scripts/convert_audio.py

#!/usr/bin/env python3
"""
Convert Kanade decoder and HiFT vocoder to CoreML.

These are non-autoregressive models (single forward pass), so conversion
is simpler than the LLM — no KV cache or StateType needed.

Two models are produced:
- KanadeDecoder.mlpackage: audio token indices + speaker embedding → mel spectrogram
- HiFTVocoder.mlpackage: mel spectrogram → PCM waveform

Usage:
    python scripts/convert_kanade.py [--output-dir PATH] [--num-tokens 100]
"""

import argparse
from pathlib import Path

import numpy as np
import torch
import torch.nn as nn
import torch.nn.functional as F
import coremltools as ct
from kanade_tokenizer import KanadeModel, load_vocoder
import kanade_tokenizer.module.transformer as kanade_transformer


# ── Monkey-patch Kanade's complex RoPE with real-valued version ───────────

def _apply_rotary_emb_real(x: torch.Tensor, freqs_cis: torch.Tensor) -> torch.Tensor:
    """Real-valued RoPE replacement for Kanade's complex-number version.
    Converts complex freqs_cis to cos/sin and applies split-half rotation.
    """
    # freqs_cis is complex: (seq_len, head_dim/2)
    cos = freqs_cis.real  # (seq_len, head_dim/2)
    sin = freqs_cis.imag
    # Broadcast to match x shape: (bsz, seq_len, n_heads, head_dim)
    # x has head_dim, cos/sin have head_dim/2 — need to double them
    cos = torch.cat([cos, cos], dim=-1)  # (seq_len, head_dim)
    sin = torch.cat([sin, sin], dim=-1)
    # Reshape for broadcast: (1, seq_len, 1, head_dim)
    cos = cos.unsqueeze(0).unsqueeze(2)
    sin = sin.unsqueeze(0).unsqueeze(2)
    # Split-half rotation
    half = x.shape[-1] // 2
    x1 = x[..., :half]
    x2 = x[..., half:]
    rotated = torch.cat((-x2, x1), dim=-1)
    return (x * cos + rotated * sin).type_as(x)


def _apply_rotary_emb_precomputed(x: torch.Tensor, freqs_cos_sin: torch.Tensor) -> torch.Tensor:
    """Real-valued RoPE using precomputed cos/sin stored as (seq_len, head_dim).

    Matches Kanade's INTERLEAVED complex multiplication:
      view_as_complex(x.reshape(..., -1, 2)) * (cos + i*sin)
    which pairs adjacent elements: (x0,x1), (x2,x3), ...

    Equivalent real-valued form:
      out[2k]   = x[2k]*cos[k] - x[2k+1]*sin[k]
      out[2k+1] = x[2k]*sin[k] + x[2k+1]*cos[k]

    head_dim is always 64, so we have 32 pairs.
    """
    # freqs_cos_sin: (seq_len, 64) where [:32] = cos, [32:] = sin
    cos = freqs_cos_sin[..., :32]  # (seq_len, 32)
    sin = freqs_cos_sin[..., 32:]  # (seq_len, 32)
    # Broadcast: (1, seq_len, 1, 32)
    cos = cos.unsqueeze(0).unsqueeze(2)
    sin = sin.unsqueeze(0).unsqueeze(2)

    # Interleaved pairs: x has shape (..., 64), pair as (..., 32, 2)
    x_pairs = x.reshape(*x.shape[:-1], 32, 2)  # (..., 32, 2)
    x_even = x_pairs[..., 0]  # (..., 32)
    x_odd = x_pairs[..., 1]   # (..., 32)

    # Complex multiply: (x_even + i*x_odd) * (cos + i*sin)
    out_even = x_even * cos - x_odd * sin
    out_odd = x_even * sin + x_odd * cos

    # Interleave back: stack on last dim then flatten
    out = torch.stack([out_even, out_odd], dim=-1)  # (..., 32, 2)
    out = out.reshape(*x.shape)  # (..., 64)
    return out.type_as(x)


def _patched_attention_forward_v2(self, x, freqs_cis, mask, return_kv=False):
    """Attention forward with real-valued RoPE and explicit matmul.
    Supports local (windowed) attention via additive -inf mask.
    """
    bsz, seqlen, _ = x.shape
    xq, xk, xv = self.wq(x), self.wk(x), self.wv(x)

    xq = xq.view(bsz, seqlen, self.n_heads, self.head_dim)
    xk = xk.view(bsz, seqlen, self.n_heads, self.head_dim)
    xv = xv.view(bsz, seqlen, self.n_heads, self.head_dim)

