Demo/sgi/video/statit.py

   1 import sys
   2 from time import millitimer
   3
   4 def main():
   5         filename = 'film2.video'
   6         if sys.argv[1:]: filename = sys.argv[1]
   7         f = open(filename, 'r')
   8
   9         line = f.readline()
  10         w, h = eval(line[:-1])
  11         w2, h2 = w/2, h/2
  12         size = w2 * h2
  13
  14         data = data2 = t = t0 = t1 = None
  15         nframes = 0
  16         t0 = millitimer()
  17         while 1:
  18                 line = f.readline()
  19                 if not line: break
  20                 t = eval(line[:-1])
  21                 data = None
  22                 data = f.read(size)
  23                 if len(data) <> size:
  24                         raise EOFError
  25                 dostat(w2, h2, data)
  26                 nframes = nframes+1
  27         t1 = millitimer()
  28
  29         t = 0.001 * (t1-t0)
  30         fps = 0.1 * int(10*nframes/t)
  31         print nframes, 'frames in', t, 'sec. =', fps, 'frames/sec.'
  32
  33 def dostat(w, h, data):
  34         print
  35         stat3(w, h, data)
  36
  37 # Statistic op 1: frequencies of byte values
  38 def stat1(w, h, data):
  39         bins = [0]*256
  40         for c in data:
  41                 i = ord(c)
  42                 bins[i] = bins[i]+1
  43         prbins(bins)
  44
  45 def prbins(bins):
  46         import string
  47         s = ''
  48         tot = 0
  49         for i in range(256):
  50                 tot = tot + bins[i]
  51                 s = s + string.rjust(`bins[i]`, 4)
  52                 if len(s) >= 4*16:
  53                         print s, string.rjust(`tot`, 7)
  54                         s = ''
  55                         tot = 0
  56
  57 # Statistic op 2: run lengths
  58 def stat2(w, h, data):
  59         runs = []
  60         for y in range(h):
  61                 count, value = 0, ord(data[y*w])
  62                 for c in data[y*w : y*w+w]:
  63                         i = ord(c)
  64                         if i <> value:
  65                                 runs.append(count, value)
  66                                 count, value = 0, i
  67                         count = count+1
  68                 runs.append(count, value)
  69         print len(runs), 'runs =', 0.1 * (10*w*h/len(runs)), 'bytes/run'
  70
  71 # Statistic op 3: frequencies of byte differences
  72 def stat3(w, h, data):
  73         bins = [0]*256
  74         prev = 0
  75         for c in data:
  76                 i = ord(c)
  77                 delta = divmod(i-prev, 256)[1]
  78                 prev = i
  79                 bins[delta] = bins[delta]+1
  80         prbins(bins)
  81
  82 # Try packing
  83 def packblock(w, h, data):
  84         res = ''
  85         for y in range(h):
  86                 res = res + packline(data[y*w : y*w+w])
  87         return res
  88
  89 def packline(line):
  90         bytes = []
  91         for c in line:
  92                 bytes.append(ord(c))
  93         prev = bytes[0]
  94         i, n = 1, len(bytes)
  95         while i < n:
  96                 for pack in (0, 2, 4, 8):
  97                         if pack == 0:
  98                                 lo, hi = 0, 0
  99                         else:
 100                                 hi = pow(2, pack-1)-1
 101                                 lo = -hi-1
 102                         p = prev
 103                         j = i
 104                         count = 0
 105                         while j < n:
 106                                 x = bytes[j]
 107                                 delta = byte(x-p)
 108                                 if not lo <= delta <= hi:
 109                                         break
 110                                 p = x
 111                                 j = j+1
 112
 113 def byte(x): return divmod(x, 256)[1]
 114
 115 main()