yt-dlp playlist concurrent downloader

yt-dlp-all

#!/usr/bin/env zsh

playlistUrl="$1";
numParallelDownloads="${2:-5}";
numParallelFragments="${3:-5}";

[[ -z "$playlistUrl" ]] && echo 'i need a url to a yt playlist please.' >&2 && exit 1;
[[ "$numParallelDownloads" =~ '^[^0-9]+$' ]] && echo "expected parameter 2 to be the number of parallel downloads, got '$numParallelDownloads'." >&2 && exit 1;
[[ "$numParallelFragments" =~ '^[^0-9]+$' ]] && echo "expected parameter 3 to be the number of parallel fragments, got '$numParallelFragments'." >&2 && exit 1;

echo "Reading playlist, this could take a while depending on the number of items...";
echo "URL: $playlistUrl";
echo "Num Parallel Downloads: $numParallelDownloads";
echo "Num Parallel Fragments: $numParallelFragments";
echo ;

yt-dlp \
  --yes-playlist \
  --skip-download \
  --quiet \
  --print '%(id)s' \
  "$playlistUrl" \
  | xargs \
    -I '{}' \
    -P "$numParallelDownloads" \
    yt-dlp \
      --newline \
      --embed-metadata \
      --write-subs \
      --convert-subs srt \
      --concurrent-fragments "$numParallelFragments" \
      --format 'bv*[ext=mp4]+ba[ext=m4a]/b[ext=mp4] / bv*+ba/b' \
      '{}';