buchwandler

TD-PSOLA listening evaluation — 2026-07-31

Status

This is the milestone-5 evaluation record and reproducible protocol for the experimental direct TD-PSOLA speech path. No default method is changed by this work. Listener results remain pending until a licensed corpus and at least two development listeners are available; this file deliberately does not invent ratings.

The implementation now uses approximately-two-period centered grains, local-F0 pitch-mark propagation, tracker voiced intervals for synthesis masking, and an explicit insufficient-mark fallback. Synthetic leakage, normalization, sample- rate, noise, and reverberation checks are automated; they do not constitute the real-speech listening gate below.

Corpus and reproducibility

Use licensed or consented 16/24/48 kHz mono or stereo WAV material and record, for every source: corpus/license, attribution, sample rate, filename or stable identifier, channel count, and whether the segment is clean, noisy, breathy, creaky, reverberant, or TTS-generated. Do not commit private speech recordings.

Render with:

python scripts/compare_speech_effects.py INPUT.wav OUTPUT_DIR \
  --rates 0.8 1.0 1.25 --semitones -6 -4 -2 2 4 6

The comparison output records exact-length error, finite output, RMS/peak, continuity jumps, runtime, and generated WAVs. Keep metrics.json and the command line with the evaluation notes.

Listening matrix

Include lower- and higher-pitched voices, breathy voice, rapid F0 motion, plosive-rich and fricative-rich text, mixed voiced/unvoiced speech, a short TTS fragment, silence boundaries, mild noise, creaky/fry speech, and intelligible reverberant speech.

Compare the unmodified reference, current WSOLA plus resampling, current ESOLA plus resampling where its rate is supported, phase-vocoder diagnostics, and direct TD-PSOLA. Randomize A/B or ABX order and do not reveal method names.

For each trial, collect 1–5 ratings for naturalness, intelligibility, speaker or timbre preservation, pitch correctness, buzziness, flutter, echo/reverb, transient duplication, unvoiced tonalization, clicks, and overall preference. Record severe-artifact flags and free-text comments.

Promotion gates

  • At least two listeners for development screening and at least ten before any default-method consideration.

  • TD-PSOLA preferred over current WSOLA pitch shifting in at least 65% of moderate ±2/±4 semitone trials.

  • Severe artifacts below 5% of trials, with no intelligibility regression.

  • Objective synthetic and runtime gates pass alongside the listening result.

Until these fields are populated and reviewed, TD-PSOLA remains experimental and the existing defaults remain phase vocoder for generic time_stretch and WSOLA for apply_speech_effects.