Added support for channels, changed samplerate so it doesn't return if doesn't exist. Made bitdepth only return if exists, looks like only mp4, flac and ape support bitdepth.
Added support for channels, changed samplerate so it doesn't return if
doesn't exist. Made bitdepth only return if exists, looks like only mp4,
flac and ape support bitdepth.

Original: 2e23e8204135353f00917f17b08a8f5344fd9e8a@9c70b26

beetbox/mediafile