normalize_text() handles three Whisper quirks that produced messy F5
ref_texts:
1. Lowercase output with no terminal period — capitalize first letter,
append "." if missing.
2. Hallucinated "' clusters Whisper inserts when it interprets a
fragment as quoted dialogue (cora, ivan, atlas, hope had these).
Strip everywhere; never legitimate English punctuation.
3. Trailing apostrophe-then-period (.'.) from earlier rounds where a
closing-quoted line got an extra "." appended — collapse to single
terminal. Function is now idempotent.
Adds --from-cache flag: skip ASR, re-apply normalize from cached
whisper_refs.json. No GPU needed, useful after tuning the normalizer.
Lazy-imports torch so --from-cache works on any host.
Affects 9 of 40 voices: clara, grace, hazel, iris, felix, hugo
(lowercase fix); cora, ivan, atlas, hope (quote-cluster fix).
F5-TTS cloning quality depends on ref_text matching the prosody of ref_audio
(commas, periods, casing). Previous ref_texts were LibriSpeech ground-truth
labels: ALL CAPS, no punctuation — wrong signal for a flow-matching TTS
conditioned on text. Whisper hears what F5 will hear.
- scripts/whisper_refs.py — transcribe all wavs, rewrite
voice_to_speaker.default.yaml + cloned-voices/voices_metadata.json
in place. Also writes cloned-voices/whisper_refs.json sidecar.
- Makefile: whisper-refs target. Idempotent, rerun whenever
cloned-voices/ changes.
Run on a GPU host (4090/3090). ~30s for 40 short clips on a 4090.
