From the ALSA wiki
A frame is a set of samples, one per channel, at a particular instant in time. For stereophonic audio, a frame consists of two samples. For Dolby 5.1 Surround Sound, a frame would consist of six samples (left channel, center channel, right channel, rear right, rear left, and the low frequency channel). For monophonic audio, a frame is equivalent to one sample.
Retrieved from "http://alsa.opensrc.org/Frame"