Digital signal and image processing
POV
POV: you are a voice entering an ADC
POV: you are a voice wave entering an analogue-to-digital converter
Quick check · tap an answer to continue
Lesson notes
Key points
- First the anti-aliasing low-pass filter trims away your frequencies above half the sampling rate.
- Next you are sampled, frozen into snapshots at regular instants by a sample-and-hold circuit.
- Then each snapshot is rounded to the nearest quantisation level, losing a tiny bit of truth.
- Finally you are encoded as binary codewords, and you leave as a stream of ones and zeros.
Definitions
- Quantisation error
- The difference between the true sample value and the discrete level it is rounded to.
Takeaway: ADC order: filter, sample, quantise, encode.
Quick check: Which ADC stage happens before sampling to prevent aliasing?
- Binary encoding
- Low-pass filtering
- Quantisation
A low-pass anti-aliasing filter removes frequencies above fs/2 before sampling.
Anti-aliasing filterSamplingQuantisationEncoding
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