The AVR UC3 series microcontroller requires very few external components to decode and play back digital audio. The USB line drivers and PHY are integrated into some versions of the UC3 AVR microcontroller to communicate with a media player, USB flash disc, or computer. The sound is outputted either through the I2S or via the internal audio DAC. If the internal audio DAC is used, the only external component needed is a class D amplifier before the speaker. The I2S interface can also be used to stream the audio to an external I2S DAC or sound shaping module if desired. These are the basic components of a digital audio player. There are a lot of possibilities when it comes to extensions; LCDs for GUIs, Data Flash for storage, and RAM for buffers and graphics. Control mechanisms can be added as well as wired networks. With the possibility to also add a series of wireless protocols such as WLAN, Bluetooth and ZigBee, the AVR is the natural choice for many audio applications.