Major Description
In class AudioFrame the last two bits of the MPEG frame header are used to determine the number of channels. According to my documentation, this information is encoded in bits 7 and 6.
I did a cross check with the ID3 tag editor tool ID3-TagIT (http://www.id3-tagit.de/). The unit tests expect that the test MP3 files have 2 channels. However, the tool reports that the files are mono.