feat: add config-driven extraction and audio sync tooling

Makefile

@@ -0,0 +1,83 @@
+VENV ?= .venv
+PY := $(VENV)/bin/python
+PIP := $(PY) -m pip
+UV := uv
+CONFIG ?= config.toml
+
+# detect uv, fallback to pip
+HAS_UV := $(shell command -v $(UV) >/dev/null 2>&1 && echo 1 || echo 0)
+ifeq ($(HAS_UV),1)
+  VENV_CREATE = $(UV) venv $(VENV) --python 3.11 2>/dev/null || $(UV) venv $(VENV)
+  PIP_INSTALL = $(UV) pip install --python $(PY)
+else
+  VENV_CREATE = python3 -m venv $(VENV)
+  PIP_INSTALL = $(PIP) install
+endif
+
+.PHONY: install install-cpu install-rocm install-cuda extract ast clean help
+
+help:
+	@echo "Targets:"
+	@echo "  make install        # auto-detect GPU (ROCm>CUDA>CPU) via rocm-smi/nvidia-smi/torch, create venv, install deps"
+	@echo "  make install-cpu    # force CPU torch"
+	@echo "  make install-rocm   # force ROCm torch (RX 7900 XTX gfx1100)"
+	@echo "  make install-cuda   # force CUDA torch"
+	@echo "  make extract        # run extract.py (uses config.toml if present)"
+	@echo "  make ast            # run sync_audio_test.py (audio_sync_test, PyQtGraph GUI)"
+	@echo "  make clean"
+
+install:
+	@if [ ! -d $(VENV) ]; then echo "=> creating venv $(VENV)"; $(VENV_CREATE); else echo "=> venv exists $(VENV)"; fi
+	@echo "=> detecting GPU..."
+	@HAS_ROCM=0; HAS_CUDA=0; \
+	if command -v rocm-smi >/dev/null 2>&1 && [ -c /dev/kfd ] && lspci 2>/dev/null | grep -qi amd; then HAS_ROCM=1; fi; \
+	if command -v nvidia-smi >/dev/null 2>&1; then HAS_CUDA=1; fi; \
+	if [ $$HAS_ROCM -eq 1 ]; then \
+		echo "   ROCm detected (AMD) -> torch rocm6.2"; \
+		$(PIP_INSTALL) --upgrade pip; \
+		$(PIP_INSTALL) torch torchaudio --index-url https://download.pytorch.org/whl/rocm6.2; \
+	elif [ $$HAS_CUDA -eq 1 ]; then \
+		echo "   CUDA detected (NVIDIA) -> torch cu121"; \
+		$(PIP_INSTALL) --upgrade pip; \
+		$(PIP_INSTALL) torch torchaudio --index-url https://download.pytorch.org/whl/cu121; \
+	else \
+		echo "   No GPU -> torch cpu"; \
+		$(PIP_INSTALL) --upgrade pip; \
+		$(PIP_INSTALL) torch torchaudio --index-url https://download.pytorch.org/whl/cpu; \
+	fi
+	@echo "=> installing common deps..."
+	@$(PIP_INSTALL) soundfile scipy numpy pyqtgraph PyQt6
+	@echo "=> optional sounddevice (audio playback, volume slider)..."
+	@$(PIP_INSTALL) sounddevice || echo "   sounddevice optional failed (PortAudio missing) -> playback disabled"
+	@$(PY) -c "import torch, sys; print(f'torch {torch.__version__} cuda_available={torch.cuda.is_available()}', end=''); print(f' device={torch.cuda.get_device_name(0)}' if torch.cuda.is_available() else ' (cpu)')"
+	@echo "=> done. Activate: source $(VENV)/bin/activate"
+
+install-cpu:
+	@if [ ! -d $(VENV) ]; then $(VENV_CREATE); fi
+	$(PIP_INSTALL) --upgrade pip
+	$(PIP_INSTALL) torch torchaudio --index-url https://download.pytorch.org/whl/cpu
+	$(PIP_INSTALL) soundfile scipy numpy pyqtgraph PyQt6 sounddevice || true
+	$(PY) -c "import torch; print(torch.__version__, torch.cuda.is_available())"
+
+install-rocm:
+	@if [ ! -d $(VENV) ]; then $(VENV_CREATE); fi
+	$(PIP_INSTALL) --upgrade pip
+	$(PIP_INSTALL) torch torchaudio --index-url https://download.pytorch.org/whl/rocm6.2
+	$(PIP_INSTALL) soundfile scipy numpy pyqtgraph PyQt6 sounddevice || true
+	$(PY) -c "import torch; print(torch.__version__, torch.cuda.is_available(), torch.cuda.get_device_name(0) if torch.cuda.is_available() else '')"
+
+install-cuda:
+	@if [ ! -d $(VENV) ]; then $(VENV_CREATE); fi
+	$(PIP_INSTALL) --upgrade pip
+	$(PIP_INSTALL) torch torchaudio --index-url https://download.pytorch.org/whl/cu121
+	$(PIP_INSTALL) soundfile scipy numpy pyqtgraph PyQt6 sounddevice || true
+	$(PY) -c "import torch; print(torch.__version__, torch.cuda.is_available(), torch.cuda.get_device_name(0) if torch.cuda.is_available() else '')"
+
+extract:
+	@if [ -x $(PY) ]; then $(PY) extract.py; else python3 extract.py; fi
+
+ast:
+	@if [ -x $(PY) ]; then $(PY) sync_audio_test.py --config $(CONFIG); else python3 sync_audio_test.py --config $(CONFIG); fi
+
+clean:
+	rm -rf $(VENV) __pycache__ .pytest_cache

config.toml

@@ -0,0 +1,28 @@
+# movie_sync base config — shared by extract.py and sync_audio_test.py
+# TOML is efficient: no yaml dep, stdlib tomllib (py3.11+) parses directly.
