keytap doesn't collect training data

On FreeBSD keytap immediately goes to the "[+] Predicting" line:

$ work/.build/keytap -c3 -C2 Usage: work/.build/keytap input.kbd [input2.kbd ...] [-cN] [-pF] [-tF] -cN - select capture device N -CN - select number N of capture channels to use -pF - prediction threshold: CC > F -tF - background threshold: ampl > F*avg_background

Found 4 capture devices: - Capture device #0: '/dev/dsp' - Capture device #1: '/dev/dsp3' - Capture device #2: '/dev/dsp4' - Capture device #3: '/dev/dsp7' Attempt to open capture device 3 : '/dev/dsp7' ... Opened capture device succesfully! DeviceId: 2 Frequency: 16000 Format: 33056 (4 bytes) Channels: 2 Samples: 512 Audio Filter: 1 Cutoff frequency: 100 Hz Capturing audio .. [+] Collecting training data [+] Training Failed to train the following keys: [+] Ready to predict. Keep pressing keys and the program will guess which key was pressed based on the captured audio from the microphone. [+] Predicting

It doesn't seem to collect any training data.