FA-91548 / Digital signal filters / Member archive

Polyphase decimator drops the last partial output · case 03

For a length not divisible by D the final output sample is missing.

Member previewVariant 3 · 3 implementations · 7 checks per implementation

Case contract

Input [h, D, samples] (integers). Output y[m] = sum_k h[k] x[mD - k] for m = 0 .. ceil(len/D) - 1 with x = 0 outside the signal, computed through the polyphase split E_p[j] = h[jD + p].

Why this case matters

Polyphase decimators avoid computing discarded outputs; commutator and phase-split slips alias the output.

One recorded failure

Sample boundary fixture

This sample comes from the broken implementation of a controlled reproducer.

Boundary fixture	Actual	Expected	Outcome
regression: random polyphase 4	`[0, -6, 16]`	`[0, -6, 16, 6]`	Failed

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