+
+[extract]
+# Input files — relative to repo root or absolute. Same as extract.py inputs.
+file_a = "/home/honney/Videos/Drachenzähmen/Drachenzaehmen.mp4"
+file_b = "/home/honney/Videos/Drachenzähmen/How to Train Your Dragon.mkv"
+# Window to extract (seconds). This is the ONLY duration needed.
+duration = 90
+# Start offset in file (seconds, 0 = file start). ffmpeg -ss before -i for fast seek.
+start = 0.0
+out_dir = "extracted"
+target_fps = "24000/1001"   # Blu-ray film 23.976
+target_fps_eps = 0.02
+
+[audio]
+# Target for re-encode / load. Must be identical for both files.
+sample_rate = 48000
+channels = 1
+# If extracted wavs already exist, sync test can load them directly:
+# file_a_wav = "extracted/Drachenzaehmen_audio.wav"
+# file_b_wav = "extracted/How to Train Your Dragon_audio.wav"
+
+[sync]
+# Analysis window: null = use full extracted duration; otherwise limit for quick test
+# duration = 30  # optional, seconds, null = full
+method = "phat"   # "phat" (GCC-PHAT, robust) or "standard" (raw)
+use_gpu = "auto"  # "auto" | "cpu" | "cuda" (ROCm/CUDA both via torch.cuda)

extract.py

@@ -12,16 +12,53 @@ import os
 import sys
 import shutil
 
-# ─── Hardcoded input (relative to this script's directory) ───
+# ─── Input / config (config.toml is base config, fallback to hardcoded) ───
-inputs = [
+CONFIG_PATH = os.path.join(os.path.dirname(os.path.abspath(__file__)), "config.toml")
-    "/home/honney/Videos/Drachenzähmen/Drachenzaehmen.mp4",
+_cfg_inputs = None
-    "/home/honney/Videos/Drachenzähmen/How to Train Your Dragon.mkv"
+_cfg_duration = 90
-]
+_cfg_start = 0.0
+_cfg_out_dir = os.path.join(os.path.dirname(os.path.abspath(__file__)), "extracted")
+_cfg_target_fps = "24000/1001"
+_cfg_eps = 0.02
+try:
+    try:
+        import tomllib  # py3.11+
+    except ModuleNotFoundError:
+        import tomli as tomllib  # type: ignore
+    if os.path.exists(CONFIG_PATH):
+        with open(CONFIG_PATH, "rb") as _f:
+            _cfg = tomllib.load(_f)
+        _ex = _cfg.get("extract", {})
+        if _ex.get("file_a") or _ex.get("file_b"):
+            _cfg_inputs = [p for p in [_ex.get("file_a"), _ex.get("file_b")] if p]
+        _cfg_duration = int(_ex.get("duration", _cfg_duration))
+        _cfg_start = float(_ex.get("start", _cfg_start))
+        _cfg_out_dir = _ex.get("out_dir", _cfg_out_dir)
+        if _ex.get("target_fps"):
+            _cfg_target_fps = str(_ex["target_fps"])
+        if _ex.get("target_fps_eps") is not None:
+            try:
+                _cfg_eps = float(_ex["target_fps_eps"])
+            except Exception:
+                pass
+        if _cfg_inputs:
+            print(f"[config] loaded {CONFIG_PATH}: duration={_cfg_duration}s start={_cfg_start}s target_fps={_cfg_target_fps}")
+except Exception as _e:
+    print(f"[config] warn: failed to load {CONFIG_PATH}: {_e}", file=sys.stderr)
+
+if _cfg_inputs is not None:
+    inputs = _cfg_inputs
+else:
+    inputs = [
+        "/home/honney/Videos/Drachenzähmen/Drachenzaehmen.mp4",
+        "/home/honney/Videos/Drachenzähmen/How to Train Your Dragon.mkv"
+    ]
 INPUT_FILES = []
 for input_file in inputs:
     INPUT_FILES.append(os.path.join(os.path.dirname(os.path.abspath(__file__)), input_file))
-DURATION   = 90  # 1.5 minutes in seconds
+DURATION   = _cfg_duration
-OUT_DIR    = os.path.join(os.path.dirname(os.path.abspath(__file__)), "extracted")
+START_SEC  = _cfg_start  # for ffmpeg -ss (0 = file start)
+OUT_DIR    = os.path.join(os.path.dirname(os.path.abspath(__file__)), _cfg_out_dir) if not os.path.isabs(_cfg_out_dir) else _cfg_out_dir
 
 # ─── Analysis-friendly codecs (NOT GPU) ───
 # Video: FFV1 (lossless, intra-only) in MKV. Every frame stands alone, no
@@ -39,9 +76,14 @@ OUT_DIR    = os.path.join(os.path.dirname(os.path.abspath(__file__)), "extracted
