copy tags using a python script in reduce-bitrate

copy_id3_tags.py

@@ -0,0 +1,46 @@
+#!/usr/bin/env python3
+"""
+Copy all ID3 tags from source file to target file, preserving multi-value fields.
+Requires: python-mutagen
+"""
+
+import sys
+from mutagen.id3 import ID3, ID3NoHeaderError
+
+def copy_id3_tags(source_path, target_path):
+    """Copy all ID3 tags from source to target file."""
+    try:
+        # Load source tags
+        source_tags = ID3(source_path)
+
+        # Load or create target tags
+        try:
+            target_tags = ID3(target_path)
+        except ID3NoHeaderError:
+            target_tags = ID3()
+
+        # Clear all existing tags in target
+        target_tags.clear()
+
+        # Copy all frames from source to target
+        for key, value in source_tags.items():
+            target_tags[key] = value
+
+        # Save to target file
+        target_tags.save(target_path, v2_version=3)
+
+        return 0
+
+    except Exception as e:
+        print(f"Error copying tags: {e}", file=sys.stderr)
+        return 1
+
+if __name__ == "__main__":
+    if len(sys.argv) != 3:
+        print("Usage: copy_id3_tags.py <source_file> <target_file>", file=sys.stderr)
+        sys.exit(1)
+
+    source = sys.argv[1]
+    target = sys.argv[2]
+
+    sys.exit(copy_id3_tags(source, target))

reduce_bitrate.sh

@@ -52,6 +52,17 @@ get_bitrate_kbps() {
     return 1
 }
 
+restore_metadata() {
+    local source_file="$1"
+    local target_file="$2"
+    local script_dir="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
+
+    # Use Python script with mutagen to properly copy all ID3 tags including multi-value fields
+    "$script_dir/copy_id3_tags.py" "$source_file" "$target_file" 2>/dev/null
+
+    return $?
+}
+
 process_file() {
     local file="$1"
     local current_bitrate
@@ -85,8 +96,18 @@ process_file() {
     temp_file="${file%.mp3}_temp_$$.mp3"
     if ffmpeg -nostdin -y -i "$file" -b:a "${TARGET_BITRATE}" -id3v2_version 3 "$temp_file" > /dev/null 2>&1; then
         mv "$temp_file" "$file"
+
+        # Restore all metadata from backup file
+        if restore_metadata "$backup_file" "$file"; then
             log_success "Converted: ${file} (${current_bitrate} kbps ➜ ${TARGET_BITRATE}) ✅"
             ((converted_count++))
+        else
+            log_error "Metadata restoration failed: ${file}"
+            # Revert to backup since metadata restoration failed
+            cp "$backup_file" "$file"
+            log_warn "Reverted to backup (conversion skipped due to metadata error)"
+            ((error_count++))
+        fi
     else
         rm -f "$temp_file"
         log_error "ffmpeg failed: ${file}"
@@ -117,6 +138,11 @@ if ! command -v ffprobe >/dev/null 2>&1 || ! command -v ffmpeg >/dev/null 2>&1;
     exit 1
 fi
 
+if ! python3 -c "import mutagen" 2>/dev/null; then
+    log_error "Python mutagen library not found. Please install python-mutagen (Arch) or python3-mutagen (Debian/Ubuntu)."
+    exit 1
+fi
+
 if [ ! -d "$ROOT_DIR" ]; then
     log_error "Directory not found: ${ROOT_DIR}"
     exit 1