Podcasting is a term used to describe a collection of technologies for automatically distributing audio and video programs over the Internet using a publisher/subscriber model. It differs from earlier online collections of audio or video material because it automatically transfers materials to the user's computer for later consumption; it is one example of push technology. Podcasting enables independent producers to create self-published, syndicated "radio shows," and gives broadcast radio or television programs a new distribution method.
Any digital audio player or computer with audio-playing software can play podcasts. From the earliest RSS-enclosure tests in 2000 and 2001, feeds have been used to deliver video files as well as audio, and other media such as photographs and text are transferable by podcast. The term "podcast", however, still refers largely to audio content distribution.
A podcast is not the same as a webcast, which normally refers to a show distributed by streaming media.
"Podcasting" is a portmanteau that combines the words "iPod" and "broadcasting."
The term is often thought to be a misnomer since neither podcasting nor listening to podcasts requires an iPod or any portable player, and no broadcasting is required. The term is also sometimes criticized as giving undue credit to Apple for a technology which it had very little to do with creating. Aware of this potential misunderstanding, some writers have suggested alternative names. One such alternative is "blogcasting", which implies content based on, or similar in format to, blogs. Others include "audioblogging" and "rsscasting". Some writers have also suggested reinterpretations of "pod", such as "Personal, On-Demand" or phonetically "Portable Audio".[1]
Podcasting as a medium is not limited to audio data. Podcasting of video data is called, among other things, "video blogging" (see vlog), "video podcasting", "vlogging", "vodcasting", or "vidcasting".
Podcasting is an automatic mechanism by which computer files are transferred from a server to a client which pulls down XML files containing the addresses of the media files. In general, these files contain audio or video, but also could be images, text (e.g. PDF), or any file type.
A podcast is generally analogous to a (non-live) television or radio series.
The content provider begins by making a file (for example, an MP3 audio file) available on the Internet. This is usually done by posting the file on a publicly-available webserver; however, BitTorrent trackers also have been used, and it is not technically necessary that the file be publicly accessible. The only requirement is that the file be accessible through some known URI (a general-purpose Internet address). This file is often referred to as one episode of a podcast.
The content provider then acknowledges the existence of that file by referencing it in another file known as the feed. The feed is a machine-readable list of the URIs by which episodes of the show may be accessed. This list is usually published in RSS format, which provides other information, such as publish dates, titles, and accompanying text descriptions of the series and each of its episodes. The feed may contain entries for all episodes in the series, but is typically limited to a short list of the most recent episodes, as is the case with many news feeds.
The content provider posts the feed to a known location on a webserver. (Unlike the episode file itself, the feed is published to a webserver, usually not by other means.) The location at which the feed is posted is expected to be permanent. This location is known as the feed URI (or, perhaps more often, feed URL). The content provider makes this feed URI known to the intended audience.
A consumer enters this feed URI into a software program called a podcatcher or aggregator (the former term is specific to podcasting while the latter is general to all programs which collect news from feeds). This program retrieves and processes data from the feed URI.
A podcatcher is usually an always-on program which starts when the computer is started and runs in the background. It manages a set of feed URIs added by the user and downloads each at a specified interval, such as every two hours. If the feed data has substantively changed from when it was previously checked (or if the feed was just added to the podcatcher's list), the program determines the location of the most recent episode and automatically downloads it to the user's computer. Some podcatchers, such as iTunes, also automatically make the newly downloaded episodes available to a user's portable media player. (This is only the typical behavior of a podcatcher; some podcatchers behave—or can be set to behave—differently.)
The downloaded episodes can then be played, replayed, or archived as with any other computer file.
Unlike streaming media, podcasting is not live data transfer. Streaming media is more like traditional broadcast radio and television, while subscribing to a podcast is closer to joining a CD-of-the-month club.
Podcasting provides a more suitable means of transferring high-quality content to users with low-bandwidth connections; low data rates and high latency do not adversely affect the quality of the content as they do with streaming.
Programs distributed by podcasting are not transient; streamed programming is. With streaming media one must capture data as it is received, while a podcast episode is received already in archived form. (This distinction makes a podcast legally distinct from a streamed webcast.)
By 2003, web radio had existed for a decade, digital audio players had been on the market for several years, blogs and broadcasters frequently published MP3 audio online, and RSS file formats were widely used for summarizing or syndicating Web content.
