This handy feature was originally created for audiobooks, but you can use it for any AAC podcast by simply changing the filetype of your audiofile from m4a to m4b. (Those same markers are not shown in the iTunes window, but instead, iTunes displays an extra menu called Chapters, which allows quick navigation to points in the podcast.)Ī simple trick with AAC files allows your iPod listeners to change the speed of the podcasts without changing the audio pitch. On an iPod, the chapter markers are graphically displayed on the timeline itself. These "chapter" markers can include a caption and an image, which are both accessible from an iPod or iTunes. An enhanced podcast adds markers to the track timeline, making it easier to locate interesting or specific segments. If you are a frequent listener of podcasts, you know the value of an enhanced podcast. The AAC format begins to shine when creating enhanced podcasts. The same podcast at 96kbps would be about 42MB - a considerable savings in size and therefore, download time. An hour-long podcast at 128kbps would be about 56MB. For example, if your acceptable podcast audio quality requires 128 kilobits per second (kbps) using MP3, you can probably settle on a 96kbps AAC encoding without loss in quality, thereby saving about 1/4 in file size. The quality of the audio files is usually expressed in the number of bits per second used to store audio information. This is important because podcasts are typically downloaded to the user's computer. So, let's look at the features of the AAC format that sway many podcasters.ĪAC encoded files can be smaller than MP3 encoded files. But the iTunes store only sells music in the AAC format.)įrom an acceptance point of view, the MP3 format is more prevalent, but you have take into account that iPods hold around 80% of the player market and many of the remaining 20% digital music players can also play AAC-encoded podcasts using the cross-platform iTunes software. (It is important to note that the iPod is also compatible with the MP3 format, among other formats. It has recently become much more widespread because it is the format of choice by the iTunes Music Store and the iPod. It is available on numerous devices and systems, making it the current standard. For a white paper on the formats, see MP3 and AAC Explained by Karlheinz Brandenburg of the Fraunhofer Institute, one of the inventors of the MP3 format. The Advance Audio Coding (AAC) definition is part of the MPEG-4 standard from around 1999 - which is why AAC is also referred to as MP4. The MPEG-1 standard, defined in 1991, had an audio component called MPEG-1 Layer 3, hence the confusing contractions to MP3. Both formats originate from the standards group MPEG (Moving Pictures Experts Group).
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