app/core/ffmpeg_utils.py

"""
Thin wrappers around ffmpeg/ffprobe subprocess calls.
"""
import json
import subprocess


def probe_duration(path: str) -> float:
    """Returns media duration in seconds via ffprobe."""
    out = subprocess.run(
        ["ffprobe", "-v", "error", "-show_entries", "format=duration",
         "-of", "json", path],
        capture_output=True, text=True, check=True,
    )
    data = json.loads(out.stdout)
    return float(data["format"]["duration"])


def run_ffmpeg(args: list[str], log_path: str | None = None):
    """Runs an ffmpeg command, raising with stderr captured on failure."""
    cmd = ["ffmpeg", "-y"] + args
    result = subprocess.run(cmd, capture_output=True, text=True)
    if log_path:
        with open(log_path, "a") as f:
            f.write(" ".join(cmd) + "\n")
            f.write(result.stderr + "\n")
    if result.returncode != 0:
        raise RuntimeError(f"ffmpeg failed ({result.returncode}): {result.stderr[-2000:]}")
    return result