copy tags using a python script in reduce-bitrate

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"
-        log_success "Converted: ${file} (${current_bitrate} kbps ➜ ${TARGET_BITRATE}) ✅"
-        ((converted_count++))
+
+        # Restore all metadata from backup file
+        if restore_metadata "$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}"
@@ -113,7 +134,12 @@ while getopts ":nd:ch" opt; do
 done
 
 if ! command -v ffprobe >/dev/null 2>&1 || ! command -v ffmpeg >/dev/null 2>&1; then
-    log_error "ffprobe/ffmpeg not found. Please install ffmpeg." 
+    log_error "ffprobe/ffmpeg not found. Please install ffmpeg."
+    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