 #   of 90 s clips is fast enough and bit-exact.
 VIDEO_CODEC_BASE = ["-c:v", "ffv1", "-level", "3", "-pix_fmt", "yuv444p"]
 AUDIO_CODEC = ["-c:a", "pcm_f32le", "-ar", "48000", "-ac", "1"]
-TARGET_FPS = "24000/1001"            # Blu-ray film = 23.976023... (shown as 23.98)
+# target fps may be overridden via config.toml
-TARGET_FPS_FLOAT = 24000 / 1001
+TARGET_FPS = _cfg_target_fps  # default "24000/1001"
-FPS_EPS = 0.02                        # tolerance for float comparison
+try:
+    _n, _d = TARGET_FPS.split("/") if "/" in TARGET_FPS else (TARGET_FPS, "1")
+    TARGET_FPS_FLOAT = float(_n) / float(_d)
+except Exception:
+    TARGET_FPS_FLOAT = 24000 / 1001
+FPS_EPS = _cfg_eps  # tolerance for float comparison
 
 def _parse_rate(s: str) -> float | None:
     s = s.strip()
@@ -135,9 +177,11 @@ for INPUT_FILE in INPUT_FILES:
         if not needs_fps:
             video_codec = VIDEO_CODEC_BASE + ["-vf", f"fps={TARGET_FPS}:round=near", "-fps_mode", "cfr"]
 
+    ss_args = ["-ss", str(START_SEC)] if START_SEC and START_SEC != 0 else []
     cmd_video = [
         "ffmpeg",
         "-y",               # overwrite output
+        *ss_args,           # seek before -i (fast, frame-accurate with re-encode)
         "-i", INPUT_FILE,
         "-t", str(DURATION),
         "-an",              # no audio
@@ -154,6 +198,7 @@ for INPUT_FILE in INPUT_FILES:
     cmd_audio = [
         "ffmpeg",
         "-y",
+        *ss_args,
         "-i", INPUT_FILE,
         "-t", str(DURATION),
         "-vn",              # no video

sync_audio.py

@@ -0,0 +1,217 @@
+#!/usr/bin/env python3
+"""
+Audio cross-correlation for movie_sync — torch GPU auto (ROCm/CUDA) with CPU fallback.
+
+Content-to-content sync (Option A): ignores container start_time/edit-list mux delay.
+If audio is delayed in container, we pad with silence on mux instead of shifting presentation.
+Extracted wavs are pcm_f32le 48k mono (extract.py:41), so correlation is phase-accurate.
+
+Usage:
+  from sync_audio import load_wav, correlate, find_lag
+  a, sr = load_wav("extracted/Drachenzaehmen_audio.wav")
+  lag_samples, peak, corr = correlate(a, b, sr=48000, method="phat", device="auto")
+"""
+
+from __future__ import annotations
+import os
+import sys
+import math
+from typing import Tuple, Literal
+
+import numpy as np
+
+try:
+    import soundfile as sf  # preferred for f32 wav
+    HAS_SF = True
+except ImportError:
+    HAS_SF = False
+
+try:
+    import torch
+    HAS_TORCH = True
+except ImportError:
+    HAS_TORCH = False
+
+
+def _get_device(pref: str = "auto") -> str:
+    if pref == "cpu":
+        return "cpu"
+    if pref in ("cuda", "auto") and HAS_TORCH and torch.cuda.is_available():
+        return "cuda"
+    return "cpu"
+
+
+def load_wav(path: str, target_sr: int = 48000, mono: bool = True) -> Tuple[np.ndarray, int]:
+    """Load wav as float32 mono. Resample if needed (cheap linear warn)."""
+    if not os.path.exists(path):
+        raise FileNotFoundError(path)
+    if HAS_SF:
+        data, sr = sf.read(path, always_2d=False, dtype="float32")
+    else:
+        # fallback scipy
+        from scipy.io import wavfile
+        sr, data = wavfile.read(path)
+        if data.dtype == np.int16:
+            data = data.astype(np.float32) / 32768.0
+        elif data.dtype == np.int32:
+            data = data.astype(np.float32) / 2147483648.0
+        elif data.dtype != np.float32:
+            data = data.astype(np.float32)
+    if data.ndim > 1:
+        if mono:
+            data = data.mean(axis=1).astype(np.float32)
+    if sr != target_sr:
+        # simple resample via scipy if available, else warn
+        try:
+            from scipy.signal import resample_poly
+            import math as _m
+            g = _m.gcd(sr, target_sr)
+            data = resample_poly(data, target_sr // g, sr // g).astype(np.float32)
+            sr = target_sr
+        except Exception:
+            print(f"WARNING: {path} sr={sr} != {target_sr} and resample failed, using as-is", file=sys.stderr)
+    return data.astype(np.float32), sr
+
+
+def _next_pow2(n: int) -> int:
+    return 1 << (n - 1).bit_length()
+
+
+def _normalize(a: np.ndarray) -> np.ndarray:
+    a = a - a.mean()
+    s = a.std()
+    return a / s if s > 1e-9 else a
+
+
+def correlate(
+    a: np.ndarray,
+    b: np.ndarray,
+    sr: int = 48000,
+    method: Literal["phat", "standard"] = "phat",
+    device: str = "auto",
+    normalize: bool = True,
+) -> Tuple[int, float, np.ndarray]:
+    """
+    Return (lag_samples, peak_value, corr_array).
+    lag >0 means b delayed vs a (b starts later), need to shift b earlier by lag.
