IMO he pulls a sleight of hand when using the word 'DAC'. As an DAC system it closely reproduces the original waveform but the data stream will generate a stair-step output (zero hold 'DAC' to analog filter to approximate the Sinc function) if we just dumbly decode it to a analog signal without more processing. The fact that the processing is now internally digital so we never see it as a analog signal is a little misleading (I'm sure he knows that) because it's still there mathematically as encoded signal spectra that must be handled by a filter of some kind like Sinc Interpolation/convolution that all have the same mathematical function as a band-pass analog filter.Well fine, but the exact waveform gets reproduced from a sampling of that waveform. Some how the DAC comes up with a best-fit (or is it an exact analytical) solution?

http://demonstrations.wolfram.com/SincInterpolationForSignalReconstruction/

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