    if freqs_cis is not None:
        xq = _apply_rotary_emb_precomputed(xq, freqs_cis[:seqlen])
        xk = _apply_rotary_emb_precomputed(xk, freqs_cis[:seqlen])

    xq = xq.transpose(1, 2)
    xk = xk.transpose(1, 2)
    xv = xv.transpose(1, 2)

    attn_weights = torch.matmul(xq, xk.transpose(2, 3)) * self.scale

    # Build attention mask (causal + local window)
    if self.causal or self.use_local_attention or mask is not None:
        attn_mask = torch.zeros((seqlen, seqlen), device=x.device, dtype=x.dtype)
        if self.causal:
            causal = torch.triu(
                torch.full((seqlen, seqlen), float("-inf"), device=x.device, dtype=x.dtype),
                diagonal=1,
            )
            attn_mask = attn_mask + causal
        if self.use_local_attention:
            # Block positions outside the window [-window_per_side, +window_per_side]
            local_mask = torch.triu(
                torch.full((seqlen, seqlen), float("-inf"), device=x.device, dtype=x.dtype),
                diagonal=self.window_per_side + 1,
            ) + torch.tril(
                torch.full((seqlen, seqlen), float("-inf"), device=x.device, dtype=x.dtype),
                diagonal=-(self.window_per_side + 1),
            )
            attn_mask = attn_mask + local_mask
        attn_weights = attn_weights + attn_mask
    if mask is not None:
        attn_weights = attn_weights + mask

    attn_weights = F.softmax(attn_weights, dim=-1, dtype=torch.float32).to(xq.dtype)
    output = torch.matmul(attn_weights, xv)

    # 12 heads * 64 head_dim = 768
    output = output.transpose(1, 2).contiguous().reshape(bsz, seqlen, 768)
    output = self.wo(output)

    if return_kv:
        return output, (xk, xv)
    return output


def _convert_freqs_cis_to_real(transformer_module):
    """Replace complex freqs_cis buffer with real-valued cos/sin concatenation."""
    if hasattr(transformer_module, 'freqs_cis') and transformer_module.freqs_cis is not None:
        fc = transformer_module.freqs_cis  # (max_len, head_dim/2) complex
        cos = fc.real.float()  # (max_len, head_dim/2)
        sin = fc.imag.float()
        real_freqs = torch.cat([cos, sin], dim=-1)  # (max_len, head_dim)
        # Replace the buffer
        del transformer_module.freqs_cis
        transformer_module.register_buffer('freqs_cis', real_freqs)


def patch_kanade_for_coreml(kanade: KanadeModel):
    """Apply monkey-patches to make Kanade traceable by coremltools."""
    kanade_transformer.Attention.forward = _patched_attention_forward_v2
    # Convert complex freqs_cis to real in all transformers
    for name, module in kanade.named_modules():
        if isinstance(module, kanade_transformer.Transformer):
            _convert_freqs_cis_to_real(module)


class KanadeDecoderWrapper(nn.Module):
    """Wraps Kanade's decode pipeline for tracing.

    Pipeline: token indices → quantizer decode → mel_prenet → upsample →
              mel_decoder (conditioned on speaker) → mel_postnet → mel
    """

    def __init__(self, kanade: KanadeModel, num_tokens: int):
        super().__init__()
        self.local_quantizer = kanade.local_quantizer
        self.mel_prenet = kanade.mel_prenet
        self.mel_conv_upsample = kanade.mel_conv_upsample
        self.mel_decoder = kanade.mel_decoder
        self.mel_postnet = kanade.mel_postnet
        self.num_tokens = num_tokens
        # Precompute mel_length for this token count
        self.mel_length = kanade._calculate_target_mel_length(
            kanade._calculate_original_audio_length(num_tokens)
        )

    def forward(
        self,
        token_indices: torch.Tensor,
        speaker_embedding: torch.Tensor,
    ) -> torch.Tensor:
        """
        Args:
            token_indices: (num_tokens,) int32 — Kanade codebook indices (0-12799)
            speaker_embedding: (1, 128) float32 — speaker embedding

        Returns:
            mel: (1, 80, mel_length) float32
        """
        # Quantizer decode: indices → content embedding
        content_emb = self.local_quantizer.decode(token_indices)  # (num_tokens, 768)
        content_emb = content_emb.unsqueeze(0)  # (1, num_tokens, 768)

