MP3 Audio Parser
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This element acts as a parser for mpeg audio data.  It's called 'mp3' but
in reality will work for any MPEG-1, MPEG-2, or MPEG-2.5 elemental audio
stream of any of Layers I, II, and III.  It will not (currently, ever?)
handle MPEG-2 BC or NBC streams, as those have rather specialized needs
best served be a different filter.

It will take an mpeg audio stream in any form on its 'src' input, with any
buffer size, and split it into buffers containing a single frame each.
NOTE: ancillary data is not dealt with right now.