There are dozens of computer applications that play back digital audio--far more than could be covered sufficiently in this book--so I will highlight four freely distributed proprietary players that are often used with digital audio projects as well as one open-source player that is a good alternative choice for libraries that offer digital sound in multiple formats.
To test the capabilities of the players, I took sample files in five formats--MP3, RealAudio, Windows Media Audio, AAC (in both an MPEG-2 and an MPEG-4 format file), and Ogg Vorbis--and attempted to play them on the latest version of each player, as it is, ``out of the box,'' without importing additional codecs. The table in figure 4.1 summarizes the results.4.6
From this table, it would be easy to conclude that MP3 is the ideal format (since it can be played by all the players) and VLC the ideal player (since it can play all the formats), but the situation is a bit more complicated than that. Other formats provide better fidelity than MP3 at similar bitrates,4.7 and the support community for VLC is far smaller than for the proprietary players.
Many of the popular proprietary players--such as Windows Media Player, RealPlayer, and QuickTime Player--are also designed to serve as media content browsers to access news reports, videos, shopping sites, and so forth. Like iTunes, they can also synchronize content with portable digital players and connect directly to digital music stores, where use licenses can be purchased for individual tracks. The latest version of Windows Media Player and RealPlayer can also play DVDs. These extra features add to the size of the application and the demands placed on computer resources. Unless these added features are needed by your users, they will be best served by a stripped down, freely distributed ``basic'' version of the player, which will load more quickly and perform more reliably than the full-featured versions.
In this section, we will look only at the functionality of the players for playing back audio. The use of other features of the players--such as ripping CDs and encoding files--will be covered elsewhere.