        # Mel prenet (transformer)
        local_latent = self.mel_prenet(content_emb)

        # Upsample to mel length
        if self.mel_conv_upsample is not None:
            local_latent = self.mel_conv_upsample(
                local_latent.transpose(1, 2)
            ).transpose(1, 2)
        local_latent = F.interpolate(
            local_latent.transpose(1, 2), size=self.mel_length, mode="linear"
        ).transpose(1, 2)

        # Mel decoder (conditioned on speaker)
        mel = self.mel_decoder(local_latent, condition=speaker_embedding.unsqueeze(1))
        mel = mel.transpose(1, 2)  # (1, 80, mel_length)

        # Postnet
        mel = self.mel_postnet(mel)
        return mel


class FullVocoderWrapper(nn.Module):
    """Complete mel → waveform pipeline: F0 prediction + source gen + HiFT decode + iSTFT.

    Noise is replaced with zeros for deterministic tracing.
    """

    def __init__(self, vocoder, num_stft_frames: int):
        super().__init__()
        self.vocoder = vocoder
        self.num_stft_frames = num_stft_frames
        n_fft = vocoder.istft_n_fft  # 16
        hop_len = vocoder.istft_hop_len  # 4

        # iDFT basis
        n = torch.arange(n_fft, dtype=torch.float32)
        k = torch.arange(n_fft, dtype=torch.float32)
        angles = 2.0 * torch.pi * n.unsqueeze(1) * k.unsqueeze(0) / n_fft
        self.register_buffer("idft_cos", torch.cos(angles) / n_fft)
        self.register_buffer("idft_sin", torch.sin(angles) / n_fft)
        self.register_buffer("window", vocoder.stft_window.clone())

        # Source generation constants
        self.sampling_rate = vocoder.m_source.l_sin_gen.sampling_rate
        self.harmonic_num = vocoder.m_source.l_sin_gen.harmonic_num  # 8
        self.sine_amp = vocoder.m_source.l_sin_gen.sine_amp  # 0.1
        self.upsample_scale = vocoder.m_source.l_sin_gen.upsample_scale  # 480

        # Harmonic multipliers: [1, 2, ..., 9]
        self.register_buffer(
            "harmonic_muls",
            torch.arange(1, self.harmonic_num + 2, dtype=torch.float32),
        )

        # l_linear and l_tanh from m_source
        self.source_linear = vocoder.m_source.l_linear
        self.source_tanh = vocoder.m_source.l_tanh

        self.n_fft = n_fft
        self.hop_len = hop_len
        self.n_fft_half = n_fft // 2 + 1

    def _generate_source(self, f0: torch.Tensor) -> torch.Tensor:
        """f0: (1, mel_length) → source_stft: (1, 18, stft_frames)"""
        # Upsample f0: (1, mel_length) → (1, 1, mel_length) → nearest → (1, 1, audio_length)
        f0_up = F.interpolate(
            f0.unsqueeze(1), scale_factor=float(self.upsample_scale), mode="nearest"
        ).squeeze(1)  # (1, audio_length)

        # Generate harmonics: f0 * [1..9]
        # f0_up: (1, L) → (1, L, 1) * (9,) → (1, L, 9)
        fn = f0_up.unsqueeze(-1) * self.harmonic_muls.unsqueeze(0).unsqueeze(0)

        # Phase accumulation: cumsum(f/sr) * 2pi
        rad = (fn / self.sampling_rate)  # instantaneous frequency in cycles per sample
        phase = torch.cumsum(rad, dim=1) * 2.0 * torch.pi  # (1, L, 9)

        # Sine waves
        sines = torch.sin(phase) * self.sine_amp  # (1, L, 9)

        # UV mask (voiced/unvoiced)
        uv = (f0_up > 0).float().unsqueeze(-1)  # (1, L, 1)

        # Apply UV (no noise — zeros instead of randn for tracing)
        sines = sines * uv  # (1, L, 9)

        # l_linear + tanh: (1, L, 9) → linear → (1, L, 1) → tanh
        source = self.source_tanh(self.source_linear(sines))  # (1, L, 1)
        source = source.squeeze(-1)  # (1, L)

        # Manual STFT (torch.stft/unfold not CoreML-compatible)
        # n_fft=16, hop=4. With center padding, we get num_stft_frames frames.
        # Pad source: reflect pad n_fft//2 on each side
        padded = F.pad(source, (self.n_fft // 2, self.n_fft // 2), mode="reflect")
        # padded: (1, L + n_fft) where L = audio_length