+    Convention: corr = ifft(FFT(a) * conj(FFT(b))). peak at lag = argmax.
+    GPU via torch if available, else numpy.
+    """
+    if normalize:
+        a = _normalize(a)
+        b = _normalize(b)
+
+    n = len(a) + len(b) - 1
+    N = _next_pow2(n)
+
+    dev = _get_device(device)
+
+    if dev == "cuda" and HAS_TORCH:
+        # torch path — ROCm and CUDA both via cuda device
+        try:
+            ta = torch.from_numpy(a).to("cuda", dtype=torch.float32)
+            tb = torch.from_numpy(b).to("cuda", dtype=torch.float32)
+            Fa = torch.fft.rfft(ta, n=N)
+            Fb = torch.fft.rfft(tb, n=N)
+            R = Fa * torch.conj(Fb)
+            if method == "phat":
+                R = R / (torch.abs(R) + 1e-10)
+            corr_t = torch.fft.irfft(R, n=N)
+            # fftshift to center 0 lag
+            corr_t = torch.roll(corr_t, shifts=N // 2)
+            corr = corr_t.cpu().numpy()
+            # keep only valid length n centered
+            start = N // 2 - (len(b) - 1)
+            # Actually after roll, we want slice; simpler: use raw without roll and map lag later
+            # Recompute without roll for correct indexing, keep roll for display but fix lag calc
+            # For lag calc we need not shift: peak at N - lag etc. So we use shifted version + offset mapping
+            # To avoid confusion, return shifted corr and map lag accordingly
+            peak_idx = int(np.argmax(np.abs(corr)))
+            # lag = peak_idx - (len(b)-1) - (N//2 - (len(b)-1))? Let's instead use unshifted for lag and shifted for display
+            # Fallback: compute lag from unshifted
+            corr_raw = torch.fft.irfft(R, n=N).cpu().numpy()
+            peak_raw = int(np.argmax(np.abs(corr_raw)))
+            # raw layout: lag 0 at 0, positive lag (b delayed) wraps to end
+            if peak_raw > N // 2:
+                lag = peak_raw - N
+            else:
+                lag = peak_raw
+            peak_val = float(np.abs(corr_raw[peak_raw]))
+            # return shifted display corr + lag
+            return lag, peak_val, corr
+        except Exception as e:
+            print(f"torch cuda failed ({e}), falling back cpu", file=sys.stderr)
+            dev = "cpu"
+
+    # numpy/scipy cpu path
+    Fa = np.fft.rfft(a, n=N)
+    Fb = np.fft.rfft(b, n=N)
+    R = Fa * np.conj(Fb)
+    if method == "phat":
+        R = R / (np.abs(R) + 1e-10)
+    corr_raw = np.fft.irfft(R, n=N)
+    peak_raw = int(np.argmax(np.abs(corr_raw)))
+    if peak_raw > N // 2:
+        lag = peak_raw - N
+    else:
+        lag = peak_raw
+    peak_val = float(np.abs(corr_raw[peak_raw]))
+    # shifted for display centered at 0
+    corr_shifted = np.fft.fftshift(corr_raw)
+    # but we return raw shifted centered? Provide shifted for plotting
+    # For consistency with torch branch we return shifted display array
+    return lag, peak_val, corr_shifted
+
+
+def lag_to_seconds(lag_samples: int, sr: int = 48000) -> float:
+    return lag_samples / float(sr)
+
+
+def apply_lag_with_silence(wav: np.ndarray, lag_samples: int) -> np.ndarray:
+    """
+    Apply lag by padding silence at start (no sound for delay).
+    lag >0: b delayed vs a => pad b at start with lag silence to align to a, or trim a.
+    For mux: if lag>0 (b starts later), we need to delay a by lag or提前 b.
+    This helper pads with zeros (silence) at start; negative lag pads the other direction.
+    Caller decides which file to pad.
+    """
+    if lag_samples == 0:
+        return wav
+    if lag_samples > 0:
+        # b delayed => pad b front with lag silence to align to a
+        return np.concatenate([np.zeros(lag_samples, dtype=np.float32), wav])
+    else:
+        # b earlier => trim or pad a; this pads a-side: when applying to b, negative lag means b earlier, so we trim? Provide padded version for mux: pad with silence then trim alignment
+        # For generic helper: pad with silence at start if lag negative we pad other file, but this is applied to lagging file only
+        return np.concatenate([np.zeros(-lag_samples, dtype=np.float32), wav])
+
+
+# torch device info for Makefile / GUI
+def device_info() -> str:
+    if not HAS_TORCH:
+        return "torch not installed (cpu numpy)"
+    if torch.cuda.is_available():
+        try:
+            name = torch.cuda.get_device_name(0)
+        except Exception:
+            name = "cuda"
+        return f"torch {torch.__version__} + {name} (cuda/ROCm)"
+    return f"torch {torch.__version__} (cpu only)"
+
+
+if __name__ == "__main__":
+    import argparse, pathlib
+    ap = argparse.ArgumentParser()
+    ap.add_argument("a", help="wav A")
+    ap.add_argument("b", help="wav B")
+    ap.add_argument("--phat", action="store_true", help="use GCC-PHAT")
+    ap.add_argument("--device", default="auto", choices=["auto","cpu","cuda"])
+    ap.add_argument("--sr", type=int, default=48000)
+    args = ap.parse_args()
+    a, sa = load_wav(args.a, target_sr=args.sr)
+    b, sb = load_wav(args.b, target_sr=args.sr)
+    method = "phat" if args.phat else "standard"
+    lag, peak, _ = correlate(a, b, sr=args.sr, method=method, device=args.device)
+    print(f"device: {device_info()} method={method}")
+    print(f"lag_samples={lag} lag_sec={lag/args.sr:.6f}s peak={peak:.4f}")
+    print(f"apply: ffmpeg -i video.mkv -i audio.wav -filter_complex \"[1:a]adelay={max(0, lag/args.sr*1000):.0f}|{max(0, lag/args.sr*1000):.0f}[ad]\" -map 0:v -map \"[ad]\" out.mkv  (pad silence for delay)")

sync_audio_test.py

@@ -0,0 +1,415 @@
+#!/usr/bin/env python3
+"""
+PyQtGraph GUI to visualize audio cross-correlation and interactively tune lag.
