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JS Podcatcher (a Podcast client written in JavaScript)

Posted by bcmoney on November 29, 2014 in HTML, JavaScript, Multimedia, TV with No Comments

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English: The "Made for iPod, iPhone, iPad...

English: The “Made for iPod, iPhone, iPad” emblem appearing on accessories approved by Apple Inc. for iPod, iPhone, and iPad. (Photo credit: Wikipedia)

So just this month my 5-year old iPhone3GS finally bit the dust. I had been hanging on and managed to extend its life well beyond its 3-year Telco contract (which I immediately cancelled the day I was out) by pairing it with a MiFi hotspot for much cheaper VoIP-based calling and using data-intensive applications only when on WiFi. That trusty iPhone3GS made it through a major liquid submersion (thanks to the good folks at Atlantic Cell Phone Repair) two cracked screens (thanks to the good folks at iCracked). At some point I may even replace the screen again, which is what’s gone a third time. I’m pretty stubborn though, and now that I’ve finished off my Mobile contract for the MiFi as well, pretty much at all costs I really didn’t want to have to buy another discounted device which usually requires one to agree to the terms of a foolishly one-sided/restrictive 2-year or 3-year contract; likewise, I really don’t want to shell out anywhere near the full asking price in the $500-$1000 price range for a new smartphone. So it’s either go back to my old Nokia flip-phone and live in the early 2000’s on a basic voice-calling only plan, or, hack my old 4th generation iPod Touch into something with phone call abilities. Of course, I opted for the latter!

iPhone 3G and iPod Classic 5G.

iPhone 3G and iPod Classic 5G. (Photo credit: Wikipedia)

Luckily thanks to an excellent VoIP app called BRIA (of which a 4th gen. iOS 4 version is still available in the iTunes App Store), I was able to continue doing voice calling by using my Anveo VoIP service (highly recommend this low-cost VoIP provider, please enter Referral Code 5334764 if registering). I was already using Anveo through BRIA on the iPhone, over MiFi when on-the-go, for over a year and a half since I got out of that first contract. I’ve described Anveo in great detail in “My Experiment in Cutting Cords (and costs) with VoIP” where I went over setting the VoIP service up on an iPhone (with BRIA app) and just how much could actually be saved per month by taking the plunge and switching to VoIP instead of a traditional Telco calling/data plan. I’ve found that with a little patience and using replacements (such as Slingplayer in place of Bell MobileTV, or, SoundHound in place of Shazam) along with some occasional disappointment (can’t get older versions of Netflix, Skype, Fitocracy, and several other top apps), I was able to get a good amount (about half) of the apps I was most frequently using on my iPhone3GS, downloaded to the iPod4th gen, in their older iOS 4-supported versions.

One somewhat irreplaceable app though that I just simply could not find, nor find a replacement for was the basic “Podcasts” app built by Apple (common alternatives such as Overcast, Downcast, TuneIN, Slacker, and even RSSradio all did not work on my device either). I mean, seriously Apple, WTF!? Even the very first iPod devices were within a few years of their release to become known as the cannonical “Podcatcher” (Podcatcher means a podcast downloader/player).

The term “podcasting” itself was first mentioned by Ben Hammersley in a February 2004 article in The Guardian newspaper as a portmanteau of the words “pod”, from the success in consumerizing digital music with the “iPod” line of Apple products and “broadcast” (as in traditonal Radio/TV broadcasting to many receivers over a wide area, constantly). As such, the native “Podcasts” app has been around since the early days, as Podcatching (better known as receiving and listening to Podcasts), became one of the main functions of iPods just as it continues to be a core functionality on the many other iOS devices. Why then, are older (iOS < 6) versions of the Podcasts app not still available through the iTunes App Store? The app existed back then, for those devices, and now its just plain unavailable it seems. Why not keep the old versions around? What if a legacy iPod user (anyone still on iOS 4 or lower for that matter) accidentally wipes or restores their device to factory settings? Tough luck if they didn’t store a backup that had that legacy version of the app which still runs on their device. This is an example of planned obsolescence at its worst!!!

