commit 8ae6274806a6cf1ccc80c62e4ae43b1bf1987184
Author: nnduc <nnduc@home>
Date:   Sat Jul 12 19:27:13 2025 +0700

    add flac downsampling

diff --git a/ffmpeg-flac-downsampling.sh b/ffmpeg-flac-downsampling.sh
new file mode 100644
index 0000000..b2d63fa
--- /dev/null
+++ b/ffmpeg-flac-downsampling.sh
@@ -0,0 +1,268 @@
+#!/bin/bash
+
+# Media Library FLAC Downsampling Script
+# Processes multiple albums in a media library, downsampling all FLAC files to 44.1 kHz
+
+# Check if ffmpeg is installed
+if ! command -v ffmpeg &> /dev/null; then
+    echo "Error: ffmpeg is not installed or not in PATH"
+    exit 1
+fi
+
+# Function to display usage
+show_usage() {
+    echo "Usage: $0 [OPTIONS] <media_library_path>"
+    echo ""
+    echo "Options:"
+    echo "  -o, --output DIR     Output directory (default: creates _44k suffix)"
+    echo "  -r, --replace        Replace original files (use with caution)"
+    echo "  -p, --preserve       Preserve original files alongside new ones"
+    echo "  -t, --test           Test mode - show what would be processed"
+    echo "  -h, --help           Show this help message"
+    echo ""
+    echo "Examples:"
+    echo "  $0 /path/to/music/library"
+    echo "  $0 -o /path/to/output /path/to/music/library"
+    echo "  $0 --test /path/to/music/library"
+    echo "  $0 --replace /path/to/music/library"
+}
+
+# Default options
+OUTPUT_DIR=""
+REPLACE_MODE=false
+PRESERVE_MODE=false
+TEST_MODE=false
+PROCESSED_COUNT=0
+SKIPPED_COUNT=0
+ERROR_COUNT=0
+
+# Parse command line arguments
+while [[ $# -gt 0 ]]; do
+    case $1 in
+        -o|--output)
+            OUTPUT_DIR="$2"
+            shift 2
+            ;;
+        -r|--replace)
+            REPLACE_MODE=true
+            shift
+            ;;
+        -p|--preserve)
+            PRESERVE_MODE=true
+            shift
+            ;;
+        -t|--test)
+            TEST_MODE=true
+            shift
+            ;;
+        -h|--help)
+            show_usage
+            exit 0
+            ;;
+        -*)
+            echo "Unknown option: $1"
+            show_usage
+            exit 1
+            ;;
+        *)
+            MEDIA_LIBRARY="$1"
+            shift
+            ;;
+    esac
+done
+
+# Check if media library path is provided
+if [ -z "$MEDIA_LIBRARY" ]; then
+    echo "Error: Media library path is required"
+    show_usage
+    exit 1
+fi
+
+# Check if media library exists
+if [ ! -d "$MEDIA_LIBRARY" ]; then
+    echo "Error: Media library directory '$MEDIA_LIBRARY' not found"
+    exit 1
+fi
+
+# Set output directory if not specified
+if [ -z "$OUTPUT_DIR" ] && [ "$REPLACE_MODE" = false ]; then
+    OUTPUT_DIR="${MEDIA_LIBRARY}_44k"
+fi
+
+# Function to check if file needs downsampling
+needs_downsampling() {
+    local file="$1"
+    
+    # Check if file is readable
+    if [ ! -r "$file" ]; then
+        echo "    WARNING: File not readable: $file"
+        return 1
+    fi
+    
+    local sample_rate=$(ffprobe -v quiet -select_streams a:0 -show_entries stream=sample_rate -of csv=p=0 "$file" 2>/dev/null)
+    
+    if [ -z "$sample_rate" ]; then
+        echo "    WARNING: Could not determine sample rate for: $(basename "$file")"
+        return 1  # Skip files we can't analyze
+    elif [ "$sample_rate" = "44100" ]; then
+        return 1  # No downsampling needed
+    else
+        echo "    Current sample rate: ${sample_rate} Hz"
+        return 0  # Needs downsampling
+    fi
+}
+
+# Function to process a single FLAC file
+process_flac_file() {
+    local input_file="$1"
+    local relative_path="$2"
+    local output_file=""
+    
+    # Determine output file path
+    if [ "$REPLACE_MODE" = true ]; then
+        output_file="$input_file"
+    elif [ "$PRESERVE_MODE" = true ]; then
+        local dir=$(dirname "$input_file")
+        local filename=$(basename "$input_file" .flac)
+        output_file="$dir/${filename}_44k.flac"
+    else
+        output_file="$OUTPUT_DIR/$relative_path"
+    fi
+    
+    # Check if downsampling is needed
+    if ! needs_downsampling "$input_file"; then
