Merge Audio and Video File

merge_audio_video.sh

#!/usr/bin/env bash
# merge_audio_video.sh — Mux video and MP3/M4A into MP4 with AAC audio

set -euo pipefail

if [ $# -ne 3 ]; then
  echo "Usage: $0 <video.mp4> <audio.(mp3|m4a)> <output.mp4>" >&2
  exit 1
fi

video="$1"
audio="$2"
output="$3"

ffmpeg -i "$video" -i "$audio" \
  -c:v copy -c:a aac -b:a 256k \
  -map 0:v:0 -map 1:a:0 \
  -shortest \
  "$output"