blend.py

#!/usr/bin/env python

import numpy as np
import sys

FRAME_SIZE = 1920*1080*3
BPC = 2
MAXINT = (256**BPC) - 1
GAMMA = 2.0  # A much faster approximation than 2.2

accum = np.zeros(FRAME_SIZE, dtype='f4')
count = 0
while True:
	data = sys.stdin.read(FRAME_SIZE*BPC)
	if len(data) < FRAME_SIZE*BPC:
		break
	frame = np.fromstring(data, dtype='<u2')
	accum += (frame.astype('f4')/MAXINT)**GAMMA
	count += 1
accum /= count
accum **= 1/GAMMA
accum *= 65535
accum.astype('<u2').tofile(sys.stdout)

blend.txt

ffmpeg -i BDMV.mov -f rawvideo -sws_flags print_info -vf format=yuv444p -pix_fmt rgb48le - | ./blend.py | ffmpeg -f rawvideo -pixel_format rgb48le -video_size 1920x1080 -i - out.tiff