A

.gitignore

@@ -0,0 +1,11 @@
+# FFmpeg (vendored Windows build)
+ffmpeg-*/
+
+# Conversion outputs
+out/
+
+# Local/dev artifacts
+.venv/
+__pycache__/
+*.py[cod]
+.idea/

convert.py

@@ -4,19 +4,22 @@ Outputs are written flat into E:\\Music\\工具\\TypeChange\\out; if two source
 or existing outputs share the same name, the last one wins and a summary of
 overwrites is printed at the end.
 
-If `mutagen` is installed, FLAC tags (Vorbis comments) and cover art are written
-to the output M4A using standard MP4/iTunes atoms (including `covr`).
+Notes:
+- If the source is already `.m4a`, it is copied as-is by default (no re-encode).
+- If `mutagen` is installed, FLAC tags (Vorbis comments) and cover art are written
+  to the output M4A using standard MP4/iTunes atoms (including `covr`).
 """
 
 import os
 import argparse
 import subprocess
+import shutil
 import sys
 from pathlib import Path
 from concurrent.futures import ThreadPoolExecutor, as_completed
 
 # Source and destination roots
-SOURCE_ROOT = Path(r"E:\Music\完成\单曲")
+SOURCE_ROOT = Path(r"E:\Music")
 SKIP_ROOT = SOURCE_ROOT / "工具"
 OUT_ROOT = Path(r"E:\Music\工具\TypeChange\out")
 
@@ -294,7 +297,7 @@ def sync_tags_from_flac(src: Path, dst: Path) -> bool:
     return True
 
 
-def convert_file(src: Path, dst: Path, *, tags_only: bool) -> bool:
+def convert_file(src: Path, dst: Path, *, tags_only: bool, copy_m4a: bool) -> bool:
     """Run ffmpeg to transcode a single file to AAC. Returns True on success."""
     dst.parent.mkdir(parents=True, exist_ok=True)
 
@@ -313,15 +316,35 @@ def convert_file(src: Path, dst: Path, *, tags_only: bool) -> bool:
             sys.stderr.write(f"[WARN] Tag sync failed for {dst}: {exc}\n")
             return False
 
+    if copy_m4a and src.suffix.lower() == ".m4a":
+        try:
+            shutil.copy2(src, dst)
+            return True
+        except OSError as exc:
+            sys.stderr.write(f"[FAIL] copy {src} -> {dst} ({exc})\n")
+            return False
+
     cmd = [FFMPEG_BIN, "-y"]  # overwrite if needed
     cmd += ["-i", str(src)]
+    external_cover = find_external_cover_image(src)
+    if external_cover:
+        cmd += ["-i", str(external_cover)]
+    cmd += ["-map", "0:a:0"]  # first audio stream
+    if external_cover:
+        cmd += ["-map", "1:v:0"]  # external cover image
+        cmd += ["-disposition:v:0", "attached_pic"]
+    else:
+        cmd += ["-map", "0:v:0?"]  # embedded cover art if present
+    cmd += ["-map", "0:s?"]  # keep subtitle streams (some files store lyrics as subtitles)
     cmd += [
-        "-map",
-        "0:a",  # audio only; cover art + full tags are applied in a separate step
         "-map_metadata",
         "0",  # copy tags
         "-map_chapters",
         "0",
+        "-c:v",
+        "copy",
+        "-c:s",
+        "mov_text",
         "-c:a",
         "aac",  # re-encode audio
         "-b:a",
@@ -351,6 +374,11 @@ def parse_args():
         action="store_true",
         help="Skip transcoding; only sync FLAC tags/cover to existing outputs in OUT_ROOT.",
     )
+    parser.add_argument(
+        "--no-copy-m4a",
+        action="store_true",
+        help="Do not copy .m4a sources; re-encode them to AAC like other formats (default: copy).",
+    )
     return parser.parse_args()
 
 
@@ -398,12 +426,14 @@ def main():
         for p in preexisting_outputs:
             print(f"  {p}")
 
-    max_workers = max(1, os.cpu_count() or 4)
+    max_workers = max(1, os.cpu_count() / 2 or 4)
     successes = 0
 
     print(f"Using ffmpeg at: {FFMPEG_BIN}")
     if not HAS_MUTAGEN:
         print("Note: Install 'mutagen' to fully preserve FLAC tags/cover art (pip install mutagen).")
+    if not args.no_copy_m4a and not args.tags_only:
+        print("Note: .m4a sources are copied as-is (use --no-copy-m4a to force re-encode).")
     if args.tags_only:
         print("Mode: tags-only (no transcoding).")
     if args.tags_only:
@@ -415,7 +445,13 @@ def main():
     with ThreadPoolExecutor(max_workers=max_workers) as executor:
         future_map = {}
         for src, dst in tasks:
-            future = executor.submit(convert_file, src, dst, tags_only=args.tags_only)
+            future = executor.submit(
+                convert_file,
+                src,
+                dst,
+                tags_only=args.tags_only,
+                copy_m4a=not args.no_copy_m4a,
+            )
             future_map[future] = (src, dst)
 
         for future in as_completed(future_map):