        # Extract overlapping frames using conv1d with identity kernel
        # This replaces unfold: conv1d with (n_fft, 1, n_fft) identity kernel, stride=hop
        # Equivalent to: frames[i] = padded[i*hop : i*hop + n_fft]
        eye_kernel = torch.eye(self.n_fft, dtype=source.dtype, device=source.device).unsqueeze(1)
        # padded: (1, L+16) → (1, 1, L+16) for conv1d
        frames = F.conv1d(padded.unsqueeze(1), eye_kernel, stride=self.hop_len)
        # frames: (1, 16, num_frames)
        frames = frames * self.window.unsqueeze(0).unsqueeze(-1)  # window each frame
        # Transpose to (1, num_frames, 16) for matmul
        frames = frames.transpose(1, 2)

        # DFT via matmul
        dft_cos = self.idft_cos[:self.n_fft_half, :] * self.n_fft  # undo 1/N normalization
        dft_sin = self.idft_sin[:self.n_fft_half, :] * self.n_fft
        s_real = torch.matmul(frames, dft_cos.T)   # (1, NF, 9)
        s_imag = -torch.matmul(frames, dft_sin.T)  # (1, NF, 9)
        source_stft = torch.cat([s_real.transpose(1, 2), s_imag.transpose(1, 2)], dim=1)
        return source_stft

    def _istft_overlap_add(self, x: torch.Tensor) -> torch.Tensor:
        """x: (1, 18, num_frames) conv_post output → waveform (1, samples)"""
        magnitude = torch.exp(x[:, :self.n_fft_half, :])
        phase = torch.sin(x[:, self.n_fft_half:, :])

        real_half = magnitude * torch.cos(phase)
        imag_half = magnitude * torch.sin(phase)

        real_mirror = torch.flip(real_half[:, 1:self.n_fft_half - 1, :], dims=[1])
        imag_mirror = -torch.flip(imag_half[:, 1:self.n_fft_half - 1, :], dims=[1])
        real_full = torch.cat([real_half, real_mirror], dim=1)
        imag_full = torch.cat([imag_half, imag_mirror], dim=1)

        real_t = real_full.transpose(1, 2)
        imag_t = imag_full.transpose(1, 2)
        segments = torch.matmul(real_t, self.idft_cos.T) - torch.matmul(imag_t, self.idft_sin.T)

        NF = self.num_stft_frames
        segments = segments * self.window.unsqueeze(0).unsqueeze(0)
        seg = segments.squeeze(0)
        seg_chunks = seg.reshape(NF, 4, 4)

        b0 = seg_chunks[:, 0, :].reshape(-1)
        b1 = seg_chunks[:, 1, :].reshape(-1)
        b2 = seg_chunks[:, 2, :].reshape(-1)
        b3 = seg_chunks[:, 3, :].reshape(-1)

        F4 = NF * 4
        padded_samples = NF * 4 + 12
        output = torch.zeros(padded_samples)
        output[0:F4] = output[0:F4] + b0
        output[4:F4 + 4] = output[4:F4 + 4] + b1
        output[8:F4 + 8] = output[8:F4 + 8] + b2
        output[12:F4 + 12] = output[12:F4 + 12] + b3

        win_sq = self.window * self.window
        win_chunks = win_sq.reshape(4, 4)
        w0 = win_chunks[0].repeat(NF)
        w1 = win_chunks[1].repeat(NF)
        w2 = win_chunks[2].repeat(NF)
        w3 = win_chunks[3].repeat(NF)

        wnorm = torch.zeros(padded_samples)
        wnorm[0:F4] = wnorm[0:F4] + w0
        wnorm[4:F4 + 4] = wnorm[4:F4 + 4] + w1
        wnorm[8:F4 + 8] = wnorm[8:F4 + 8] + w2
        wnorm[12:F4 + 12] = wnorm[12:F4 + 12] + w3

        output = output / (wnorm + 1e-8)
        pad = 8
        trimmed_len = (NF - 1) * 4
        output = output[pad:pad + trimmed_len]
        output = torch.clamp(output, -0.99, 0.99)
        return output.unsqueeze(0)

    def forward(self, mel: torch.Tensor) -> torch.Tensor:
        """mel: (1, 80, T) → waveform: (1, samples)"""
        # F0 prediction
        f0 = self.vocoder.f0_predictor(mel)  # (1, T)

