
The default is 5 and might be a better choice depending on the source quality. The -audio-quality 0 uses the highest encoding quality but can increase your file size unnecessarily. So your command could be: youtube-dl -f bestaudio -extract-audio -audio-format mp3 -audio-quality 0 audio-quality QUALITY Specify ffmpeg/avconv audio quality, insert a value between 0 (better) and 9 (worse) for VBR or a specific bitrate like 128K (default audio-format FORMAT Specify audio format: "best", "aac", "vorbis", "mp3", "m4a", "opus", or "wav" "best" by default



From man youtube-dl: -x, -extract-audio Convert video files to audio-only files (requires ffmpeg or avconv and ffprobe or avprobe)
