For a command pipeline, the only output should be the - at the end. The rec command interprets the noise.wav parameter as an additional input, which will fail or produce bogus output. Try removing the extra filename (and other unnecessary/incompatible options):
rec -c 1 -t wav - | ./noise-filter > bits
2
CousinIT
per the tutorial you referenced (I'm following that one, too!) AND the latest-version SoX manpage (as of 9 Nov 2014), the complete, corrected command that worked for me was:
Entropy = 7.996356 bits per byte. Optimum compression would reduce the size of this 49152 byte file by 0 percent. Chi square distribution for 49152 samples is 247.53, and randomly would exceed this value 50.00 percent of the times. Arithmetic mean value of data bytes is 127.5771 (127.5 = random). Monte Carlo value for Pi is 3.147949219 (error 0.20 percent). Serial correlation coefficient is -0.002336 (totally uncorrelated = 0.0).
This is pretty good quality random data!
0
Alex Hofsteede
Похоже, что у вашего noise.wav нет частоты дискретизации, которую может записывать sox, и sox требует, чтобы оба файла имели одинаковую частоту дискретизации. Вам, вероятно, придется регенерировать noise.wav с более высокой частотой дискретизации.