Digital signal and image processing
DM thread
Why do car wheels spin backwards on video?
Why do wheels look like they spin backwards in videos?
Quick check · tap an answer to continue
Lesson notes
Takeaway: Sample too slowly and high frequencies disguise themselves as low ones.
Quick check: What do you call a high frequency that appears as a false lower one after undersampling?
- A harmonic
- An alias
- A quantisation step
Undersampling folds high frequencies down into false low ones called aliases.
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