The RSS enclosure element required for podcasts was created in version 0.92 of RSS, published[2] in late 2000 by Userland Software's Dave Winer, spurred by a draft proposal from Tristan Louis[3] and by conversations with Adam Curry[4], as well as a request from Harold Gilchrist, another user of Userland blogging software. The ability to send and receive enclosures was incorporated in Radio Userland, which included an RSS aggregator as well as a weblog editor. Winer and Curry discussed the enclosure feature as a way to avoid having to wait for downloads of large video or audio files, by pre-fetching them overnight. Gilchrist put the program to the test early, audioblogging in January 2002 and using the RSS enclosure feature with MP3 files by October 2002. However, few other aggregator developers adopted the enclosure feature until 2004. (Ironically, the rival RDF Site Summary syndication format already supported media resources implicitly, although applications rarely took advantage of the feature.)
In June 2003, Stephen Downes demonstrated aggregation and syndication of audio files using RSS in his Ed Radio application [5]. Ed Radio scanned RSS feeds for MP3 files, collected them into a single feed, and made the result available as SMIL or Webjay audio feeds. In September 2003, Winer created an RSS-with-enclosures feed for his Harvard Berkman Center colleague Christopher Lydon, a former newspaper and television journalist and public radio radio talk show host. Since July, Lydon had been linking full-length MP3 interviews to his Berkman weblog, focusing on blogging itself and coverage of the coming 2004 U.S. presidential primary campaigns. In his announcement[6] of Lydon's audio-enclosure feed, Winer challenged aggregator developers to "be a leader, give your users the tools to be among the first to get the benefit of these great interviews, and the new content that's sure to follow." Some did. In September 2003 Pete Prodoehl released a skin for the Amphetadesk aggregator that displayed enclosure links.
At the first Harvard BloggerCon conference, October 4-October 5 2003, which Winer and friends organized, CDs of Lydon's interviews were distributed, and Kevin Marks demonstrated a script to download RSS enclosures to iTunes and synchronise them onto an iPod[7], something Curry had talked about doing with Radio Userland and his RSS2iPod Applescript. On October 12, 2003, Curry offered his blog readers the script as a way to "automagically update your iPod with any new mp3s that are downloaded to your Radio UserLand enclosures folder from enclosure aware RSS feeds." Curry has said he didn't attend Marks' presentation, but his participation in BloggerCon and listening to Lydon's interviews on an iPod apparently contributed to his interest in RSS attachments. Along with RSS2iPod, he created a feed that he named "syncpod", which was used for testing by Marks, Werner Vogels and other developers at the conference, some of whom became involved in open source iPodder development projects. Curry put his Applescript in open source and called it ipodder, at ipodder.org, and encouraged other developers to build on the idea. During this pre-podcasting period, Harold Gilchrist was also audioblogging with Radio Userland and evangelizing on a regular basis.
Possibly the first use of the term "podcasting" was as a synonym for audioblogging or weblog-based amateur radio in an article by Ben Hammersley in The Guardian on February 12 2004 [8]. The name wasn't widely adopted until that fall. In September, Dannie Gregoire used the term to describe the automatic download and synchronization idea that Curry had developed [9]. Gregoire had also registered multiple domain names associated with podcasting. That usage was discovered and reported on by Curry, Winer and Dave Slusher of the Evil Genius Chronicles website.
In July 2004, Winer posted audio of interviews he conducted at the Democratic National Convention to his Berkman RSS feed. On Friday the 13th of August, Curry launched his Daily Source Code podcast, and a month later started a Yahoo e-mail list for iPodder developers. The second message posted was from Pieter Overbeeke, a Dutch developer, who said he had spent the past month working on Windows, php and javascript alternatives to iPodder. In September Curry and Winer began a four-month collaboration on transatlantic podcast conversations they called Trade Secrets.
That summer, development of command-line based tools also included Dave Slusher's "get_enclosures" script, Pete Prodoehl's "renko", and Ray Slakinski's "pyPodder." In September, iPodderX, the first desktop-based podcast client, was developed by August Trometer and Slakinski, using "pyPodder" as the starting point. Other clients, including iPodder Lemon (later renamed Juice), followed soon after.
By fall 2004, audio blogging had emerged from obscurity, associated with the then-hot iPod and pushed ahead by Curry's RSS2iPod script and the programs it inspired.
By October 2004, detailed how-to podcast articles[10] had begun to appear online. In November 2004, liberated syndication libsyn launched what was apparently the first Podcast Service Provider, providing storage, bandwidth, and RSS creation tools.
