generate_personal_podcast.rb

#!/usr/bin/env ruby -wKU
#
# by Kelan Champagne
# http://yeahrightkeller.com
#
# A script to generate a personal podcast feed, hosted on Dropbox
#
# Inspired by http://hints.macworld.com/article.php?story=20100421153627718
#
# Simply put this, and some .mp3 or .m4a files in a sub-dir under your Dropbox
# Public folder, update the config values below, and run the script.  To get
# the public_url_base value, you can right click on a file in that folder
# in Finder, then go to Dropbox > Copy Public Link, and then remove the
# filename.
#
# Notes:
#  * You'll need to re-run it after adding new files to the dir, or you can
#    set up Folder Actions as suggested by the above hint (sample AppleScript
#    in comments at the bottom of this file).
#  * This script uses `mdls` to get the title and summary of the podcast
#    from the Spotlight metadata, which requires it to be run on a Mac. But,
#    the rest of the script should be cross-platform compatible.

require 'date'


# Config values
podcast_title = "My personal podcast"
podcast_description = "My personal podcast description"
public_url_base = "<put the public url to your dropbox folder here>"


# Generated values
date_format = '%a, %d %b %Y %H:%M:%S %z'
podcast_pub_date = DateTime.now.strftime(date_format)

# Build the items
items_content = ""
Dir.entries('.').each do |file|
    next if file =~ /^\./  # ignore invisible files
    next unless file =~ /\.(mp3|m4a)$/  # only use audio files

    puts "adding file: #{file}"

    item_size_in_bytes = File.size(file).to_s
    item_pub_date = File.mtime(file).strftime(date_format)
    item_title = `mdls --name kMDItemFSName "#{file}"`.sub(/^.*? = "/, '').sub(/"$/, '').chomp
    item_subtitle = `mdls --name kMDItemAuthors "#{file}"`.sub(/^.*? = \(\n\s*/, '').sub(/\n\s*\)$/, '').sub(/.*null\)/, '').chomp
    item_summary = `mdls --name kMDItemDisplayName "#{file}"`.sub(/^.*? = "/, '').sub(/"$/, '').sub(/.*null\)/, '').chomp
    item_url = "#{public_url_base}/#{file}"
    item_content = <<-HTML
        <item>
            <title>#{item_title}</title>
            <itunes:subtitle>#{item_subtitle}</itunes:subtitle>
            <itunes:summary>#{item_summary}</itunes:summary>
            <enclosure url="#{item_url}" length="#{item_size_in_bytes}" type="audio/mpeg" />
            <pubDate>#{item_pub_date}</pubDate>
            <guid>#{item_url}#{podcast_pub_date}</guid>
        </item>
HTML

    items_content << item_content
end

# Build the whole file
content = <<-HTML
<?xml version="1.0" encoding="ISO-8859-1"?>
<rss xmlns:itunes="http://www.itunes.com/dtds/podcast-1.0.dtd" version="2.0">
    <channel>
        <title>#{podcast_title}</title>
        <description>#{podcast_description}</description>
        <pubDate>#{podcast_pub_date}</pubDate>
#{items_content}
    </channel>
</rss>
HTML

# write it out
output_file = File.new("podcast.rss", 'w')
output_file.write(content)
output_file.close

# = Sample AppleScript to auto-run this script. = 
# This AppleScript also touches the new file so that it's modification 
# date (and thus the pubDate in the podcast) are the date/time that you 
# put it in the folder.
#
# To install:
# - Open AppleScript Editor and copy-paste the below code (minus #'s)
# - Save the script to "/Library/Scripts/Folder Action Scripts"
# - Control-click the podcast folder, "Services > Folder Actions Setup"
#   and choose your script 
#
#on adding folder items to this_folder after receiving added_items
# 	set the_folder to POSIX path of this_folder
# 	set the_folder_quoted to (the quoted form of the_folder as string)
# 	
# 	repeat with this_item in added_items
# 		set the_item to POSIX path of this_item
# 		set the_item_quoted to (the quoted form of the_item as string)
# 		do shell script "touch " & the_item_quoted
# 	end repeat
# 	
# 	tell application "Finder"
# 		display dialog "cd " & the_folder_quoted & ";./generate_personal_podcast.rb"
# 		do shell script "cd " & the_folder_quoted & ";./generate_personal_podcast.rb"
# 	end tell
# 	
# end adding folder items to

I made a version that uses ffprobe for retrieving correct metadata from media files, instead of the mostly empty Spotlight tags:
fork