23 October 2005

mp3, mp4, m4a, m4b, m4v

There was a time when the format used by podcasters was just .mp3 for "audio pocasts" but those days are gone! While the .mp3 format is still extremely popular, the advent of new variations of the codec based on the .mp4 layer are gradually becoming more common.

So what are these codecs and how do they affect podcasting?

As usual, the codecs come in a variety of forms and very much depend on the focus of the podcast. The .m4a format (known as AAC) generally provides a better audio compression than a .mp3 codec on a like for like basis. For any format other than a .mp3 in our podcast directory, we now clearly identify the format of each podcast using one of the following symbols:

for podcast using the AAC format

for podcasts with chapters and images (as in audiobooks)

for vodcasts using the codec for movie files compatible with video iPods

for vodcasts using this general video format

for vodcasts using this traditional video format

In this transition stage until there is both a wider awareness amongst the podcast community and some common approach emerges, you may find that some podcasts that we list may be identified as .m4a may also contain either chapters or images or a mixture. To a large extent this very much depends on the application of encoding techniques by podcasters.

Podcasts using the .m4b codec are often known as "enhanced podcasts" because they contain both chapters and images. As mentioned above, some .m4a enhanced podcasts may have incorrectly used the .m4a codec instead of the .m4b format designed for this purpose.

Podcasts that use the .m4v or .mp4 formats are often "video podcasts" or vodcasts. These will always display as vodcasts as those that have used the traditional .mov format have always done.

For a technical overview of these various formats visit Wikipedia. Who ever said that life was straightforward in the world of information and communication technologies?