+
+Features (per user request):
+ - uv venv via Makefile, torch auto GPU (ROCm/CUDA) with cpu fallback
+ - config.toml for file_a/file_b, duration/start (extract duration is source of truth)
+ - PyQtGraph waveforms (decimated for 4M samples) + xcorr plot
+ - QSlider + QDoubleSpinBox numeric entry for lag (seconds + samples)
+ - Volume slider (sounddevice optional, playback with lag applied, silence padded for delay)
+
+Run: make ast  or  .venv/bin/python sync_audio_test.py --config config.toml
+"""
+
+from __future__ import annotations
+import os, sys, math, argparse, pathlib
+import numpy as np
+
+# allow tomllib (py3.11+) with tomli fallback
+try:
+    import tomllib
+except ModuleNotFoundError:
+    import tomli as tomllib
+
+try:
+    import pyqtgraph as pg
+    from PyQt6 import QtWidgets, QtCore
+    HAS_PG = True
+except ImportError as e:
+    print("ERROR: pyqtgraph/PyQt6 not installed — run make install", file=sys.stderr)
+    print(e, file=sys.stderr)
+    sys.exit(1)
+
+try:
+    import soundfile as sf
+    HAS_SF = True
+except ImportError:
+    HAS_SF = False
+
+try:
+    import sounddevice as sd
+    HAS_SD = True
+except ImportError:
+    HAS_SD = False
+
+from sync_audio import load_wav, correlate, device_info, lag_to_seconds
+
+
+def load_config(path: str) -> dict:
+    if not os.path.exists(path):
+        return {}
+    with open(path, "rb") as f:
+        return tomllib.load(f)
+
+
+def decimate_for_plot(arr: np.ndarray, max_pts: int = 120_000) -> tuple[np.ndarray, int]:
+    if len(arr) <= max_pts:
+        return arr, 1
+    stride = int(math.ceil(len(arr) / max_pts))
+    return arr[::stride], stride
+
+
+def find_wavs_from_config(cfg: dict) -> tuple[str, str, int, float, float]:
+    audio_cfg = cfg.get("audio", {})
+    extract_cfg = cfg.get("extract", {})
+    sync_cfg = cfg.get("sync", {})
+    sr = int(audio_cfg.get("sample_rate", 48000))
+    # priority: explicit wav paths else derived from extracted dir
+    a_wav = audio_cfg.get("file_a_wav")
+    b_wav = audio_cfg.get("file_b_wav")
+    # fallback to extract files
+    out_dir = extract_cfg.get("out_dir", "extracted")
+    file_a = extract_cfg.get("file_a")
+    file_b = extract_cfg.get("file_b")
+    if not a_wav and file_a:
+        stem = os.path.splitext(os.path.basename(file_a))[0]
+        cand = os.path.join(out_dir, f"{stem}_audio.wav")
+        if os.path.exists(cand):
+            a_wav = cand
+        else:
+            a_wav = cand  # keep for error msg
+    if not b_wav and file_b:
+        stem = os.path.splitext(os.path.basename(file_b))[0]
+        cand = os.path.join(out_dir, f"{stem}_audio.wav")
+        if os.path.exists(cand):
+            b_wav = cand
+        else:
+            b_wav = cand
+    # also allow sync-specific override
+    duration = extract_cfg.get("duration", 90)
+    start = float(extract_cfg.get("start", 0.0))
+    # duration_sec comment: only duration needed is off the extract — we respect that
+    return a_wav, b_wav, sr, float(start), float(duration)
+
+
+class SyncWindow(QtWidgets.QMainWindow):
+    def __init__(self, a_path: str, b_path: str, sr: int = 48000, method: str = "phat", device: str = "auto"):
+        super().__init__()
+        self.setWindowTitle(f"movie_sync — audio sync test — {device_info()}")
+        self.resize(1400, 900)
+        self.a_path = a_path
+        self.b_path = b_path
+        self.sr = sr
+        self.method = method
+        self.device_pref = device
+        self._updating = False
+
+        # load
+        print(f"Loading {a_path}")
+        self.a, self.sr_a = load_wav(a_path, target_sr=sr)
+        print(f"Loading {b_path}")
+        self.b, self.sr_b = load_wav(b_path, target_sr=sr)
+        # keep originals for lag apply
+        self.a_orig = self.a.copy()
+        self.b_orig = self.b.copy()
+
+        # initial correlate
+        self.lag_samples, self.peak, self.corr = correlate(self.a, self.b, sr=sr, method=method, device=device)
+        self.lag_sec = self.lag_samples / sr
+        print(f"initial lag {self.lag_samples} samples = {self.lag_sec:.6f}s peak={self.peak:.4f}")
+
+        # decimated views
+        self.a_plot, self.stride_a = decimate_for_plot(self.a)
+        self.b_plot, self.stride_b = decimate_for_plot(self.b)
+        self.t_a = np.arange(len(self.a_plot)) * self.stride_a / sr
+        self.t_b = np.arange(len(self.b_plot)) * self.stride_b / sr
