zerobench_eval/scorers.py

"""Self-contained metric implementations for ZeroBench-TTS.

No TTS model is ever loaded here — this module only reads finished wavs and
scores them:

    WER    two ASRs (openai/whisper-large-v3 + vinai/PhoWhisper-large), min taken,
           against the expanded reference set from ``references.py``
    SSIM   cosine similarity of microsoft/wavlm-base-plus-sv x-vectors between
           the generated clip and the benchmark's reference clip
    UTMOS  UTMOSv2 naturalness MOS (optional — see ``UTMOSScorer``)
    SIL    excess leading / trailing / mid-utterance silence, in seconds

Everything loads once per process and is reused across items.
"""

from __future__ import annotations

import re
import unicodedata

import numpy as np

DEFAULT_ASR = ("openai/whisper-large-v3", "vinai/PhoWhisper-large")

#: Reference policies, in reporting order. See ``score_all_policies``.
POLICIES = ("strict", "norm", "robust")


# ── text normalization + WER ──────────────────────────────────────────────────

def normalize_for_cer(text: str) -> str:
    """lowercase, NFC-normalize, strip punctuation, collapse whitespace."""
    text = unicodedata.normalize("NFC", text.lower())
    text = re.sub(r"[^\w\s]", "", text, flags=re.UNICODE)
    text = re.sub(r"\s+", " ", text).strip()
    return text


def _levenshtein_seq(a, b) -> int:
    if a == b:
        return 0
    if not a:
        return len(b)
    if not b:
        return len(a)
    prev = list(range(len(b) + 1))
    for i, ca in enumerate(a, 1):
        cur = [i] + [0] * len(b)
        for j, cb in enumerate(b, 1):
            cur[j] = min(prev[j] + 1, cur[j - 1] + 1, prev[j - 1] + (0 if ca == cb else 1))
        prev = cur
    return prev[-1]


def word_error_rate(hyp: str, ref: str) -> float:
    """WER = edit_distance(words) / len(ref_words), clamped to [0, 1]. Callers
    normalize with :func:`normalize_for_cer` first."""
    ref_words, hyp_words = ref.split(), hyp.split()
    if not ref_words:
        return 0.0 if not hyp_words else 1.0
    try:
        import jiwer
        m = jiwer.process_words(ref, hyp)
        dist = m.substitutions + m.deletions + m.insertions
    except ImportError:
        dist = _levenshtein_seq(hyp_words, ref_words)
    return float(min(max(dist / len(ref_words), 0.0), 1.0))


def score_wer_flat(pred: str, references: list[str]) -> tuple[float, str]:
    """min WER over an explicit list of whole-sentence references."""
    hyp = normalize_for_cer(pred)
    best, best_ref = 1.0, references[0] if references else ""
    for ref in references:
        if not ref:
            continue
        w = word_error_rate(hyp, normalize_for_cer(ref))
        if w < best:
            best, best_ref = w, ref
    return best, best_ref


def score_all_policies(transcripts: dict[str, str], text: str,
                       text_normalized: str = "") -> dict:
    """WER of every ASR transcript under all three reference policies.

    ``transcripts`` maps an ASR label -> its transcript of the same clip.

    Returns ``wer_<policy>`` (min across ASRs — the reported number),
    ``wer_<policy>_<asr>`` per ASR, and which ASR / reference won ``robust``.
    """
    from .references import best_wer

    normalized = text_normalized if text_normalized and text_normalized != text else ""
    out: dict = {}
    winners: dict[str, tuple[float, str, str]] = {}

    for policy in POLICIES:
        per_asr: dict[str, tuple[float, str]] = {}
        for label, hyp in transcripts.items():
            if policy == "strict":
                wer, ref = score_wer_flat(hyp, [text])
            elif policy == "norm":
                wer, ref = score_wer_flat(hyp, [text] + ([normalized] if normalized else []))
            else:
                wer, ref = best_wer(hyp, text, [normalized] if normalized else [])
            per_asr[label] = (wer, ref)
            out[f"wer_{policy}_{label}"] = round(wer, 6)
        label = min(per_asr, key=lambda k: per_asr[k][0])
        wer, ref = per_asr[label]
        out[f"wer_{policy}"] = round(wer, 6)
        winners[policy] = (wer, ref, label)

    out["wer"] = out["wer_robust"]                       # headline
    out["wer_matched_reference"] = winners["robust"][1]
    out["wer_matched_asr"] = winners["robust"][2]
    return out


# ── ASR ───────────────────────────────────────────────────────────────────────

def asr_label(model_id: str) -> str:
    """Short, column-safe name for an ASR checkpoint."""
    tail = model_id.split("/")[-1].lower()
    if "phowhisper" in tail:
        return "pho"
    if "whisper-large-v3" in tail:
        return "wlv3"
    return re.sub(r"[^0-9a-z]+", "_", tail).strip("_")


class WhisperTranscriber:
    """Any Whisper-family checkpoint from `transformers`."""

