A podcast is
a multimedia file that is distributed
by subscription (paid or unpaid) over
the Internet using syndication feeds,
for playback on mobile devices and personal
computers. Like 'radio', it can mean
both the content and the method of broadcast.
The latter may also be termed podcasting.
The host or author of a podcast is often
called a podcaster (Christ
Embassy in this case) .
The concept of podcasting
was suggested as early as 2000 and its
technical components were available by
2001, then implemented in the program
Radio Userland. In 2003 regular podcasts
started showing up on well-known Web
sites and software support spread.
Mechanics
The publish/subscribe model
of podcasting is a version of push technology,
in that the information provider chooses which
files to offer in a feed and the subscriber chooses
among available feed channels. While the user
is not "pulling" individual files from
the Web, there is a strong "pull" aspect
in that the receiver is free to subscribe to
(or unsubscribe from) a vast array of channels.
Earlier Internet "push" services (e.g.,
PointCast) allowed a much more limited selection
of content.
Podcasting is an automatic
mechanism whereby multimedia computer
files are transferred from a server to
a client, which pulls down XML files
containing the Internet addresses of
the media files. In general, these files
contain audio or video, but also could
be images, text, PDF, or any file type.
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 list of the URLs by which
episodes of the show may be accessed.
This list is usually published in RSS
format (although Atom can also be used),
which provides other information, such
as publish date, 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. Standard podcasts
consist of a feed from one author. More
recently multiple authors have been able
to contribute episodes to a single podcast
feed using concepts such as public podcasting
and social podcasting.
A podcast specific aggregator is usually an always-on
program which starts when the computer is started
and runs in the background. They work exactly
like any newsreader someone would use to manage
other web subscriptions. 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 application's list), the
program determines the location of the most recent
item and automatically downloads it to the user's
computer. Interestingly, it is estimated that
perhaps only 20% of podcasts are actually consumed
on portable media players; 80% are consumed on
the PC onto which they are downloaded, or deleted
from the PC without being listened to. Some applications,
such as iTunes, also automatically make the newly
downloaded episodes available to a user's portable
media player.
The downloaded episodes
can then be played, replayed, or archived
as with any other computer file.
To conserve bandwidth,
users may opt to search for content using
an online podcast directory. Some directories
allow people to listen online and initially
become familiar with the content provided
from an RSS feed before deciding to subscribe.
For most broadband users, bandwidth is
generally not a major consideration;
it could fairly be stated that podcasting
itself is a technology that came with
the increases in global bandwidth and
broadband popularity.
Uses
of Podcasting
Podcasting's initial appeal was to allow individuals
to distribute their own "radio shows," but
the system quickly became used in a wide variety
of other ways, including distribution of school
lessons , official and unofficial audio tours
of museums, conference meeting alerts and updates,
and by police departments to distribute public
safety messages. The Christ Embassy Podcast Project
provides dynamically generated podcasts from
5 selected Pastor Chris' TV and Radio programs,
all in English language, and delivered to the
desktop of millions of subscriber all over the
world.
To
Subscribe To Pastor Chris Podcasts, CLICK HERE