SDK / exoplayer

- Have extractors read from an ExtractorInput. Benefits of this are
  (a) The ability to do a "full" read or skip of a specified number
  of bytes, (b) The ability to do multiple reads in your extractor's
  read method. The ExtractorInput will throw an InterruptedException
  if the read has been canceled.

- Provides the extractor with the ability to query the absolute
  position of the data being read in the stream. This is needed for
  things like parsing a segment index in fragmented mp4, where the
  position of the end of the box in the stream is required because
  the index offsets are all specified relative to that position.