synology_dlna_mp4_fix.sh

#!/bin/bash

# Synology DLNA server does not recognize mp4 audio files 
# but does recognize them if ther are .M4A. 
# https://www.synology.com/en-global/dsm/software_spec/audio_station

find "${HOME}/Music/tmp" -name "*.mp4" | while read filename
do
    name=$(echo "${filename}" | sed -e "s/.mp4$//g")
    echo "${name}"
    mv "${filename}" "${name}.M4A"
done