set all undefined audio stream of mp4 movies to english

fixundefinedaudio.sh

#!/bin/bash

function process_file() {
  movie_file="$1"
  echo "Checking $movie_file"
  if ffprobe -v error -show_format -select_streams a:0 -show_streams "$movie_file" | grep "language=und"; then
    echo "Movie audio undefined: updating $movie_fil ( do not CTRL+C )" # remove .bak file if exist
    # Create a backup
    backup_file="${movie_file}.bak"
    echo "Creating backup $backup_file"
    cp "$movie_file" "$backup_file"

    # Change audio language metadata
    echo "Setting language to english backup.."
    ffmpeg -y -i "$backup_file" -map 0 -c copy -metadata:s:a:0 language=eng "$movie_file"

    echo "Audio language changed for $movie_file"
    rm $backup_file
  fi
}

# Find and process MP4 files
#find . -iname "*.mp4" -print0 | xargs -0 -I '{}' sh -c 'process_file "$1"' _ '{}'
echo "Updating all undefined '*YTS*.mp4' audio streams to english"
echo "Starting... (cleanup)"
for i in $(find . -iname "*.bak" ); do
    echo "Removing $i"
    rm $i
done

echo "Looking movies with undefined audio stream..."
for i in $(find . -iname "*.mp4" ); do
    process_file "$i"
done