Download podcasts and name with release order, assuming the feed is delivered in release order.

encode.sh

#!/bin/bash

threads=4

if [ -z "$1" ]; then
  echo "Usage:"
  echo "    encode.sh <output_path>"
  exit 1
fi

dir=$1

mkdir -p $dir

encode() {
  outname=$(echo $1 | sed 's/.mp3//gI')
  outpath="${dir}${outname}.mp3"
  echo "encode ${1} to ${outpath}"
  ffmpeg -v 0 -i "$1" -y -f mp2 -ar 44100 -ab 64000 -ac 1 -acodec mp3 "$outpath"
}
export -f encode
export dir

files=(*.mp3)

for file in "${files[@]}"; do
    echo $file
done | xargs -n 1 -P $threads -I {} bash -c 'encode "$@"' _ {}

feed_download.sh

#!/bin/bash

threads=4
tmp=~/.cache/feed_download

feed="${tmp}/feed.xml"

if command -v python3 &>/dev/null; then
  python=python3
else
  echo "Python 3 is required"
  exit 1
fi

if [ -z "$1" ]; then
  echo "Usage:"
  echo "    feed_download.sh <feed_url>"
  exit 1
fi

download() {
  IFS=';' read -ra ADDR <<< "$1"
  index=${ADDR[0]}
  url=${ADDR[1]}

  filename=$(python3 -c "from urllib.parse import urlparse; print(urlparse('${url}').path.split('/')[-1])")

  output="${index}-${filename}"

  echo "Downloading ${output}"

  curl -Ls -o "${output}" "${url}"
  return 0;
}
export -f download

mkdir -p $tmp
curl -Ls $1 > $feed

array=($(python3 -c "import xml.etree.ElementTree; items = xml.etree.ElementTree.parse('${feed}').find('channel').iter(tag='item'); [print(item.find('enclosure').get('url')) for item in items]"))
rm -rf $tmp

length=$[${#array[@]}-1]

for i in `seq $length -1 0`;do
  idx=$(printf "%04d" $[${length}-${i}])
  echo "${idx};${array[$i]}"
done | xargs -n 1 -P $threads -I {} bash -c 'download "$@"' _ {}