acts as a lowpass reconstruction filter.  We don't see the jerkiness of the sudden shot-to-shot changes, just an impression of the original dynamics (falsified occasionally by aliasing, but that's another story...).

We can do the same sort of thing in a mixed-signal processing engine like PSoC3.  The example that came to my mind was creating a little digital synthesiser to 'play along' with an incoming audio signal.  Imagine singing into a microphone which is driving PSoC3's main ADC, set to sample your analogue warblings (Bernard Herrmann's great score for the film, perhaps?) at say 48kHz/16bit.  We can make a little programmable digital oscillator running on the Digital Filter Block, combined with some envelope shaping and a little 70's synth-rock filter.  For the 20.8us that each input sample is sitting there - the equivalent of the film frame - the program running on PSoC3 is acting as a little stop-motion animator, making numerous small changes to parameters of another new sound.

Then we mix them together and send them back out - perhaps up the USB interface to your PC where you're re-recording this.  The result - a live actor (you) and a stop-motion skeleton with a sharp sword and a bad attitude (well, here's hoping the synth sounds that good), acting together in perfect sync!

Think about what other cool things you can do with PSoC3 that are  analogous (or should that be digitalogous?) to Ray Harryhausen's masterful animation.  Happy sampling! - Kendall

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