A script I use to quickly download YouTube videos into my music folder as .ogg files.

ytdl-ogg.sh

#!/usr/bin/env bash
# ytdl-ogg - quickly download a youtube video from a URL and save to an ogg,
#            with an optional custom filename.
#
# USAGE:
#   ytdl-ogg <URL> <output filename>
#   
#   If a custom filename is given, it will save to that name under OUTDIR.
#   Otherwise, it will save to youtube-dl's default format under OUTDIR.
#
# TODO:
#   - Make this code not look like garbage

# The directory to output files by default, later sorting, as an example.
OUTDIR="$HOME/Music/auto"
UNCDIR="$OUTDIR/unconverted"

if ! [ -d $UNCDIR ]; then mkdir -p $UNCDIR; fi

ytdl_output="$UNCDIR/%(title)s-%(id)s.%(ext)s"

# Download the video's audio.
youtube-dl \
  "$1" \
  -f bestaudio \
  --no-playlist \
  -o "$ytdl_output"

# Use the same parameters but only get the filename.
filename=$(youtube-dl \
  "$1" \
  -f bestaudio \
  -o "$ytdl_output" \
  --get-filename
)

if [ "${filename#*.}" = "webm" ]; then
  # If the container is .webm, that means that the format is opus. For some
  # reason, ffprobe doesn't detect stream bitrate from an opus stream, but
  # can still get it from the format.
  
  # Take audio from downloaded file and save it to a .opus file.
  ffmpeg \
    -v error \
    -i "$filename" \
    -c:a copy \
    "${filename%%.*}.opus"
  
  # Strip the extension from the filename and add ".opus" to it.
  filename="${filename%%.*}.opus"

  # Find bitrate from the "format" section.
  bitrate=$(ffprobe \
    -v error \
    -select_streams a:0 \
    -show_entries format=bit_rate \
    -of compact=p=0:nk=1 \
    "$filename"
  )
else
  # If it isn't .webm, then it's .m4a with a DASH stream. ffprobe can determine
  # the bitrate from the stream, so we tell it to do so here.
  bitrate=$(ffprobe \
    -v error \
    -select_streams a:0 \
    -show_entries stream=bit_rate \
    -of compact=p=0:nk=1 \
    "$filename"
  )
fi

# Determine sample rate from stream section.
samplerate=$(ffprobe \
  -v error \
  -select_streams a:0 \
  -show_entries stream=sample_rate \
  -of compact=p=0:nk=1 \
  "$filename"
)

echo "Bitrate: $bitrate"
echo "Sample Rate: $samplerate"

if [ "$2" ]; then
  # If an output filename is provided, use that.

  if [ "$(basename "$2")" = "$2" ]; then
    # If the basename matches the original string, it's a filename, not a path.
    # Save the file to the name under OUTDIR.
    output_filename="$OUTDIR/$2"
  else
    # If the basename doesn't match the original string, it's under a path.
    # Save the file to that full custom path instead.
    output_filename="$2"
  fi
else
  # Otherwise, save to youtube-dl's format under OUTDIR.
  file_basename=$(basename "$filename")
  file_basename_noextension=${filename_basename%%.*}
  output_filename="$OUTDIR/$file_basename_noextension.ogg"
fi

echo "Saving to: $output_filename"

# Finally, convert the file to .ogg with minimal loss.
ffmpeg \
  -v error \
  -i "$filename" \
  -c:a libvorbis \
  -ab $bitrate \
  -ar $samplerate \
  "$output_filename";

echo "Done."