Prior to the Internet, in 1970s, RCS, Radio Computing Service provided music and talk related software to radio stations in a digital format. Prior to online music digital distribution, the midi format as well as the M-Bone, Multicast Network was used to distribute audio and video files. The M-Bone was a multicast network over the Internet used primarily by educational and research institutes, but there were audio talk programs. Source: Publisher: National Association of Broadcasters, Internet Age Broadcaster I and II. Author: Peggy Miles and Dean Sakai
Many other jukeboxes and websites in the mid 1990's provided a system for sorting and selecting music or audio files, talk, sequeway announcements of different digtal formats. There were a few websites that provide audio subscription services.
The development of downloaded music did not reach a critical mass until the launch of napster.com, another system of aggregating music, but without the subscription services provided by podcasting or video blogging aggregation client or system software.
Independent of the development of podcasting via RSS, a portable player and music download system had been developed at Compaq Research as early as 1999 or 2000. Called PocketDJ, it would have been launched as a service for the Personal Jukebox or a successor, the first hard-disk based MP3-player. See appropriate section in the Personal Jukebox article.
The word about podcasting rapidly spread through the already-popular weblogs of Curry, Winer and other early podcasters and podcast-listeners. Fellow blogger and technology columnist Doc Searls began keeping track of how many "hits" Google found for the word "podcasts" on September 28 2004, when the result was 24 hits. [11] There were 526 hits for "podcasts" on September 30, then 2,750 three days later. The number doubled every few days, passing 100,000 by October 18. As of November 24, 2005 Google reported 103,000,000 hits for "podcasts".
Capturing the early distribution and variety of podcasts was more difficult than counting Google hits, but before the end of October, The New York Times reported podcasts across the United States and in Canada, Australia and Sweden, mentioning podcast topics from technology to veganism and movie reviews. [12] USA Today told its readers about these "free amateur chatfests" the following February [13] [14], profiling several podcasters, giving instructions for sending and receiving podcasts, and including a "Top Ten" list from one of the many podcast directories that had sprung up. The newspaper quoted one directory as listing 3,300 podcast programs in February, 2005.
Those Top Ten programs gave further indication of podcast topics: four were about technology (including Curry's Daily Source Code, which also included music and personal chat), three were about music, one about movies, one about politics, and—at the time number 1 on the list—The Dawn and Drew Show, described as "married-couple banter," a program format that USA Today noted was quite popular on American broadcast radio in the 1940s. Such "couplecasts" have since become quite popular among independent podcasts (those not derived from a preexisting radio show).
In March of 2005, John Edwards became the first national-level US politician to hold his own podcast [15]. (He may be the first major politician to have a podcast; given the nature of podcasting, we may never know.) Within a few episodes, the show had all the features of a major podcast: a web site with subscription feeds and show notes, guest appearances, questions from the audience, reviews and discussion of other media (in this case books), musical interludes of podsafe (noninfringing) songs, light banter (sports and recreation talk), even limited soundseeing from on location.
By mid-2005, the medium had acquired a bittersweet form of validation: a backlash. Some experienced Internet users declared podcasting to be either nothing special (just a variant of blogs and mp3s), or already past its peak (because of growing exposure, and/or adoption by unsavvy Internet users).
In June, 2005, Apple added podcasting to its iTunes 4.9 music software and iTunes Music Store, staking a claim to the medium. The iTunes software downloads and organizes podcasts, and loads them on the iPod, taking the place of a separate aggregator application. In addition, iTunes 5 interfaces with the online Music Store, which compiles and distributes the content. As of October 2005, the Music Store is free of charge to both the listener and creator.
A little over a month later, U.S. President George W. Bush became a podcaster[16], when someone added an RSS 2.0 feed to the previously downloadable files of the weekly radio addresses at the White House website.
As is often the case with new technologies, pornography has become a part of the scene - producing what is sometimes called podnography. Other approaches include enlisting a class full of MBA students to research podcasting and compare possible business models, [17] and venture capital flowing to influential content providers.
The growing popularity of podcasting introduced a demand for music available for use on the shows without significant cost or licensing difficulty. Out of this demand, a growing number of tracks, by independent as well as signed acts, are now being designated "podsafe". (See also Podcasting and Music Royalties.)
In September 2005, the first podcast encoded in full Dolby 5.1 Surround Sound, was created by Revision3 Studios with their 14th episode of Diggnation. The Dolby encoding lasted for only a few minutes of the podcast.
On October 12, 2005 Apple Computer CEO Steve Jobs unveiled the first iPod with video capabilty. In his keynote speech he demonstrated the video podcast Tiki Bar TV.
