In this post I will show you how to decode APRS frames using Sound Modem by UZ7H0. You should use the low speed sound modem (Version 0.97b on 14/10/2017).
You need an audio [Download 260 Mb] file with APRS information, here you have one from the WA8LMF TNC Test CD Download
To send audio from the audio file to the SoundModem, you have to install Virual Audio Cable.
Now play the audio file to de Virtual Sound Cable Device.
Start Audio player like VLC .
And open SoundModem->Settings->Devices and select AFSK AX.25 1200 bd and decoding process will start.
Thanks to all the students and Ham Radio that produce this knowledge in GranaSAT team.