    def __init__(self, model_id: str = "openai/whisper-large-v3", device: str = "cuda"):
        import torch
        from transformers import WhisperForConditionalGeneration, WhisperProcessor

        self.torch = torch
        self.device = torch.device(device)
        self.processor = WhisperProcessor.from_pretrained(model_id)
        dtype = torch.float16 if self.device.type == "cuda" else torch.float32
        self.model = (WhisperForConditionalGeneration
                      .from_pretrained(model_id, torch_dtype=dtype)
                      .to(self.device).eval())
        for p in self.model.parameters():
            p.requires_grad = False

    def transcribe(self, wav_16k: np.ndarray, lang: str | None = "vi") -> str:
        with self.torch.no_grad():
            feats = self.processor(wav_16k, sampling_rate=16_000, return_tensors="pt")
            feats = feats.input_features.to(self.device, dtype=self.model.dtype)
            forced = (self.processor.get_decoder_prompt_ids(language=lang, task="transcribe")
                      if lang else None)
            ids = self.model.generate(feats, forced_decoder_ids=forced, max_new_tokens=256)
        return self.processor.batch_decode(ids, skip_special_tokens=True)[0].strip()


# ── speaker similarity ────────────────────────────────────────────────────────

class SSIMScorer:
    """Cosine similarity between WavLM-SV x-vectors of generated and reference audio."""

    def __init__(self, model_id: str = "microsoft/wavlm-base-plus-sv", device: str = "cuda"):
        import torch
        from transformers import WavLMForXVector, Wav2Vec2FeatureExtractor

        self.torch = torch
        self.device = torch.device(device)
        self.extractor = Wav2Vec2FeatureExtractor.from_pretrained(model_id)
        self.model = WavLMForXVector.from_pretrained(model_id).to(self.device).eval()
        for p in self.model.parameters():
            p.requires_grad = False

    def embed(self, wav_16k: np.ndarray) -> np.ndarray:
        with self.torch.no_grad():
            inputs = self.extractor(wav_16k, sampling_rate=16_000, return_tensors="pt")
            inputs = {k: v.to(self.device) for k, v in inputs.items()}
            return self.model(**inputs).embeddings.squeeze(0).float().cpu().numpy()

    def score(self, pred_wav_16k: np.ndarray, ref_wav_16k: np.ndarray) -> float:
        a, b = self.embed(pred_wav_16k), self.embed(ref_wav_16k)
        return float(np.dot(a, b) / (np.linalg.norm(a) * np.linalg.norm(b) + 1e-8))


# ── naturalness ───────────────────────────────────────────────────────────────

UTMOS_INSTALL_HINT = (
    "UTMOSv2 is not installed. It is an optional dependency (WER and SSIM work "
    "without it):\n"
    "    pip install git+https://github.com/sarulab-speech/UTMOSv2.git\n"
    "Or pass --skip_utmos to report NaN for the UTMOS column."
)


class UTMOSScorer:
    """UTMOSv2 naturalness MOS. Optional — see :data:`UTMOS_INSTALL_HINT`.

    UTMOSv2 ensembles over randomly sampled spectrogram crops, so an unseeded
    call is NOT reproducible: scoring one clip three times in a row returns
    e.g. 3.05 / 3.03 / 2.96. A benchmark number that moves between runs is not
    a benchmark number, so the RNG is reset to ``seed`` before every clip. That
    makes UTMOS a deterministic function of the audio, which is what lets two
    people scoring the same wavs get the same figure.
    """

    def __init__(self, device: str = "cuda", seed: int = 42):
        try:
            import utmosv2
        except ImportError as e:                       # pragma: no cover
            raise ImportError(UTMOS_INSTALL_HINT) from e
        self.model = utmosv2.create_model(pretrained=True)
        self.seed = seed

    def _reseed(self) -> None:
        import random

        import torch
        random.seed(self.seed)
        np.random.seed(self.seed)
        torch.manual_seed(self.seed)
        if torch.cuda.is_available():
            torch.cuda.manual_seed_all(self.seed)

    def score(self, wav_16k: np.ndarray) -> float:
        self._reseed()
        mos = self.model.predict(data=wav_16k, sr=16_000)
        if hasattr(mos, "item"):
            return float(mos.item())
        if isinstance(mos, (list, np.ndarray)):
            return float(mos[0])
        return float(mos)


# ── silence hygiene (no model) ────────────────────────────────────────────────

class SilenceScorer:
    """How much *unwanted* silence a clip carries — long lead-in, long tail, long
    internal pauses.