On December 03, 2005 Sony Computer Entertainment America unvailed that the PSP would have Podcasting using the RSS Channel feature. The PSP is able to use Podcasting by upgrading to 2.60. Sony
Traditional broadcasters were extremely quick to pick up on the podcasting format, especially those whose news or talk formats spared them the complications of music licensing. The American syndicated radio show Web Talk Radio[18] became the first to adopt the format, in September 2004, followed within weeks by Seattle news radio station KOMO and by individual programs from KFI Los Angeles and Boston's WGBH.
The BBC began a trial in October 2004 with BBC Radio Five Live's Fighting Talk. These trials were extended in January 2005 to BBC Radio 4's In Our Time[19]. Also in January 2005, CBC Radio began a trial with its weekly national science and technology show Quirks and Quarks[20], which has offered listeners Real Audio, MP3 and OGG downloads since February 1996. The CBC trial also included CBC Radio 3's Canadian Music Podcast as well as limited podcasting of CBLA's popular Metro Morning Toronto show. United States National Public Radio member stations WNYC and KCRW adopted the format for many of their productions. March saw Virgin Radio become the first UK radio station to produce a daily podcast of its popular breakfast show. In April 2005 the BBC announced it was extending the trial to twenty more programs, including music radio[21] and in the same month Australia's ABC launched a podcasting trial across several of its national stations[22].
In May, 2005, the trend began to go the other way, with podcasts becoming a source of content for broadcast radio programs by Adam Curry, Christopher Lydon and others. The entire format of KYOU Radio, a San Francisco radio station, became based around broadcasting Podcasts. That summer, when the Canadian Broadcasting Corporation locked out more than 5,000 of its regular on-air and technical staff, they responded by creating their own unofficial podcast of original programming, CBC Unplugged, which also appeared on some campus and community radio stations, including CIUT in Toronto and CFRU in Guelph, Ontario.
While podcasting's innovators took advantage of the sound-file synchronization feature of Apple Computer's iPod and iTunes software -- and included "pod" in the name -- the technology was always compatible with other players and programs. Apple was not actively involved until mid-2005, when it joined the market on three fronts: as a source of "podcatcher" software, as publisher of a podcast directory, and as provider of tutorials on how to create podcasts with Apple products GarageBand and Quicktime Pro.
When it added a podcast-subscription feature to its June 28, 2005, release of iTunes 4.9[23], Apple also launched a directory of podcasts at the iTunes Music Store, starting with 3,000 entries. Apple's software enabled AAC encoded podcasts to use chapters, bookmarks, external links, and synchronized images displayed on iPod screens or in the iTunes artwork viewer. Two days after release of the program, Apple reported one million podcast subscriptions.[24]
Some podcasters found that exposure to iTunes' huge number of downloaders threatened to make great demands on their bandwidth and related expenses. Possible solutions were proposed, including the addition of a content delivery system, such as liberated syndication; Podcast Servers;Akamai; a peer-to-peer solution, BitTorrent; or use of free hosting services, such as those offered by Ourmedia, BlipMedia and the Internet Archive.
As of September 2005, a number of services began featuring video-based podcasting including Apple via its iTunes Music Store and Loomia. Known by some as a vodcast, the services handle both audio and video feeds. As well as public broadcasting made possible by Participatory Culture Foundation.
Podcasting's initial appeal was to allow individuals to distribute their own "radio shows," but the system is increasingly used for other reasons, including:
From the beginning, the use of licensed music in podcasts has been a delicate legal issue. As was originally the case with streaming Internet radio, this new and infinitely more archivable form of media content would need to comply with as-yet unwritten rules.
Regular radio broadcasters' podcasts (and MP3 file downloads without subscription feeds) have run into complications regarding royalties for incidental music on "talk" broadcasts, even when identical programs are "streamed." The broadcasters apparently believe companies that license the music will challenge its use in easily downloaded MP3 files, while "streaming" is closer to a broadcasting model.
For example, when popular U.S. conservative commentator Rush Limbaugh began offering "podcasts" early in 2005, his employer, Premiere Radio Networks, tightened its editing of intro and bumper music, which it previously had allowed on other MP3 files. One effect was to render some of Premiere broadcaster Glenn Beck's podcasts difficult to follow. He would appear to stop mid-sentence and restart in a different thought, because of cuts required to remove royalty-protected music.
The US Congress is studying possible reforms to the Telecommunications Act of 1996, which may in the future affect broadband and Internet services.
As of December, 2, 2005, the following links point to a list of podcast search engines: