ffmpeg_video_transcoding

video_transcoding

#!/usr/bin/:/usr/local/bin/

# set -u: only allow referencing of variables if they were previously defined
# set -o pipefail: don't mask pipeline errors
set -uo pipefail

# case-insensitive regex matching
setopt nocasematch

video_input_dir=""
video_output_dir="."
thumbnail_output_dir="."

# The convert_video() function transcodes an input mpg stream into h.264 mp4 video with the following parameters:
#   c:v libx264 => create H.264 video using the encoder x264
#   profile:v main => use main profile (see https://trac.ffmpeg.org/wiki/Encode/H.264#Compatibility for compatibility)
#   r 30 => force frame rate to 30 fps
#   c:a libfdk_aac => Use Fraunhofer FDK AAC codec library (currently the highest-quality AAC encoder available with ffmpeg, see https://trac.ffmpeg.org/wiki/Encode/AAC. Requires ffmpeg to be compiled with --enable-libfdk-aac, see https://trac.ffmpeg.org/wiki/CompilationGuide)
#   ac 2 => downmix to stereo
#   b:a 160k => use constant bit rate of 160kbits
#   ar 44100 => set audio sampling frequency to 44.1khz
#   nostdin => prevent ffmpeg from reading its standard input
function convert_video() {
  mkdir -p logs
  basename="$(basename "$1")"
  basename="$(echo -e "${basename}" | tr -d '[:space:]')" # strip whitespaces
  mp4_filename="${basename%.*}.mp4"
  if ! [[ "$basename" =~ ^[0-9]{4,6}.(mpg|mp4|wmv|mov)$ ]]; then
    echo "$1 invalid filename, skipping..."
    echo "$1" >> logs/invalid_filenames.log
  elif [ -e "$video_output_dir/$mp4_filename" ]; then
    echo "$mp4_filename already exists, skipping..."
  else
    echo "Transcoding $1"
    ffmpeg -i "$1" -c:v libx264 -profile:v main -r 30 -c:a libfdk_aac -ac 2 -b:a 160k -ar 44100 "$video_output_dir/$mp4_filename" &>"$video_output_dir/logs/$mp4_filename.log" -nostdin || log_errors
    ffmpeg -i "$video_output_dir/$mp4_filename" -ss 00:00:10.000 -vframes 1 "$thumbnail_output_dir/$mp4_filename.jpg" -nostdin
  fi
}

# log files that ffmpeg couldn't handle and remove broken output file
function log_errors () {
  echo "$file" >> logs/broken_files.log
  rm "$video_output_dir/$mp4_filename"
}

# find all files in subdirectories (at least 2 levels nested) and transcode them
while IFS= read -r file; do
  convert_video "$file"
done < <(find "$video_input_dir" -mindepth 2 -type f)