this post was submitted on 16 Jul 2023
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Showerthoughts
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I should have been more clear: The negative effects of quantisation. Obviously sampling into discrete values is shown but not the negative consequences that can have.
A DAC interpreting the blue trace will output something extremely close to the red one. There might be a slight bit of error in it due to the quantisation before but the graph does not show that and it probably couldn't since it'd be so tiny. A good way to show quantisation noise would be a histogram with a signal in the middle and some quantisation noise around it.
The DAC would not output the jaggy line. It couldn't, that's not a valid analog signal. Painting the steps between the points can be done if your audience knows what that means but can be extremely misleading if it doesn't. Those lines between the points with 90 degree angles don't exist in the real world, they're just interpolated between the points in the visualisation.
A much better way to represent digital samples in such a chart is the way it's done in the wikipedia article on the topic: https://en.wikipedia.org/wiki/Sampling_(signal_processing). They're just discrete points. If you did the same interpolation between the points as a DAC would do (which is not nearest-neighbour interpolation), you'd get the analog trace shown.