        # Source generation
        source_stft = self._generate_source(f0)

        # HiFT decode
        x = self.vocoder.conv_pre(mel)
        for i in range(self.vocoder.num_upsamples):
            x = F.leaky_relu(x, self.vocoder.lrelu_slope)
            x = self.vocoder.ups[i](x)
            if i == self.vocoder.num_upsamples - 1:
                x = self.vocoder.reflection_pad(x)
            si = self.vocoder.source_downs[i](source_stft)
            si = self.vocoder.source_resblocks[i](si)
            x = x + si
            xs = None
            for j in range(self.vocoder.num_kernels):
                if xs is None:
                    xs = self.vocoder.resblocks[i * self.vocoder.num_kernels + j](x)
                else:
                    xs += self.vocoder.resblocks[i * self.vocoder.num_kernels + j](x)
            x = xs / self.vocoder.num_kernels

        x = F.leaky_relu(x)
        x = self.vocoder.conv_post(x)

        return self._istft_overlap_add(x)


class F0PredictorWrapper(nn.Module):
    """Wraps HiFT's f0 predictor: mel → f0."""

    def __init__(self, vocoder):
        super().__init__()
        self.f0_predictor = vocoder.f0_predictor

    def forward(self, mel: torch.Tensor) -> torch.Tensor:
        """mel: (1, 80, T) → f0: (1, 1, T)"""
        return self.f0_predictor(mel)


class HiFTDecodeWrapper(nn.Module):
    """Wraps HiFT's decode stage: mel + source_stft → waveform.

    Includes a manual iSTFT implementation using matmul with a precomputed
    DFT basis matrix, so the entire pipeline runs inside CoreML.
    """

    def __init__(self, vocoder, num_stft_frames: int):
        super().__init__()
        self.vocoder = vocoder
        self.num_stft_frames = num_stft_frames  # hardcoded for tracing
        n_fft = vocoder.istft_n_fft  # 16
        hop_len = vocoder.istft_hop_len  # 4

        # Precompute DFT basis for iSTFT: (n_fft, n_fft) real-valued IDFT matrix
        # X[k] = sum_n x[n] * exp(j*2pi*n*k/N) → x[n] = (1/N) * sum_k X[k] * exp(j*2pi*n*k/N)
        n = torch.arange(n_fft, dtype=torch.float32)
        k = torch.arange(n_fft, dtype=torch.float32)
        angles = 2.0 * torch.pi * n.unsqueeze(1) * k.unsqueeze(0) / n_fft  # (n_fft, n_fft)
        # cos/sin basis for real/imag parts
        self.register_buffer("idft_cos", torch.cos(angles) / n_fft)  # (n_fft, n_fft)
        self.register_buffer("idft_sin", torch.sin(angles) / n_fft)  # (n_fft, n_fft)

        # Window for overlap-add
        self.register_buffer("window", vocoder.stft_window.clone())
        self.n_fft = n_fft
        self.hop_len = hop_len
        self.n_fft_half = n_fft // 2 + 1  # 9

    def forward(self, mel: torch.Tensor, source_stft: torch.Tensor) -> torch.Tensor:
        """
        Args:
            mel: (1, 80, T) float32
            source_stft: (1, 18, T') float32 — real+imag STFT of source signal

        Returns:
            waveform: (1, samples) float32
        """
        x = self.vocoder.conv_pre(mel)
        for i in range(self.vocoder.num_upsamples):
            x = F.leaky_relu(x, self.vocoder.lrelu_slope)
            x = self.vocoder.ups[i](x)
            if i == self.vocoder.num_upsamples - 1:
                x = self.vocoder.reflection_pad(x)

            si = self.vocoder.source_downs[i](source_stft)
            si = self.vocoder.source_resblocks[i](si)
            x = x + si

            xs = None
            for j in range(self.vocoder.num_kernels):
                if xs is None:
                    xs = self.vocoder.resblocks[i * self.vocoder.num_kernels + j](x)
                else:
                    xs += self.vocoder.resblocks[i * self.vocoder.num_kernels + j](x)
            x = xs / self.vocoder.num_kernels

        x = F.leaky_relu(x)
        x = self.vocoder.conv_post(x)  # (1, 18, num_frames)

        # Split into magnitude and phase
        magnitude = torch.exp(x[:, :self.n_fft_half, :])  # (1, 9, num_frames)
        phase = torch.sin(x[:, self.n_fft_half:, :])       # (1, 9, num_frames)

        # Convert to real/imag
        real_half = magnitude * torch.cos(phase)  # (1, 9, num_frames)
        imag_half = magnitude * torch.sin(phase)