    Nothing in WER/SSIM/UTMOS penalizes dead air: an ASR happily transcribes a
    clip that opens with 1.5 s of nothing, the x-vector is unaffected, and UTMOS
    rates the audio quality of silence as fine. ``librosa.effects.split`` gates
    frame energy at ``top_db`` below the clip's own peak; whatever it drops is
    silence. ``excess_silence`` ignores the silence a natural utterance is
    allowed (``max_edge_sec`` per end, ``max_mid_sec`` per internal pause).
    """

    def __init__(self, top_db: float = 35.0, frame_length: int = 1024,
                 hop_length: int = 256, max_edge_sec: float = 0.1,
                 max_mid_sec: float = 0.3):
        self.top_db = top_db
        self.frame_length = frame_length
        self.hop_length = hop_length
        self.max_edge_sec = max_edge_sec
        self.max_mid_sec = max_mid_sec

    def score(self, wav_16k: np.ndarray, sr: int = 16_000) -> dict:
        import librosa

        wav = np.asarray(wav_16k, dtype=np.float32).reshape(-1)
        dur = len(wav) / sr
        dead = {"lead_silence": dur, "trail_silence": 0.0, "max_mid_silence": 0.0,
                "total_mid_silence": 0.0, "excess_silence": dur,
                "speech_duration": 0.0, "duration": dur}
        if (len(wav) < self.frame_length or not np.any(np.isfinite(wav))
                or float(np.abs(wav).max()) <= 0.0):
            return dead

        intervals = librosa.effects.split(wav, top_db=self.top_db,
                                          frame_length=self.frame_length,
                                          hop_length=self.hop_length)
        if len(intervals) == 0:
            return dead

        lead = float(intervals[0][0]) / sr
        trail = float(len(wav) - intervals[-1][1]) / sr
        gaps = [float(intervals[k][0] - intervals[k - 1][1]) / sr
                for k in range(1, len(intervals))]
        excess = (max(0.0, lead - self.max_edge_sec) + max(0.0, trail - self.max_edge_sec)
                  + sum(max(0.0, g - self.max_mid_sec) for g in gaps))
        return {
            "lead_silence": lead, "trail_silence": trail,
            "max_mid_silence": max(gaps) if gaps else 0.0,
            "total_mid_silence": float(sum(gaps)),
            "excess_silence": excess,
            "speech_duration": float(sum(e - s for s, e in intervals)) / sr,
            "duration": dur,
        }


# ── audio io ──────────────────────────────────────────────────────────────────

def load_wav_16k(path: str) -> np.ndarray:
    """Read any wav as mono float32 at 16 kHz."""
    import soundfile as sf

    wav, sr = sf.read(str(path), dtype="float32", always_2d=False)
    wav = np.asarray(wav, dtype=np.float32)
    if wav.ndim > 1:
        wav = wav.mean(axis=1)
    return resample_to_16k(wav.reshape(-1), sr)


def resample_to_16k(wav: np.ndarray, sr: int) -> np.ndarray:
    if sr == 16_000:
        return wav.astype(np.float32)
    try:
        import torch
        import torchaudio
        t = torch.from_numpy(wav.astype(np.float32)).unsqueeze(0)
        return torchaudio.functional.resample(t, sr, 16_000).squeeze(0).numpy()
    except ImportError:
        import librosa
        return librosa.resample(wav.astype(np.float32), orig_sr=sr, target_sr=16_000)


# ── the bundle ────────────────────────────────────────────────────────────────

class MetricSuite:
    """Loads every scorer once. Instantiate a single time per process."""

    def __init__(self, device: str = "cuda", asr_models=DEFAULT_ASR,
                 skip_utmos: bool = False, silence_top_db: float = 35.0,
                 silence_max_edge_sec: float = 0.1, silence_max_mid_sec: float = 0.3):
        self.asr: dict[str, WhisperTranscriber] = {}
        for model_id in asr_models:
            print(f"[zerobench] loading ASR {model_id} ...", flush=True)
            self.asr[asr_label(model_id)] = WhisperTranscriber(model_id, device=device)
        print("[zerobench] loading SSIM (WavLM-SV) ...", flush=True)
        self.ssim = SSIMScorer(device=device)
        self.utmos = None
        if not skip_utmos:
            print("[zerobench] loading UTMOS (UTMOSv2) ...", flush=True)
            self.utmos = UTMOSScorer(device=device)
        self.silence = SilenceScorer(top_db=silence_top_db,
                                     max_edge_sec=silence_max_edge_sec,
                                     max_mid_sec=silence_max_mid_sec)

    def score(self, pred_wav_16k: np.ndarray, ref_wav_16k: np.ndarray,
              text: str, text_normalized: str = "", lang: str = "vi") -> dict:
        transcripts = {label: a.transcribe(pred_wav_16k, lang=lang)
                       for label, a in self.asr.items()}
        sil = self.silence.score(pred_wav_16k, 16_000)
        return {
            **{f"transcript_{k}": v for k, v in transcripts.items()},
            **score_all_policies(transcripts, text, text_normalized),
            "ssim": self.ssim.score(pred_wav_16k, ref_wav_16k),
            "utmos": self.utmos.score(pred_wav_16k) if self.utmos else float("nan"),
            "excess_silence": sil["excess_silence"],
            "lead_silence": sil["lead_silence"],
            "trail_silence": sil["trail_silence"],
            "max_mid_silence": sil["max_mid_silence"],
            "duration_sec": len(pred_wav_16k) / 16_000,
        }