Parses the file band headers (not including the actual bits themselves).
At the end of this parse call, the input stream will be positioned at the
start of the file_bits themselves, and there will be Sum(file_size) bits
remaining in the stream with BYTE1 compression.
A run codec is a grouping of two nested codecs; K values are decoded from
the first codec, and the remaining codes are decoded from the remaining
codec.