Apple be damned, could the Podcast app’s functionality be replaced with a quickly hacked together web app though? Being a developer, that’s the question I wanted an answer to. So I realized it definitely should be doable, as Podcasts to me have always simply been RSS news feeds with links to Audio files embedded in them in a variety of ways. Thanks to Apple’s aforementioned “Podcatching” dominance, and iTunes’ position of oligopoly, Podcasts also need to be garnished with plenty of Apple-specific syntactic metadata to satisfy the behemoth that is the iTunes Store and rank better therein, so have to be able to parse that crap too.

All that to set the context for this experiment, which aims to concisely (I promise hah, from here on) describe how I took my original RSS parser from the post “RSS Reader in jQuery .vs. JavaScript”) on using JavaScript and/or jQuery to implement an RSS news reader, and modified it a few weeks ago to allow me to read the media links and embed codes.

I needed to add some conditional checks for the different ways of publishing the actual audio/video files shared by podcasts and vodcasts, respectively which differ between not just type of content (Podcast/Vodcast) but also between individual content publishers of the Podcast/Vodcast sources. What I found was that these variations amongst Publishers included using the <guid> element (RSS 1.0), other times using the url attribute of the <enclosure> (RSS 2.0), or other times still using the url attribute of the <media:content> (mRSS) element. All different XML elements and attributes to share the same basic thing, the location of their media files for playback (or in laymans terms, “the goods”). Here’s the simple modification:

function parsePodcast(data, limit) {
	var rss = data.getElementsByTagName("rss");		//<rss>
	  //Parse RSS Feed channel properties
	  channel = data.getElementsByTagName("channel");							//<channel>
	  title = data.getElementsByTagName("title")[0].childNodes[0].nodeValue;		//<title>
	  link = '#';
	  try {
		link = data.getElementsByTagName("link")[0].childNodes[0].nodeValue;		//<link>
	  } catch (ex) { }
	  description = data.getElementsByTagName("description")[0].childNodes[0].nodeValue; //<description>
	  image_url = 'podcast.png', image_link = '#', image_html=title+' (RSS Feed)';
		image = data.getElementsByTagName("image")[0];					//<image> (optional RSS element)
		if (!empty(image)) {
                    try {
		      image_url = image.getElementsByTagName("url")[0].childNodes[0].nodeValue;		//<url>
		      image_link = image.getElementsByTagName("link")[0].childNodes[0].nodeValue;	//<link>
                    } catch(ex) { }	
		iTunesImage = '';
		try {
			iTunesImage = data.getElementsByTagName("itunes:image")[0];					//<itunes:image> (optional RSS element)
			if (!empty(iTunesImage)) {
				image_url = iTunesImage.getAttribute("href");		// ... href=""		
		} catch (ex) { }
   	      //language = data.getElementsByTagName("language")[0].childNodes[0].nodeValue;//<language>
		  //copyright = data.getElementsByTagName("copyright")[0].childNodes[0].nodeValue;	//<copyright>
          //lastBuildDate = data.getElementsByTagName("lastBuildDate")[0].childNodes[0].nodeValue; //<lastBuildDate>
          //docs = data.getElementsByTagName("docs")[0].childNodes[0].nodeValue;	  		//<docs>
          //ttl = data.getElementsByTagName("ttl")[0].childNodes[0].nodeValue;				//<ttl>		
		  metadata = '<div style="display:block; clear:both;"><a href="'+link+'" class="external">'+'<img width="20%" src="'+image_url+'" title="'+title+'": "'+description+'" style="vertical-align:middle;"/>'+'</a></div>';//"<br/>" + lastBuildDate + " | " + copyright + "<br/>Following spec at: " +  docs + " | Cache for: " + ttl + " | " + language + "<div style="clear:both;">&nbsp;</div>";      

