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Re: Possible bug in WAV export

  • To: mathgroup at smc.vnet.net
  • Subject: [mg87930] Re: Possible bug in WAV export
  • From: Szabolcs Horvát <szhorvat at gmail.com>
  • Date: Sat, 19 Apr 2008 23:55:03 -0400 (EDT)
  • Organization: University of Bergen
  • References: <ftsd0o$ba7$1@smc.vnet.net> <ftv8on$7kv$1@smc.vnet.net> <fu9fuh$cen$1@smc.vnet.net>

m.r at inbox.ru wrote:
>> To demonstrate that this unbelievable thing really happens, here's an
>> another example, together with the result.  Note that the very same
>> command returns different results in subsequent evaluations:
>>
>> In[1]:=
>> Table[
>>  Total[#[[1, 1, 1]]] &@
>>   ImportString[
>>    ExportString[
>>     Play[Sum[Sin[2 Pi 440 k t], {k, 1, 4}], {t, 0, 1},
>>      SampleRate -> 44100, SampleDepth -> 16], "WAV"], "WAV"],
>>  {20}]
>>
>> Out[1]= {0., 268.745, -0.752563, -0.756226, -0.756226, -2.99866, 0., \
>> 0., -2.98279, 0., 0.756226, 341.993, 0., -0.752563, 0., 268.017, \
>> -0.752563, 0., -2.2522, 0.}
>>
>> The small fluctuations could be explained by dithering, but any
>> reasonably precise result cannot have a sum of 342!  The sound
>> function was constructed in such a way that the sum should be 0.
> 
> A workaround is to use PlayRange -> All.
> 

Thank you, this works well!  I am still wondering about what causes the 
randomness, though.  With PlayRange -> All, the sums are always 0., so 
it cannot be dithering.


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