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at April 8, 2011 16:32 by runnig
Initial Code
import array
import sys
import os
import math
import re
if __name__ == '__main__':
if len(sys.argv) < 3:
print "usage: %s filename1.yuv filename2.yuv [width height]" % sys.argv[0]
filename1 = sys.argv[1]
filename2 = sys.argv[2]
if filename1 == filename2:
print "warning! do you really mean to compare the file with itself?"
data1 = array.array('B')
data2 = array.array('B')
file1_size = os.path.getsize(filename1)
file2_size = os.path.getsize(filename2)
minsize = min(file1_size, file2_size)
if file1_size != file2_size:
print "warning, file sizes do not match! comparing min size %d bytes" % minsize
if len(sys.argv) >= 5:
w = int(sys.argv[3])
h = int(sys.argv[4])
else:
m = re.search(".*[_-](\d+)x(\d+).*", filename1)
assert m
w = int(m.group(1))
h = int(m.group(2))
assert w*h*3/2 <= minsize
print "(%dx%d)" %(w,h)
data1.fromfile(open(filename1,"rb"),minsize)
data2.fromfile(open(filename2,"rb"),minsize)
print "data size: %d, w*h=%d, w*h*3/2=%d" % (len(data1), w*h, w*h*3/2)
print "evaluating mse.."
def psnr(mse):
log10 = math.log10
return 10.0*log10(float(256*256)/float(mse))
def mean(seq):
if len(seq) == 0: return 0.0
else: return sum(seq)/float(len(seq))
def sum_square_err(data1, data2, beg, end):
return sum( (a-b)*(a-b) for a,b in zip(data1[beg:end],data2[beg:end]))
y = 0
u = y + (w * h)
v = u + (w/2 * h/2)
data_end = w*h*3/2
begin = [y,u,v,y]
end = [u,v,data_end,data_end]
size = [w*h, w*h/4, w*h/4, w*h*3/2]
colorspace_mse = [sum_square_err(data1,data2,
begin[i], end[i])/float(size[i]) for i in range(4)]
colorspace_psnr = [psnr(m) for m in colorspace_mse]
print "planes: Y, U, V, Whole frame"
print 'colorplane mse: ', colorspace_mse
print 'colorplane psnr: ', colorspace_psnr
Initial URL
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Evaluating PSNR metric of two YUV420 sequences in pure python
Initial Tags
python
Initial Language
Python