Detect beat and play (wav) file in a synchronised manner

Question

I am trying my hands at Audio Processing in python with this Beat Detection algorithm. I have implemented the first (non-optimized version) from the aforementioned article.

Answer 1

Working beat detection code (NumPy / PyAudio)

If you are using NumPy this code might help. It assumes the signal (read with PyAudio) is 16-bit wide Int. If that is not the case change or remove the signal.astype() and adjust the normalization-divider (max int16 here).

class SimpleBeatDetection:
    """
    Simple beat detection algorithm from
    http://archive.gamedev.net/archive/reference/programming/features/beatdetection/index.html
    """
    def __init__(self, history = 43):
        self.local_energy = numpy.zeros(history) # a simple ring buffer
        self.local_energy_index = 0 # the index of the oldest element

    def detect_beat(self, signal):

        samples = signal.astype(numpy.int) # make room for squares
        # optimized sum of squares, i.e faster version of (samples**2).sum()
        instant_energy = numpy.dot(samples, samples) / float(0xffffffff) # normalize

        local_energy_average = self.local_energy.mean()
        local_energy_variance = self.local_energy.var()

        beat_sensibility = (-0.0025714 * local_energy_variance) + 1.15142857
        beat = instant_energy > beat_sensibility * local_energy_average

        self.local_energy[self.local_energy_index] = instant_energy
        self.local_energy_index -= 1
        if self.local_energy_index < 0:
            self.local_energy_index = len(self.local_energy) - 1

        return beat

The PyAudio examples for wav read or mic record will give you the needed signal data. Create a NumPy array efficiently with frombuffer()

data = stream.read(CHUNK)
signal = numpy.frombuffer(data, numpy.int16)