commit 9af23d0c643b006c9efae315efa4043df4de8723
Author: Mathieu Broillet <mathieu@broillet.ch>
Date:   Fri Jan 23 12:06:39 2026 +0100

    feat: initial commit

diff --git a/main.py b/main.py
new file mode 100644
index 0000000..939989b
--- /dev/null
+++ b/main.py
@@ -0,0 +1,175 @@
+import argparse
+import json
+import logging
+import shutil
+import subprocess
+import sys
+from pathlib import Path
+
+EXTENSIONS = {".mkv", ".mp4"}
+
+# ----------------------------
+# CLI
+# ----------------------------
+parser = argparse.ArgumentParser(
+    description="Convert AAC 5.1 / 7.1 audio to E-AC-3 without touching other streams"
+)
+parser.add_argument("path", help="Directory containing media files")
+parser.add_argument("--ffmpeg", default="ffmpeg", help="Path to ffmpeg binary")
+parser.add_argument("--overwrite", action="store_true", help="Overwrite original files")
+parser.add_argument("--dry-run", action="store_true", help="Show what would be done without converting")
+args = parser.parse_args()
+
+# ----------------------------
+# Logging
+# ----------------------------
+logging.basicConfig(
+    level=logging.INFO,
+    format="%(asctime)s | %(levelname)-7s | %(message)s",
+    datefmt="%H:%M:%S"
+)
+log = logging.getLogger("aac2eac3")
+
+
+# ----------------------------
+# Helpers
+# ----------------------------
+
+def ffprobe_path():
+    return args.ffmpeg.replace("ffmpeg", "ffprobe")
+
+
+def probe_streams(file: Path):
+    """Get info about all streams in a file."""
+    cmd = [
+        ffprobe_path(),
+        "-v", "error",
+        "-show_entries", "stream=index,codec_type,codec_name,channels:stream_tags=language,title",
+        "-of", "json",
+        str(file)
+    ]
+    result = subprocess.run(cmd, capture_output=True, text=True)
+    data = json.loads(result.stdout)
+    return data.get("streams", [])
+
+
+def build_output_name(file: Path):
+    if args.overwrite:
+        return file.with_suffix(".tmp" + file.suffix)
+    return file.with_name(f"{file.stem}.eac{file.suffix}")
+
+
+# ----------------------------
+# Conversion
+# ----------------------------
+
+def convert(file: Path):
+    streams = probe_streams(file)
+    if not streams:
+        log.warning("No streams found: %s", file.name)
+        return
+
+    # Build FFmpeg codec maps
+    codec_map = {}
+    target_bitrates = {}
+    has_aac_multichannel = False
+
+    for s in streams:
+        if s["codec_type"] == "audio":
+            # Only re-encode AAC 5.1 or 7.1
+            if s["codec_name"] == "aac" and s.get("channels") in (6, 8):
+                codec_map[s["index"]] = "eac3"
+                target_bitrates[s["index"]] = "640k" if s["channels"] == 6 else "1024k"
+                has_aac_multichannel = True
+            else:
+                codec_map[s["index"]] = "copy"
+        elif s["codec_type"] == "video":
+            codec_map[s["index"]] = "copy"
+        elif s["codec_type"] == "subtitle":
+            codec_map[s["index"]] = "copy"
+
+    if not has_aac_multichannel:
+        log.info("Skipping %s (no AAC 5.1/7.1 tracks)", file.name)
+        return
+
+    output = build_output_name(file)
+
+    if args.dry_run:
+        log.info("[DRY RUN] Would convert %s → %s", file.name, output.name)
+        for s in streams:
+            if s["codec_type"] == "audio" and s["index"] in codec_map:
+                action = codec_map[s["index"]]
+                if action == "eac3":
+                    log.info("  [DRY RUN] Stream %d: %s %dch → E-AC-3 @ %s",
+                             s["index"], s["codec_name"], s.get("channels", 0),
+                             target_bitrates[s["index"]])
+                else:
+                    log.info("  [DRY RUN] Stream %d: %s (copy)",
+                             s["index"], s["codec_name"])
+        return
+
+    cmd = [args.ffmpeg, "-y", "-hide_banner", "-loglevel", "info", "-stats", "-i", str(file)]
+
+    # Map all streams
+    cmd += ["-map", "0"]
+
+    # Set codecs
+    for idx, c in codec_map.items():
+        cmd += [f"-c:{idx}", c]
+        if c == "eac3":
+            cmd += [f"-b:a:{idx}", target_bitrates[idx]]
+
+    # Preserve metadata
+    cmd += ["-map_metadata", "0", str(output)]
+
+    log.info("Converting %s → %s", file.name, output.name)
+
+    process = subprocess.Popen(cmd, stdout=sys.stdout, stderr=sys.stderr)
+    process.wait()
+
+    if process.returncode != 0:
+        log.error("FFmpeg failed: %s", file.name)
+        if output.exists():
+            output.unlink(missing_ok=True)
+        return
+
+    if args.overwrite:
+        backup = file.with_suffix(file.suffix + ".bak")
+        log.info("Replacing original file")
+        shutil.move(file, backup)
+        shutil.move(output, file)
+        backup.unlink(missing_ok=True)
+
+    log.info("Completed: %s", file.name)
+
+
+# ----------------------------
+# Main
+# ----------------------------
+
+def main():
+    root = Path(args.path).resolve()
+    if not root.is_dir():
+        raise SystemExit(f"Invalid directory: {root}")
+
+    files = sorted(f for f in root.rglob("*") if f.suffix.lower() in EXTENSIONS)
+    if not files:
+        log.warning("No media files found")
+        return
+
+    log.info("Found %d files", len(files))
+    if args.dry_run:
+        log.info("=== DRY RUN MODE - No files will be modified ===")
+
+    for file in files:
+        try:
+            convert(file)
+        except KeyboardInterrupt:
+            log.warning("Interrupted by user")
+            sys.exit(130)
+        except Exception:
+            log.exception("Unexpected error while processing %s", file.name)
+
+
+if __name__ == "__main__":
+    main()
\ No newline at end of file