        # Mirror to full spectrum (Hermitian symmetry)
        # real: [r0, r1, ..., r8, r7, r6, ..., r1]
        # imag: [i0, i1, ..., i8, -i7, -i6, ..., -i1]
        real_mirror = torch.flip(real_half[:, 1:self.n_fft_half - 1, :], dims=[1])
        imag_mirror = -torch.flip(imag_half[:, 1:self.n_fft_half - 1, :], dims=[1])
        real_full = torch.cat([real_half, real_mirror], dim=1)  # (1, 16, num_frames)
        imag_full = torch.cat([imag_half, imag_mirror], dim=1)  # (1, 16, num_frames)

        # iDFT via matmul: output[n] = sum_k (real[k]*cos[n,k] - imag[k]*sin[n,k])
        # (1, 16, num_frames) → transpose to (1, num_frames, 16) → matmul with (16, 16)
        real_t = real_full.transpose(1, 2)  # (1, num_frames, 16)
        imag_t = imag_full.transpose(1, 2)
        # segments[n] = sum_k real[k]*cos[n,k] - imag[k]*sin[n,k]
        # = real_t @ idft_cos.T - imag_t @ idft_sin.T
        # But idft_cos is (n_fft, n_fft) where idft_cos[n,k] = cos(2pi*n*k/N)/N
        # We want segments[frame, n] = sum_k (real[frame,k] * idft_cos[n,k] - imag[frame,k] * idft_sin[n,k])
        # = (real_t @ idft_cos^T - imag_t @ idft_sin^T)[frame, n]
        segments = torch.matmul(real_t, self.idft_cos.T) - torch.matmul(imag_t, self.idft_sin.T)
        # segments: (1, num_frames, 16)

        # Overlap-add with window
        # n_fft=16, hop=4, so overlap ratio = 4 (each sample covered by 4 frames)
        NF = self.num_stft_frames  # hardcoded constant for tracing
        segments = segments * self.window.unsqueeze(0).unsqueeze(0)  # (1, NF, 16)
        seg = segments.squeeze(0)  # (NF, 16)

        # Reshape each 16-sample segment into 4 chunks of 4 (hop_len) samples
        # seg: (F, 16) → (F, 4, 4)
        seg_chunks = seg.reshape(NF, 4, 4)  # (F, 4_blocks, 4_samples)

        # Block b of frame f lands at output position (f + b) * hop_len
        # Rearrange so block b from all frames is contiguous:
        # chunk_b[f] = seg_chunks[f, b, :] lands at output[(f+b)*4 : (f+b)*4 + 4]
        # = output index f*4 + b*4 ... but shifted by b frames
        # Equivalently: for block b, we have F values that go to positions b, b+1, ..., b+F-1
        # in units of hop_len

        # For each sub-block offset (0..3), create a flat array and add shifted
        # Using static slicing only — no dynamic indexing
        padded_samples = NF * 4 + 12  # (NF-1)*4 + 16
        # Actually: (num_frames - 1) * 4 + 16 = num_frames * 4 + 12

        # Each sub-block b contributes F chunks of 4 samples, placed at positions
        # starting from b*4 with stride 4 between frames.
        # block_b = seg_chunks[:, b, :].reshape(-1) → F*4 contiguous values
        # These go to output[b*4 : b*4 + F*4]
        b0 = seg_chunks[:, 0, :].reshape(-1)  # (F*4,) → output[0 : F*4]
        b1 = seg_chunks[:, 1, :].reshape(-1)  # (F*4,) → output[4 : F*4 + 4]
        b2 = seg_chunks[:, 2, :].reshape(-1)  # (F*4,) → output[8 : F*4 + 8]
        b3 = seg_chunks[:, 3, :].reshape(-1)  # (F*4,) → output[12 : F*4 + 12]

        F4 = NF * 4
        output = torch.zeros(padded_samples)
        output[0:F4] = output[0:F4] + b0
        output[4:F4 + 4] = output[4:F4 + 4] + b1
        output[8:F4 + 8] = output[8:F4 + 8] + b2
        output[12:F4 + 12] = output[12:F4 + 12] + b3

