spectrogram — ONED signal op

• データ種: signal → image2d

• 呼び出し: import fullseye as fs; fs.ledger.spectrogram(x, rate=1.0, win=256, hop=None) (実装を直接呼ぶなら import dsp; dsp.spectrogram(x, rate=1.0, win=256, hop=None)、台帳から引くなら ops1d.get("spectrogram"))

• 台帳経由の戻り値: fullseye.ledger.spectrogram(...) は**宣言 out 型 image2d の値だけ**を返す(本体は補助情報も返す)。捨てられた側が要るときは fullseye.ledger.spectrogram.raw(...)、または dsp.spectrogram を直接呼ぶ。

• 本体の返り: (freqs, times, S) — S が本体

使い方

STFT magnitude spectrogram -> `(freqs, times, S) with S` shape

`(n_freqs, n_frames). Hann-windowed; *hop* defaults to win//2`.

**Same raw convention as :func:spectrum, but a different divisor.** Each

column is the unnormalised `|rfft(frame * hann(win))|`, so it is not an

amplitude either — and dividing by `2/win` is *wrong* here, because the

Hann window has already thrown away part of the signal. The correct one-sided

amplitude conversion divides by the window's coherent gain::

w = np.hanning(win)

amp = S * (2.0 / w.sum()) # bins 1 .. win/2-1; DC / Nyquist: 1/w.sum()

Measured on a unit sine at a bin centre (`rate = 16000` Hz, 1000 Hz,

amplitude exactly 1.0, `win = 256`): the raw column peak is

`63.7497786196906; * 2/win gives 0.49804514546633283` (too small by

exactly the Hann coherent gain `sum(w)/win = 0.498046875`), while

`* 2/sum(w) gives 0.9999965273676957`. Only the second one is the

amplitude that was actually in the signal.

Peak *positions*, frame-to-frame ratios and any dB *difference* are unaffected

by either factor. This function returns magnitudes only — the phase is

discarded, so it cannot be inverted; use `acoustics.stft / acoustics.istft`

for a round-trip.

参考(サンプルデータ・文献)

• サンプルデータ カタログ(DL URL / ライセンス) — 2-D は skimage.data(BSD/public)+ 合成、3-D は実データ源(Stanford/PDS 等)の DL URL。

• 演算子の来歴・参考文献 — この op 族の元になった研究/手法の出典。

• アルゴリズムの正典(著者・年)と用途は上記ファミリ使い方ガイドに記載。

実行できる例(この op を実際に呼ぶ検証済みサンプル)

• acoustic_condition_monitoring — py -3.11 examples/acoustic_condition_monitoring.py

型が繋がる次の op(image2d を入力に取れる)

—

同カテゴリ(signal)

lowpass · highpass · bandpass · envelope · rms · local_std · quantize · companding_mu_law

*Provenance: dsp.py — ONED operator registry. この per-op ノートは tools/opdocs.py md が自動生成(手編集しない)。*

© 2026 Kazufumi Furuse — Fullseye operator documentation. Licensed under Apache-2.0.