	  //Parse RSS Feed items 
      items = data.getElementsByTagName("item"); 											//<item>
      news = metadata+"<nav><ul>";
      for (i = 0; (i < items.length && i < limit); i++) {	  	
           title = items[i].getElementsByTagName("title")[0].childNodes[0].nodeValue;	  		  //<title>
			guid = items[i].getElementsByTagName("guid")[0].childNodes[0].nodeValue;				  //<guid>	
				id = !empty(guid) ? guid : title.substring(0,12)+'-'+item;					//unique ID
		   image = 'podcast.png';
			try {
				pic = items[i].getElementsByTagName("media:thumbnail")[0].getAttribute("url");  		  //<media:thumbnail> (image) mRSS2.0 only
					image = !empty(pic) ? pic : 'podcast.png';
			  catch (ex) {
			link = '#';		  		  //<link>
			try	{
				link = items[i].getElementsByTagName("link")[0].childNodes[0].nodeValue||'';		  		  //<link>				
			  catch (ex) {
           pubDate = items[i].getElementsByTagName("pubDate")[0].childNodes[0].nodeValue;		  //<pubDate>
		   desc = items[i].getElementsByTagName("description")[0].childNodes[0].nodeValue; //<description>		  
				description = desc.replace(/&lt;/gi,'<').replace(/&gt;/gi,'>');		   
		   audio = '#'; //AUDIO file
				try	{					
					audio = items[i].getElementsByTagName("enclosure")[0].getAttribute('url');		//RSS 2.0
				} catch (ex) {
					try {
						audio = items[i].getElementsByTagName("media:content")[0].getAttribute('');		//mRSS and iTunes <media:content url="..."/>
					} catch (ex) {					
						audio = guid;																//RSS 1.0
			player = '';
				if (getFileExtension(audio)) {
					player =  '<audio controls><source src="'+audio+'" type="audio/mpeg">Player unable to play media file or non-HTML5 browser.</audio>';
		   news += '<div class="article"><a href="#lb'+i+'" title="Click once for summary, twice to visit source..."><img class="icon" src="'+image+'" alt="'+title+'" /> '+title+'</a><div id="lb'+i+'" class="lb"><a class="external" href="'+link+'"><img src="'+image+'" alt="'+title+'" /></a><a href="#top" class="close"><img src="close.gif" alt="Close" /></a><div class="story">'+description+player+'</div></div></div>';
	  news += "</ul></nav>";
	return news;

You can try it out or download the code below:


The demo works by taking a particular podcast’s web URL (for the marked-up RSS podcast feed) and putting it in the “Add” podcast field by hitting the “+” icon, then entering it, then clicking the “Add” button. The podcast being displayed will then immediately reload. The default limit set for number of podcast feed items to display is 20 (however this is easily adjusted). This limit was put in place because some podcast feeds actually list all podcast archives going back to their first show which can result in slow load times as the entire data file gets loaded and processed. Aside from the slow load it could be a large corresponding data plan hit when loading via Mobile network, especially if the podcast has been around for a while and lists all past podcast archives in their main feed. If it publishes updates infrequently, then the content should be cached.

Since this post was auto-scheduled quite some time ago and I’ve been busy with work and life, I completely forgot to get around to adding a few other features around those limitations that I wanted in my JS Podcatcher. Those are, namely:

  1. the ability to add multiple podcasts where each one is clickable/draggable to sort, and shows a feed like the basic Podcasts app.
  2. capability to auto-save those Podcasts so that your entire Podcast list is remembered past the lifetime of a single Page or Session.
  3. cache and synchronize the Podcasts client-side using Offline, localStorage and/or WebSQL APIs to save data loading size/costs and not reload unless new Podcast episodes are available on the client (and/or server, possibly even parse feed server-side and inject a single episode at a time to the client).
  4. integration of my already developed iTunes API connector code, which would enable users to search through iTunes for specific podcast URLs for convenience.
  5. the audio files are embedded in HTML5 audio, however if that fails I should put an embedded Flash player fallback in its place instead of just a download link to the media file. This would cover non-iOS mobile devices that don’t currently work (such as my Playbook) which may support Flash but not HTML5 fully.

But it works for me, for now, since I’ve bookmarked a link which lists all my podcasts URLs, and should work for you too if you do something similar and list out the URLs somewhere one time and copy/paste as needed. Podcasts are now coming in great on my iPod 4th gen!!! The most frustrating thing is probably that you can only listen to one Podcast audio file at a time and can’t manage several. However, thanks to the way the human ear works (unless you have some kind of uncanny abilities that might qualify as super-powers) you can only listen to one at a time anyway so should be plenty.

That said, for completeness, stay tuned for a follow-up post if I ever get around to adding those five features above, and possibly clean up the user experience a bit.