+
+        # xcorr display — corr is already fftshifted
+        N = len(self.corr)
+        # lags in seconds for display
+        # raw corr was shifted: center at N//2, range [- (len(b)-1) .. len(a)-1]
+        # for display we map indices to lag
+        total = len(self.a) + len(self.b) - 1
+        n_pow2 = N
+        # shifted lags: -N//2 .. N//2-1
+        self.corr_lags = np.arange(N) - N//2
+        self.corr_lags_sec = self.corr_lags / sr
+
+        central = QtWidgets.QWidget()
+        self.setCentralWidget(central)
+        lay = QtWidgets.QVBoxLayout(central)
+
+        # info bar
+        info = QtWidgets.QLabel(f"A: {os.path.basename(a_path)} ({len(self.a)/sr:.1f}s)  B: {os.path.basename(b_path)} ({len(self.b)/sr:.1f}s)  sr={sr}  method={method}  {device_info()}")
+        info.setWordWrap(True)
+        lay.addWidget(info)
+
+        # plots
+        self.gw = pg.GraphicsLayoutWidget()
+        lay.addWidget(self.gw, stretch=1)
+
+        # waveform A
+        self.p1 = self.gw.addPlot(row=0, col=0, title="Waveform A (reference)")
+        self.p1.showGrid(x=True, y=True)
+        self.p1.setLabel("bottom", "Time", "s")
+        self.curve_a = self.p1.plot(self.t_a, self.a_plot, pen=pg.mkPen("#4cc9f0", width=1))
+        self.p1.setMouseEnabled(x=True, y=False)
+
+        # waveform B with lag
+        self.p2 = self.gw.addPlot(row=1, col=0, title=f"Waveform B (shifted by lag)")
+        self.p2.showGrid(x=True, y=True)
+        self.p2.setLabel("bottom", "Time", "s")
+        self.curve_b = self.p2.plot(self.t_b, self.b_plot, pen=pg.mkPen("#f72585", width=1))
+        self.p2.setMouseEnabled(x=True, y=False)
+        # link x
+        self.p2.setXLink(self.p1)
+
+        # xcorr
+        self.p3 = self.gw.addPlot(row=2, col=0, title="Cross-correlation (GCC-PHAT)" if method=="phat" else "Cross-correlation")
+        self.p3.showGrid(x=True, y=True)
+        self.p3.setLabel("bottom", "Lag", "s")
+        # decimate corr for perf if huge
+        corr_dec, corr_stride = decimate_for_plot(self.corr, max_pts=200_000)
+        corr_lags_dec = self.corr_lags_sec[::corr_stride] if corr_stride>1 else self.corr_lags_sec
+        self.curve_corr = self.p3.plot(corr_lags_dec, np.abs(corr_dec), pen=pg.mkPen("#ffd166", width=1))
+        self.peak_line = pg.InfiniteLine(pos=self.lag_sec, angle=90, pen=pg.mkPen("#06d6a0", width=2, style=QtCore.Qt.PenStyle.DashLine))
+        self.p3.addItem(self.peak_line)
+        self.p3.setXRange(self.lag_sec-2, self.lag_sec+2)
+
+        # controls
+        ctr = QtWidgets.QHBoxLayout()
+        lay.addLayout(ctr)
+
+        ctr.addWidget(QtWidgets.QLabel("Lag (s):"))
+        self.slider = QtWidgets.QSlider(QtCore.Qt.Orientation.Horizontal)
+        self.slider.setRange(-10000, 10000)  # will map to seconds via scale
+        # range +/-10s in ms
+        self.slider.setMinimum(int(-10 * 1000))
+        self.slider.setMaximum(int(10 * 1000))
+        self.slider.setValue(int(self.lag_sec * 1000))
+        self.slider.setTickInterval(100)
+        ctr.addWidget(self.slider, stretch=1)
+
+        self.spin_sec = QtWidgets.QDoubleSpinBox()
+        self.spin_sec.setRange(-60, 60)
+        self.spin_sec.setDecimals(6)
+        self.spin_sec.setSingleStep(0.001)
+        self.spin_sec.setValue(self.lag_sec)
+        self.spin_sec.setSuffix(" s")
+        self.spin_sec.setKeyboardTracking(False)
+        ctr.addWidget(self.spin_sec)
+
+        self.spin_samp = QtWidgets.QSpinBox()
+        self.spin_samp.setRange(-10_000_000, 10_000_000)
+        self.spin_samp.setSingleStep(1)
+        self.spin_samp.setValue(self.lag_samples)
+        self.spin_samp.setSuffix(" samp")
+        ctr.addWidget(self.spin_samp)
+
+        btn_auto = QtWidgets.QPushButton("Auto peak")
+        ctr.addWidget(btn_auto)
+
+        btn_swap = QtWidgets.QPushButton("Swap A/B")
+        ctr.addWidget(btn_swap)
+
+        # volume + playback
+        ctr2 = QtWidgets.QHBoxLayout()
+        lay.addLayout(ctr2)
+        ctr2.addWidget(QtWidgets.QLabel("Volume:"))
+        self.vol = QtWidgets.QSlider(QtCore.Qt.Orientation.Horizontal)
+        self.vol.setRange(0, 100)
+        self.vol.setValue(70)
+        self.vol.setMaximumWidth(200)
+        ctr2.addWidget(self.vol)
+        self.vol_label = QtWidgets.QLabel("70%")
+        ctr2.addWidget(self.vol_label)
+
+        self.btn_play_a = QtWidgets.QPushButton("Play A (2s)")
