ffreplace

#!/bin/bash

# Default subtitle language
SUBTITLE_LANG="deu"

# Parse command-line arguments
while [[ "$#" -gt 0 ]]; do
		case $1 in
				--lang) SUBTITLE_LANG="$2"; shift; shift ;;
				*) FILENAME="$1" ;;
		esac
		shift
done

# Check if a filename is provided
if [ -z "$FILENAME" ]; then
		echo "Usage: replace_subtitles <filename> [--lang language_code]"
		echo "Example: replace_subtitles video --lang deu"
		exit 1
fi

# Define input and output files
INPUT_MP4="${FILENAME}.mp4"
BACKUP_MP4="${FILENAME}.backup.mp4"
INPUT_SRT="${FILENAME}.srt"
OUTPUT_MP4="${FILENAME}.mp4"

# Check if input MP4 file exists
if [ ! -f "$INPUT_MP4" ]; then
		echo "Error: $INPUT_MP4 not found!"
		exit 1
fi

# Check if input SRT file exists
if [ ! -f "$INPUT_SRT" ]; then
		echo "Error: $INPUT_SRT not found!"
		exit 1
fi

# Create a backup of the original MP4 file
cp "$INPUT_MP4" "$BACKUP_MP4"

# Run ffmpeg to replace subtitles using the backup as input
ffmpeg -i "$BACKUP_MP4" -i "$INPUT_SRT" \
			 -c:v copy -c:a copy \
			 -c:s mov_text \
			 -map 0:v -map 0:a -map 1:s \
			 -metadata:s:s:0 language="$SUBTITLE_LANG" \
			 "$OUTPUT_MP4"

# Check if ffmpeg succeeded
if [ $? -eq 0 ]; then
		echo "Subtitles replaced successfully: $OUTPUT_MP4 created."
		echo "Backup of the original file: $BACKUP_MP4"
else
		echo "Subtitle replacement failed!"
		exit 1
fi