Converts a directory of video files to audio files with ffmpeg

video2audio.sh

#!/bin/bash
# Convert a directory of videos to audio files
# 
# ## Requirements
# bc, ffmpeg
#
# ## Usage
# Call from a directory containing videos:
#
#     video2audio 10 20 1 mp3 
#
# Or, to accept all default values:
#
#     video2audio
#
# The first argument is the amount of time (in seconds) to trim from the 
# beginning of the audio file (default 0 seconds).
#
# The second argument is the amount of time (in seconds) to trim from the 
# end of the audio file (default 0 seconds).
#
# The third argument is the audio track you would like to convert. By
# default the first track (0) will be used.
#
# The fourth argument is the format you would like the audio file to use
# (default mp3). See ffmpeg docs for a list of supported audio formats.
# The fourth argument is the name you would like to set for the artist and
# album title. If this is not set the name of the current directory will be
# used.

TRIM_START=${1:-0}
TRIM_END=${2:-0}
AUDIO_TRACK=${3:-0}
FORMAT=${4:-mp3}
OUTPUT_PATH="audio/"
ALBUM=${PWD##*/}
ARTIST=$ALBUM

mkdir -p "$OUTPUT_PATH"

declare -a TYPES=(
    "mkv" "mp4" "avi" "wmv"
)

for TYPE in ${TYPES[@]}; do

    for FILE in *.$TYPE; do
        if [ -e "$FILE" ]; then
            LENGTH=$(ffprobe -v 0 -show_entries FORMAT=duration -of compact=p=0:nk=1 "$FILE")
            TRIM_END="$LENGTH - $TRIM_END" | bc
            ffmpeg -y -ss $TRIM_START -t $TRIM_END -i "$FILE" -c:a $FORMAT -map 0:a:$AUDIO_TRACK -metadata title="${FILE%.*}" -metadata artist="$ARTIST" -metadata album="$ALBUM" "$OUTPUT_PATH${FILE%.*}.$FORMAT"
        fi
    done

done

Updated to fix "Invalid stream specifier: audio." issue. "-c:audio" is no longer valid in ffmpeg.

• Added argument for selecting which audio track to extract
• Audio is now output to an "audio" directory rather than dumped into the same folder