Shifting data when reading from binary file using fread

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Lars Janssen
Lars Janssen 2019-5-29
评论： Lars Janssen 2019-5-30
I am trying to read experimental data from a binary file using fread. While the resulting data is read almost correct, the data is slightly shifting in a seemingly unpredictable manner. An example of this is given below (note that the direction of shifting is different for all signals):
fig1.png
While the result should look more like:
fig2.png
I am using the following code:
fid = fopen('sound_s3');
data = fread(fid,[1024, inf],'int32'); % reading in the 1024 signals of ~50k samples each
fclose(fid);
data = data/2^31; % converting bit to pressure
% plotting the examples
figure
plot(data(1,1:20000)');
xlabel('sample');ylabel('pressure')
figure
data = data - smoothdata(data,2,'movmean',1000);
plot(data(1,1:20000)');
xlabel('sample');ylabel('pressure')
Does anyone know what could cause this issue? I have tried basically all 'fread' options, and I am sure that the data is stored in 32 bit precision.
Note that I am sure that the signal is measured and should look like the second image.
Thanks in advance!
  11 个评论
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Walter Roberson
Walter Roberson 2019-5-30
I got lost in the question of bit depth. One part says that the daq are single bit and then a second later it was talking about 32 bits per sample.
Lars Janssen
Lars Janssen 2019-5-30
Thanks for the help anyways! I will try to look if I can further reverse engineer the files. If I find anything I will let you know.

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