+        self.btn_play_b = QtWidgets.QPushButton("Play B+lag (2s)")
+        self.btn_play_mix = QtWidgets.QPushButton("Play Mix")
+        self.btn_stop = QtWidgets.QPushButton("Stop")
+        for b in [self.btn_play_a, self.btn_play_b, self.btn_play_mix, self.btn_stop]:
+            ctr2.addWidget(b)
+        if not HAS_SD:
+            for b in [self.btn_play_a, self.btn_play_b, self.btn_play_mix, self.btn_stop]:
+                b.setEnabled(False)
+                b.setToolTip("sounddevice not installed — run make install (optional)")
+            ctr2.addWidget(QtWidgets.QLabel("(sounddevice missing — playback disabled)"))
+
+        self.ffmpeg_label = QtWidgets.QLabel()
+        self.ffmpeg_label.setWordWrap(True)
+        self.ffmpeg_label.setTextInteractionFlags(QtCore.Qt.TextInteractionFlag.TextSelectableByMouse)
+        lay.addWidget(self.ffmpeg_label)
+
+        # signals
+        self.slider.valueChanged.connect(self.on_slider)
+        self.spin_sec.valueChanged.connect(self.on_spin_sec)
+        self.spin_samp.valueChanged.connect(self.on_spin_samp)
+        self.vol.valueChanged.connect(lambda v: self.vol_label.setText(f"{v}%"))
+        btn_auto.clicked.connect(self.on_auto)
+        btn_swap.clicked.connect(self.on_swap)
+        self.btn_play_a.clicked.connect(lambda: self.play("a"))
+        self.btn_play_b.clicked.connect(lambda: self.play("b"))
+        self.btn_play_mix.clicked.connect(lambda: self.play("mix"))
+        self.btn_stop.clicked.connect(self.stop_play)
+
+        self.update_labels()
+
+    def _set_lag(self, lag_sec: float, source: str = ""):
+        if self._updating:
+            return
+        self._updating = True
+        lag_sec = float(np.clip(lag_sec, -60, 60))
+        lag_samp = int(round(lag_sec * self.sr))
+        self.lag_sec = lag_sec
+        self.lag_samples = lag_samp
+        # update widgets
+        self.slider.blockSignals(True); self.slider.setValue(int(lag_sec*1000)); self.slider.blockSignals(False)
+        self.spin_sec.blockSignals(True); self.spin_sec.setValue(lag_sec); self.spin_sec.blockSignals(False)
+        self.spin_samp.blockSignals(True); self.spin_samp.setValue(lag_samp); self.spin_samp.blockSignals(False)
+        self.peak_line.setPos(lag_sec)
+        # shift B curve visually by lag (pad with silence not needed for visualize, just shift x)
+        # we keep t_b but offset x
+        shift = lag_sec
+        # pyqtgraph setPos shifts items; we recreate x
+        # Instead shift data: plot t_b + lag
+        self.curve_b.setData(self.t_b + shift, self.b_plot)
+        self.update_labels()
+        self._updating = False
+
+    def update_labels(self):
+        # ffmpeg adelay for mux: add silence for delay (no sound for build-in delay)
+        # If lag>0: B delayed vs A => to mux B onto A video, delay B audio by lag (pad silence)
+        # adelay expects ms per channel, e.g. adelay=1234|1234
+        lag_ms = self.lag_sec * 1000
+        if lag_ms >= 0:
+            ffcmd = f'ffmpeg -i video.mkv -i audio.wav -filter_complex "[1:a]adelay={lag_ms:.0f}:all=1[ad]" -map 0:v -map "[ad]" -c:v copy -c:a pcm_s16le out.mkv'
+            note = f"B delayed by {self.lag_sec:.6f}s ({self.lag_samples} samp) → pad B start with silence {lag_ms:.0f} ms"
+        else:
+            # B earlier => pad A (or trim B). For adding B to A file, we need to delay video or pad A? Simplest pad A? But we control only audio: delay B negative means B earlier, so we delay A or use -itsoffset
+            note = f"B earlier by {abs(self.lag_sec):.6f}s → pad A / use -itsoffset {abs(lag_ms):.0f}ms or trim B by {abs(self.lag_samples)} samp"
+            ffcmd = f'# B early: ffmpeg -itsoffset {abs(lag_ms)/1000:.6f} -i audio.wav -i video.mkv ...  OR  pad video audio with silence'
+        self.ffmpeg_label.setText(f"{note}\n{ffcmd}")
+
+    # slots
+    def on_slider(self, v):
+        self._set_lag(v/1000.0, "slider")
+
+    def on_spin_sec(self, v):
+        self._set_lag(float(v), "sec")
+
+    def on_spin_samp(self, v):
+        self._set_lag(int(v)/self.sr, "samp")
+
+    def on_auto(self):
+        # recompute peak
+        lag, peak, corr = correlate(self.a_orig, self.b_orig, sr=self.sr, method=self.method, device=self.device_pref)
+        self.corr = corr
+        # update corr curve? re-decimate
+        self._set_lag(lag / self.sr, "auto")
