TDMS save as WAV file, not always working

[sjgsjgsjg5509]

I have some waveforms saved in .tdms files.  I want to convert them to .wav audio files.  In DIAdem, I'd did 'Save As' then chose 'Audio .wav'. When I open the .wav file up in an audio player/editor, it is silent; it's just an empty line.

Now, my original .tdms waveform data goes from ~[-2,2]. When I scale the waveform in DIAdem down to ~.30, the .wav file then behaves properly.  Is there a different way for me to avoid this issue?  Is this due to some sort of specifications of the .wav file format?  I attached some pictures.

[sjgsjgsjg5509]

Note: I think what I am doing is part of the Audio Dataplugin

[Brad_Turpin · Accepted solution]

Hi sj,

You either have to scale the waveform channels to the I32 data values yourself or happen to be in a valid scaling range for the WAV file format.  I find the former approach easier to remember:

Volume = 0.5 ' 0.0 - 1.0
FOR Each Channel In Data.GetChannels("*")
  Amplitude = MaxV(Abs(CMin(Channel)), CMax(Channel))
  Call ChnLinScale(Channel, Channel, Volume*2^31/Amplitude, 0)
  Call ChnCharacter(Channel)
NEXT
Call DataFileSave(WavFilePath, "Audio")

Brad Turpin

DIAdem Product Support Engineer

National Instrument