waveform

#!/bin/sh

#===============================================================================
# waveform
# create a waveform from an audio or video file and save as a png
#===============================================================================

# dependencies:
# ffmpeg

#===============================================================================
# script usage
#===============================================================================

usage()
{
# if argument passed to function echo it
[ -z "${1}" ] || echo "! ${1}"
# display help
echo "\
# create a waveform from an audio or video file and save as a png

$(basename "$0") -i input.(mp4|mkv|mov|m4v|webm|aac|m4a|wav|mp3) -o output.png
-i output.(mp4|mkv|mov|m4v|aac|m4a|wav|mp3)
-o output.png : optional argument # if option not provided defaults to input-name-waveform-date-time"
exit 2
}


#===============================================================================
# error messages
#===============================================================================

INVALID_OPT_ERR='Invalid option:'
REQ_ARG_ERR='requires an argument'
WRONG_ARGS_ERR='wrong number of arguments passed to script'


#===============================================================================
# check the number of arguments passed to the script
#===============================================================================

[ $# -gt 0 ] || usage "${WRONG_ARGS_ERR}"


#===============================================================================
# getopts check the options passed to the script
#===============================================================================

while getopts ':i:o:h' opt
do
  case ${opt} in
     i) infile="${OPTARG}";;
     o) outfile="${OPTARG}";;
     h) usage;;
     \?) usage "${INVALID_OPT_ERR} ${OPTARG}" 1>&2;;
     :) usage "${INVALID_OPT_ERR} ${OPTARG} ${REQ_ARG_ERR}" 1>&2;;
  esac
done
shift $((OPTIND-1))


#===============================================================================
# variables
#===============================================================================

# variables
infile_nopath="${infile##*/}"
infile_name="${infile_nopath%.*}"

# defaults for variables if not defined
outfile_default="${infile_name}-waveform-$(date +"%Y-%m-%d-%H-%M-%S").png"


#===============================================================================
# functions
#===============================================================================

# waveform function
wform () {
    ffmpeg \
    -hide_banner \
    -stats -v panic \
    -i "${infile}" \
    -filter_complex "aformat=channel_layouts=mono,showwavespic=s=1000x200" \
    -frames:v 1 \
     -f apng \
    "${outfile:=${outfile_default}}"
}

# run the wform function
wform "${infile}"