+        echo "  SKIP: $relative_path (already 44.1 kHz)"
+        ((SKIPPED_COUNT++))
+        return
+    fi
+    
+    if [ "$TEST_MODE" = true ]; then
+        echo "  WOULD PROCESS: $relative_path → $(basename "$output_file")"
+        return
+    fi
+    
+    # Create output directory if needed
+    local output_dir=$(dirname "$output_file")
+    if [ ! -d "$output_dir" ]; then
+        echo "    Creating directory: $output_dir"
+        if ! mkdir -p "$output_dir"; then
+            echo "  ✗ ERROR: Cannot create output directory: $output_dir"
+            ((ERROR_COUNT++))
+            return
+        fi
+    fi
+    
+    # Verify input file exists and is readable
+    if [ ! -f "$input_file" ]; then
+        echo "  ✗ ERROR: Input file not found: $input_file"
+        ((ERROR_COUNT++))
+        return
+    fi
+    
+    if [ ! -r "$input_file" ]; then
+        echo "  ✗ ERROR: Input file not readable: $input_file"
+        ((ERROR_COUNT++))
+        return
+    fi
+    
+    # Create temporary file for safe processing (use .flac extension)
+    local temp_file="${output_file}.tmp.flac"
+    
+    echo "  PROCESSING: $relative_path"
+    
+    # Downsample the file
+    echo "    Command: ffmpeg -i \"$input_file\" -ar 44100 -c:a flac -compression_level 8 -y \"$temp_file\""
+    
+    if ffmpeg -i "$input_file" -ar 44100 -c:a flac -compression_level 8 -y "$temp_file" 2>"${temp_file}.log"; then
+        # Move temp file to final location
+        mv "$temp_file" "$output_file"
+        echo "  ✓ DONE: $(basename "$output_file")"
+        rm -f "${temp_file}.log"
+        ((PROCESSED_COUNT++))
+    else
+        echo "  ✗ ERROR: Failed to process $relative_path"
+        echo "    Error log saved to: ${temp_file}.log"
+        if [ -f "${temp_file}.log" ]; then
+            echo "    Last few lines of error:"
+            tail -n 5 "${temp_file}.log" | sed 's/^/    /'
+        fi
+        rm -f "$temp_file"
+        ((ERROR_COUNT++))
+    fi
+}
+
+# Function to process an album directory
+process_album() {
+    local album_dir="$1"
+    local album_name=$(basename "$album_dir")
+    
+    echo "Processing album: $album_name"
+    
+    # Find all FLAC files in the album directory
+    local flac_files=()
+    while IFS= read -r -d '' file; do
+        flac_files+=("$file")
+    done < <(find "$album_dir" -name "*.flac" -type f -print0)
+    
+    if [ ${#flac_files[@]} -eq 0 ]; then
+        echo "  No FLAC files found in $album_name"
+        return
+    fi
+    
+    # Process each FLAC file
+    for flac_file in "${flac_files[@]}"; do
+        local relative_path="${flac_file#$MEDIA_LIBRARY/}"
+        process_flac_file "$flac_file" "$relative_path"
+    done
+    
+    echo ""
+}
+
+# Main processing
+echo "Media Library FLAC Downsampler"
+echo "==============================="
+echo "Input:  $MEDIA_LIBRARY"
+
+if [ "$TEST_MODE" = true ]; then
+    echo "Mode:   TEST MODE (no files will be modified)"
+elif [ "$REPLACE_MODE" = true ]; then
+    echo "Mode:   REPLACE (original files will be overwritten)"
+elif [ "$PRESERVE_MODE" = true ]; then
+    echo "Mode:   PRESERVE (44k files created alongside originals)"
+else
+    echo "Output: $OUTPUT_DIR"
+fi
+
+echo ""
+
+# Find all directories that contain FLAC files (potential albums)
+album_dirs=()
+while IFS= read -r -d '' dir; do
+    if find "$dir" -maxdepth 1 -name "*.flac" -type f | grep -q .; then
+        album_dirs+=("$dir")
+    fi
+done < <(find "$MEDIA_LIBRARY" -type d -print0)
+
+if [ ${#album_dirs[@]} -eq 0 ]; then
+    echo "No albums with FLAC files found in $MEDIA_LIBRARY"
+    exit 0
+fi
+
+echo "Found ${#album_dirs[@]} album(s) with FLAC files"
+echo ""
+
+# Process each album
+for album_dir in "${album_dirs[@]}"; do
+    process_album "$album_dir"
+done
+
+# Summary
+echo "Processing Summary:"
+echo "=================="
+echo "Processed: $PROCESSED_COUNT files"
+echo "Skipped:   $SKIPPED_COUNT files (already 44.1 kHz)"
+echo "Errors:    $ERROR_COUNT files"
+
+if [ "$ERROR_COUNT" -gt 0 ]; then
+    exit 1
+fi