frequency_estimator.py 文件源码

def freq_from_autocorr(sig, fs):
    """
    Estimate frequency using autocorrelation
    """
    # Calculate autocorrelation (same thing as convolution, but with
    # one input reversed in time), and throw away the negative lags
    corr = fftconvolve(sig, sig[::-1], mode='full')
    corr = corr[len(corr)//2:]

    # Find the first low point
    d = diff(corr)
    start = find(d > 0)[0]

    # Find the next peak after the low point (other than 0 lag).  This bit is
    # not reliable for long signals, due to the desired peak occurring between
    # samples, and other peaks appearing higher.
    # Should use a weighting function to de-emphasize the peaks at longer lags.
    peak = argmax(corr[start:]) + start
    px, py = parabolic(corr, peak)

    return fs / px