Pioneer Android Auto & Wireless Android Auto Stereos for your 2013 A4

RCA Composite Inputs
These are your typical red, white, and yellow RCA composite cables that are common among devices with audio and video inputs. The red and white cables are dedicated for audio. The red cable is for the right channel and the white is for the left channel. The yellow cable is specifically for the video signal. Because this type of auxiliary cable contains 2 channels of audio, it will support stereo sound.

3.5mm
This is commonly referred to as a mini-jack or a headphone jack. It is a 3.5mm plug that transfers audio only. There is a right and left audio channel on the plug which allows for stereo sound playback.

3.5mm AV Input
These plugs look similar to the common 3.5mm mini-jack, however they carry a third channel dedicated for video.

Optional
This means that an auxiliary input is possible, but only with the use of an optional accessory. These optional adapters will sometimes use the CD Changer port or other port on the back of a unit that might restrict the use of other expandability features. These accessories are typically sold separately.

RCA Composite Outputs
These are your typical red, white, and yellow RCA composite cables that are common among devices with audio and video inputs. The red and white cables are dedicated for audio. The red cable is for the right channel and the white is for the left channel. The yellow cable is specifically for the video signal. Because this type of auxiliary cable contains 2 channels of audio, it will support stereo sound.