Returns a view into a channel of samples.

    samples    : a numpy array representing the audio data
    ch         : the channel to extract (channels begin with 0)

def getchannel(samples: np.ndarray, ch:int) -> np.ndarray:
    """
    Returns a view into a channel of samples.

    samples    : a numpy array representing the audio data
    ch         : the channel to extract (channels begin with 0)
    """
    N = numchannels(samples)
    if ch > (N - 1):
        raise ValueError("channel %d out of range" % ch)
    if N == 1:
        return samples
    return samples[:, ch]