To hit 300MB, audio is almost always compressed to AAC 2.0 Stereo at 96kbps or 128kbps. You will never find 5.1 surround sound or lossless DTS-HD in a 300MB file. The stereo, however, is perfectly fine for laptop speakers or earbuds.

The first major standard was the 700MB XviD AVI, designed to fit on a single CD-R.