Detect beat-per-minute of current stream.
BPM value. If algorithm can't detect BPM value, return value is 0.
This function will scan current stream and detect beat-per-minute.
Detection process can take some time.
BPM detection algorithm isn't 100 % accurate. Algorithm will stop when first valid BPM value is detected. If BPM value can't be detected, algorithm will try to search whole stream. If this fails, returned BPM value is 0.