        # Window normalization — same structure
        win_sq = self.window * self.window  # (16,)
        win_chunks = win_sq.reshape(4, 4)  # (4_blocks, 4_samples)
        w0 = win_chunks[0].repeat(NF)
        w1 = win_chunks[1].repeat(NF)
        w2 = win_chunks[2].repeat(NF)
        w3 = win_chunks[3].repeat(NF)

        wnorm = torch.zeros(padded_samples)
        wnorm[0:F4] = wnorm[0:F4] + w0
        wnorm[4:F4 + 4] = wnorm[4:F4 + 4] + w1
        wnorm[8:F4 + 8] = wnorm[8:F4 + 8] + w2
        wnorm[12:F4 + 12] = wnorm[12:F4 + 12] + w3

        output = output / (wnorm + 1e-8)

        # Trim center padding: n_fft//2 = 8 from start
        pad = 8
        trimmed_len = (NF - 1) * 4  # expected output length
        output = output[pad:pad + trimmed_len]
        output = torch.clamp(output, -0.99, 0.99)
        return output.unsqueeze(0)  # (1, samples)


def convert_kanade_decoder(kanade: KanadeModel, num_tokens: int, output_dir: Path):
    """Convert Kanade decoder to CoreML."""
    wrapper = KanadeDecoderWrapper(kanade, num_tokens).eval().float()
    print(f"Tracing Kanade decoder (num_tokens={num_tokens}, mel_length={wrapper.mel_length})...")

    token_indices = torch.arange(num_tokens, dtype=torch.int32)
    speaker_embedding = torch.randn(1, 128, dtype=torch.float32)

    with torch.no_grad():
        # Test forward
        mel = wrapper(token_indices, speaker_embedding)
        print(f"  Output mel shape: {mel.shape}")

        traced = torch.jit.trace(wrapper, (token_indices, speaker_embedding))

    print("Converting Kanade decoder to CoreML...")
    mlmodel = ct.convert(
        traced,
        inputs=[
            ct.TensorType(name="token_indices", shape=(num_tokens,), dtype=np.int32),
            ct.TensorType(name="speaker_embedding", shape=(1, 128), dtype=np.float32),
        ],
        outputs=[ct.TensorType(name="mel", dtype=np.float32)],
        compute_precision=ct.precision.FLOAT32,
        minimum_deployment_target=ct.target.iOS17,
    )

    out_path = output_dir / "KanadeDecoder.mlpackage"
    mlmodel.save(str(out_path))
    print(f"Saved Kanade decoder to {out_path}")


def convert_f0_predictor(vocoder, mel_length: int, output_dir: Path):
    """Convert HiFT f0 predictor to CoreML."""
    wrapper = F0PredictorWrapper(vocoder).eval().float()
    print(f"Tracing F0 predictor (mel_length={mel_length})...")

    mel = torch.randn(1, 80, mel_length, dtype=torch.float32)

    with torch.no_grad():
        f0 = wrapper(mel)
        print(f"  Output f0 shape: {f0.shape}")
        traced = torch.jit.trace(wrapper, (mel,))

    print("Converting F0 predictor to CoreML...")
    mlmodel = ct.convert(
        traced,
        inputs=[
            ct.TensorType(name="mel", shape=(1, 80, mel_length), dtype=np.float32),
        ],
        outputs=[ct.TensorType(name="f0", dtype=np.float32)],
        compute_precision=ct.precision.FLOAT32,
        minimum_deployment_target=ct.target.iOS17,
    )

    out_path = output_dir / "F0Predictor.mlpackage"
    mlmodel.save(str(out_path))
    print(f"Saved F0 predictor to {out_path}")


def convert_hift_decode(vocoder, mel_length: int, output_dir: Path):
    """Convert HiFT decode stage to CoreML.

    Source signal STFT must be computed externally (Swift side).
    """
    # Compute source_stft shape: run f0 predictor + source module to get it
    mel = torch.randn(1, 80, mel_length, dtype=torch.float32)
    with torch.no_grad():
        f0 = vocoder.f0_predictor(mel)
        s = vocoder.f0_upsamp(f0[:, None]).transpose(1, 2)
        s, _, _ = vocoder.m_source(s)
        s = s.transpose(1, 2)
        s_stft_real, s_stft_imag = vocoder._stft(s.squeeze(1))
        source_stft = torch.cat([s_stft_real, s_stft_imag], dim=1)
        num_stft_frames = source_stft.shape[2]
        print(f"  Source STFT shape: {source_stft.shape} ({num_stft_frames} frames)")

    wrapper = HiFTDecodeWrapper(vocoder, num_stft_frames).eval().float()

    print(f"Tracing HiFT decode (mel_length={mel_length})...")
    with torch.no_grad():
        waveform = wrapper(mel, source_stft)
        print(f"  Output waveform shape: {waveform.shape}")
        traced = torch.jit.trace(wrapper, (mel, source_stft))

