RTLSDR baseband file format

I am trying out the RTLSDR FM demodulator code for MATLAB as presented here:  https://www.mathworks.com/help/supportpkg/rtlsdrradio/examples/fm-broadcast-receiver.html

Playing FM radio in near real-time directly from my RTLSDR works great! What I can't figure out is how to make it work with a data file. When I select the data file option, it asks

Enter captured signal file name [rbds_capture.bb]

But I have some pre-recorded .dat files from my RTL-SDR, but they don't seem to be compatible with the file reader. When I try to read a .dat file, I get this error:

\Error using coder.internal.errorIf (line 8)
Invalid baseband file: Incorrect file version..

What format is it expecting? Is there a way to convert a raw data file to a baseband file?

[Ethem]

How did you create the .dat file? If you can read that file in MATLAB, you can write the contents to a .bb file. An example psuedo-code is:

x = read_my_dat_file('myfile.dat')

bbw = comm.BasebandFileWriter('myfile_in_bb')

bbw(x)