My children want to have some of the songs they listen on the radio in their MP3s.
This is a no-brainer. After they find the videos they want in YouTube, I put all the URLs in a file ('bajar.txt') and can get all the MP3 files with the following command.
youtube-dl -a bajar.txt -x --audio-format mp3 -o '%(title)s.%(ext)s'
But the second step is a bit more fun. One of the MP3s is wrong and it plays the songs a bit slower than it should. Instead of buying a new one, I just speed up the MP3 files in the computer before uploading them to the player. This script will just get all the *mp3 files in a directory, speed them up according to the SP factor, and copy them to the directory 'emma_mp3s', ready to upload to my daughter's player (modifying the IFS variable allows having white spaces in the file names)
#!/bin/bash
# mp3speed.sh # Adapted from https://ubuntuforums.org/showthread.php?t=1259851
SAVEIFS=$IFS
IFS=$(echo -en "\n\b")
FILES="*.mp3"
mkdir -p emma_mp3s
for f in $FILES
do
AR=96k
SP=1.08897 # Speed up: ini_length * (1/speedup) = final_length
echo Encoding $f
mplayer -af scaletempo -speed $SP $f -vc null -vo null -ao pcm:fast:waveheader:file=$f.wav
ffmpeg -i $f.wav -acodec libmp3lame -ab $AR emma_mp3s/$f
rm $f.wav
done
IFS=$SAVEIFS
