Podcasting is delivering audio content to iPods and other portable media players on demand, so that it can be listened to at the user's convenience. The main benefit of podcasting is that listeners can sync content to their media player and take it with them to listen whenever they want to. Because podcasts are typically saved in MP3 format, they can also be listened to on nearly any computer.
The term podcasting was popularized by media entrepreneur and former MTV VJ Adam Curry. Curry created an Apple script application that automated the process of downloading and syncing audio files to iPods.
Curry's application built on the work of programmer Dave Winer, a pioneer in both the world of web logs and XML development. Winer wrote the RSS 2.0 specification, which is used to deliver information about podcasts. RSS is an XML format that is used to define channels of information that contain elements, which are typically stories or web log entries.
RSS files are often used as a standardized way of publishing Meta information about content. For example, web logs are typically user's thoughts about news stories or other web content.
RSS 2.0 supports enclosures, which are URL references to web content. This makes it possible to use RSS files to provide information about web content in a standard XML-based format. Podcasts are simply the application of RSS enclosures to audio files.
Podcasting has been described as TiVo for Internet audio, because it lets users save content digitally, and replay it at their convenience. This comparison, though, only addresses the idea of time-shifting, and not the idea that podcasting lowers barriers to entry, creates an alternate distribution model for audio content or that it lets publishers extend the reach of Internet content to times when people aren't even connected.
Podcasting can be used for publishing any type of audio, and some developers are exploring the idea of using the same techniques to publish video and other types of content.
Podcasting is spreading quickly because of the rapid adoption of MP3 players, and the desire of owners to have fresh content.
MP3’s
MPEG-1 Audio Layer 3, more commonly referred to as MP3, is a digital audio encoding format.
This encoding format is used to create an MP3 file, a way to store a single segment of audio, commonly a song, so that it can be organized or easily transferred between computers and other devices such as MP3 players.
MP3 uses a lossy compression algorithm that is designed to greatly reduce the amount of data required to represent audio recordings, yet still sound like faithful reproductions of the original uncompressed audio to most listeners. An MP3 digital file created using the mid-range bitrate setting of 128 kbit/s results in a file that is typically about 1/10th the size of the CD file created from the same audio source.
MP3 is an audio-specific format. It was invented by a team of international engineers at Philips, CCETT (Centre commun d'études de télévision et télécommunications), IRT, AT&T-Bell Labs and Fraunhofer Society, and it became an ISO/IEC standard in 1991. The compression works by reducing accuracy of certain parts of sound that are deemed beyond the auditory resolution ability of most people. This method is commonly referred to as Perceptual Coding.
It provides a representation of sound within a short term time/frequency analysis window, by using psychoacoustic models to discard or reduce precision of components less audible to human hearing, and recording the remaining information in an efficient manner. This is relatively similar to the principles used by, say, JPEG, an image compression format.
