*
* input: stream of bits, 1 bit per input byte (data in LSB)
* output: stream of bits, 2 bits per output byte (data in LSB, flag in next higher bit)
*
* input: stream of bits, 1 bit per input byte (data in LSB)
* output: stream of bits, 2 bits per output byte (data in LSB, flag in next higher bit)