All PMPs invariably support MP3 audio, so that music can be easily swapped from your computer to your PMP and back, as MP3 is one of the most popular formats with a huge volume of existing media. Other formats supported are Microsoft’s WMA and also the open source Ogg Vorbis. WMA reduces the size of MP3 files by almost a factor of two, but due its proprietary nature, costs could increase. Ogg is technically superior in terms of compression, but lack of availability of media can be a problem.
AAC (Advanced Audio Coding) is a lossy compression and coding scheme for audio, and is touted to be the successor to MP3. AAC delivers better quality than MP3 at the same bitrate. AAC is the standard format used on the iPod and the iTunes store, and in the PlayStation 3. Other music players that support AAC include the Creative Zen and Microsoft’s Zune.