Non-zero consistent black areas in stream module output

[t-sasatani]

As described in #99, some videos output by the stream module have areas where the pixel values are consistent with 16 (found by @MarcelMB).

This could be the following black padding function somehow getting messed up in later stages.

mio/mio/stream_daq.py

Lines 206 to 212 in 56397e9

	if data.shape[0] != expected_data_size:
	# trim if too long
	if data.shape[0] > expected_data_size:
	data = data[0:expected_data_size]
	# pad if too short
	else:
	data = np.pad(data, (0, expected_data_size - data.shape[0]))

Otherwise, it could be that the input data stream contains continuous 16s, some glitch in bit operation, etc. I'll look into the FPGA output binaries for this to confirm.