    print("Converting HiFT decode to CoreML...")
    source_stft_channels = source_stft.shape[1]
    source_stft_time = source_stft.shape[2]
    mlmodel = ct.convert(
        traced,
        inputs=[
            ct.TensorType(name="mel", shape=(1, 80, mel_length), dtype=np.float32),
            ct.TensorType(
                name="source_stft",
                shape=(1, source_stft_channels, source_stft_time),
                dtype=np.float32,
            ),
        ],
        outputs=[ct.TensorType(name="waveform", dtype=np.float32)],
        compute_precision=ct.precision.FLOAT32,
        minimum_deployment_target=ct.target.iOS17,
    )

    out_path = output_dir / "HiFTDecode.mlpackage"
    mlmodel.save(str(out_path))
    print(f"Saved HiFT decode to {out_path}")


def main():
    parser = argparse.ArgumentParser(description="Convert Kanade + HiFT to CoreML")
    parser.add_argument(
        "--output-dir", type=str,
        default=str(Path(__file__).parent.parent),
        help="Output directory",
    )
    parser.add_argument(
        "--num-tokens", type=int, default=100,
        help="Fixed number of audio tokens (determines mel length)",
    )
    args = parser.parse_args()
    convert_audio(Path(args.output_dir), args.num_tokens)


def convert_audio(output_dir: Path, num_tokens: int = 100) -> tuple[Path, Path]:
    """Convert Kanade decoder + HiFT vocoder to CoreML.

    Returns (KanadeDecoder.mlpackage, Vocoder.mlpackage) paths."""
    output_dir.mkdir(parents=True, exist_ok=True)

    print("Loading Kanade model...")
    kanade = KanadeModel.from_pretrained("frothywater/kanade-25hz-clean").eval().float()
    patch_kanade_for_coreml(kanade)
    vocoder = load_vocoder(kanade.config.vocoder_name).eval().float()

    mel_length = kanade._calculate_target_mel_length(
        kanade._calculate_original_audio_length(num_tokens)
    )

    print(f"\n=== Converting Kanade decoder ===")
    convert_kanade_decoder(kanade, num_tokens, output_dir)

    print(f"\n=== Converting full vocoder (mel → waveform) ===")
    convert_full_vocoder(vocoder, mel_length, output_dir)

    print("\nAudio conversion complete!")
    print(f"  KanadeDecoder: {num_tokens} tokens → mel (80, {mel_length})")
    print(f"  Vocoder: mel (80, {mel_length}) → waveform")
    return output_dir / "KanadeDecoder.mlpackage", output_dir / "Vocoder.mlpackage"


def convert_full_vocoder(vocoder, mel_length: int, output_dir: Path):
    """Convert complete mel→waveform vocoder to CoreML."""
    # Get num_stft_frames by running a dummy forward
    mel = torch.randn(1, 80, mel_length, dtype=torch.float32)
    with torch.no_grad():
        f0 = vocoder.f0_predictor(mel)
        s = vocoder.f0_upsamp(f0[:, None]).transpose(1, 2)
        s, _, _ = vocoder.m_source(s)
        s = s.transpose(1, 2)
        sr, si = vocoder._stft(s.squeeze(1))
        num_stft_frames = sr.shape[2]
        print(f"  STFT frames: {num_stft_frames}")

    wrapper = FullVocoderWrapper(vocoder, num_stft_frames).eval().float()

    print(f"Tracing full vocoder (mel_length={mel_length})...")
    # Replace randn_like with zeros for tracing
    orig_randn = torch.randn_like
    torch.randn_like = lambda x, **kw: torch.zeros_like(x)
    with torch.no_grad():
        wav = wrapper(mel)
        print(f"  Output waveform: {wav.shape}")
        traced = torch.jit.trace(wrapper, (mel,))
    torch.randn_like = orig_randn

    print("Converting full vocoder to CoreML...")
    mlmodel = ct.convert(
        traced,
        inputs=[ct.TensorType(name="mel", shape=(1, 80, mel_length), dtype=np.float32)],
        outputs=[ct.TensorType(name="waveform", dtype=np.float32)],
        compute_precision=ct.precision.FLOAT32,
        minimum_deployment_target=ct.target.iOS17,
    )

    out_path = output_dir / "Vocoder.mlpackage"
    mlmodel.save(str(out_path))
    print(f"Saved vocoder to {out_path}")


if __name__ == "__main__":
    main()