Randomness Introduced in Gnuradio WAV Source Block?

on 2013-01-15 07:49

Dear Gnuradio,

  I wrote a program that uses a WAV source block. I found that my 
program ran as expected on my CENTOS and UBUNTU machines (producing the 
same output for a given input), but I noticed something unusual on my 
Gentoo machine. If I run the decoder against the same input WAV file, I 
get different output every time! My program is an APT decoder, so the 
resulting output is an image. The images look similar, but they have 
different intensities. (some are darker, some lighter)

  I eventually determined, that the randomness was added somewhere in 
the WAV Source block. Has anyone seen this?

This little program shows where the problem may be. The input is a WAV 
file. The float stream is converted to chars, and then dumped to a file. 
This should be completely reproducible, but it doesn't seem to be in the 
case of my Gentoo machine.

-----------------
class top_block(gr.top_block):

        def __init__(self):
                gr.top_block.__init__(self, "WAV TEST")

                inputFileName = str(sys.argv[1])
                outputFileName = str(sys.argv[2])

                self.gr_wavfile_source_0 = 
gr.wavfile_source(inputFileName, False)
                self.gr_float_to_uchar_0 = gr.float_to_uchar()
                self.gr_file_sink_0 = gr.file_sink(gr.sizeof_char*1, 
outputFileName)
                self.gr_file_sink_0.set_unbuffered(False)

                self.connect((self.gr_wavfile_source_0,0), 
(self.gr_float_to_uchar_0, 0))
                self.connect((self.gr_float_to_uchar_0, 0), 
(self.gr_file_sink_0, 0))

if __name__ == '__main__':

        tb = top_block()
        tb.run(True)
-----------------
I used the same WAV file input 4 times, and got 4 different outputs.

This is the same problem-computer that gives me the make test errors, so 
that may be related.

                   Sincerely,
          Tommy James Tracy II
            PhD Student
High Performance Low Power Lab
           University of Virginia

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