fullseye

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)

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同カテゴリ(signal)

lowpass · highpass · bandpass · envelope · rms · resample · spectrum · zero_crossing_rate

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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.

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