+        print(f"auto lag {lag} samp {lag/self.sr:.6f}s peak={peak:.4f}")
+
+    def on_swap(self):
+        self.a_orig, self.b_orig = self.b_orig, self.a_orig
+        self.a, self.b = self.a_orig.copy(), self.b_orig.copy()
+        self.a_plot, _ = decimate_for_plot(self.a)
+        self.b_plot, _ = decimate_for_plot(self.b)
+        self.curve_a.setData(self.t_a, self.a_plot)
+        # recalc
+        lag, _, corr = correlate(self.a, self.b, sr=self.sr, method=self.method, device=self.device_pref)
+        self.corr = corr
+        self._set_lag(lag/self.sr, "swap")
+
+    def play(self, which: str):
+        if not HAS_SD:
+            return
+        vol = self.vol.value()/100.0
+        sr = self.sr
+        # play 2 seconds from 10s mark to hear sync
+        start_samp = int(10 * sr)
+        dur_samp = int(2 * sr)
+        if start_samp + dur_samp > len(self.a_orig):
+            start_samp = 0
+        a_seg = self.a_orig[start_samp:start_samp+dur_samp] * vol
+        # apply lag with silence padding (no sound for delay) — Option A
+        lag = self.lag_samples
+        # For playback mix, we need to align: if B delayed (lag>0), pad B front with silence
+        # For preview we shift B segment accordingly
+        b_start = start_samp
+        if lag > 0:
+            # B delayed => B segment should be taken earlier to align? For playback we pad B with lag silence, so effective B at time t is original at t-lag
+            idx = b_start - lag
+            if idx < 0:
+                b_seg = np.concatenate([np.zeros(-idx, dtype=np.float32), self.b_orig[0:b_start + dur_samp - (-idx) if b_start+dur_samp - (-idx)>0 else 0]])
+                # slice to dur
+                b_seg = b_seg[:dur_samp]
+                if len(b_seg) < dur_samp:
+                    b_seg = np.concatenate([b_seg, np.zeros(dur_samp-len(b_seg), dtype=np.float32)])
+            else:
+                b_seg = self.b_orig[idx:idx+dur_samp]
+        elif lag < 0:
+            idx = b_start - lag  # lag negative => plus
+            b_seg = self.b_orig[idx:idx+dur_samp] if idx+dur_samp < len(self.b_orig) else np.zeros(dur_samp, dtype=np.float32)
+            if len(b_seg) < dur_samp:
+                b_seg = np.concatenate([b_seg, np.zeros(dur_samp-len(b_seg), dtype=np.float32)])
+        else:
+            b_seg = self.b_orig[b_start:b_start+dur_samp]
+        b_seg = b_seg * vol
+        try:
+            sd.stop()
+            if which == "a":
+                sd.play(a_seg, samplerate=sr)
+            elif which == "b":
+                sd.play(b_seg, samplerate=sr)
+            elif which == "mix":
+                mix = (a_seg + b_seg) / 2.0
+                sd.play(mix, samplerate=sr)
+        except Exception as e:
+            print(f"playback failed {e}", file=sys.stderr)
+
+    def stop_play(self):
+        if HAS_SD:
+            sd.stop()
+
+
+def main():
+    ap = argparse.ArgumentParser()
+    ap.add_argument("--config", default="config.toml")
+    ap.add_argument("--a", default=None)
+    ap.add_argument("--b", default=None)
+    ap.add_argument("--device", default=None, choices=["auto","cpu","cuda"])
+    ap.add_argument("--method", default=None, choices=["phat","standard"])
+    args = ap.parse_args()
+
+    cfg = load_config(args.config)
+    cfg_a, cfg_b, sr, _, _ = find_wavs_from_config(cfg)
+    a_path = args.a or cfg_a
+    b_path = args.b or cfg_b
+    method = args.method or cfg.get("sync", {}).get("method", "phat")
+    device = args.device or cfg.get("sync", {}).get("use_gpu", "auto")
+    # map toml "use_gpu" to device
+    if device == "auto":
+        device = "auto"
+    elif device == "cpu":
+        device = "cpu"
+    elif device in ("cuda", "gpu"):
+        device = "cuda"
+
+    if not a_path or not b_path:
+        print(f"ERROR: no input wavs. Set file_a/file_b in {args.config} or --a/--b", file=sys.stderr)
+        sys.exit(1)
+    if not os.path.exists(a_path):
+        print(f"ERROR: A not found {a_path}", file=sys.stderr); sys.exit(1)
+    if not os.path.exists(b_path):
+        print(f"ERROR: B not found {b_path}", file=sys.stderr); sys.exit(1)
+
+    app = QtWidgets.QApplication(sys.argv)
+    pg.setConfigOptions(antialias=True, background="#121212", foreground="#eee")
+    w = SyncWindow(a_path, b_path, sr=sr, method=method, device=device)
+    w.show()
+    sys.exit(app.exec())
+
+
+if __name__ == "__main__":
+    main()