sample.py 文件源码

def fadein(self, seconds, start_volume=0.0):
        """Fade the start of the sample in from the starting volume (usually zero) in the given time."""
        assert not self.__locked
        seconds = min(seconds, self.duration)
        i = self.frame_idx(seconds)
        begin = self.__frames[:i]  # we fade this chunk
        end = self.__frames[i:]
        numsamples = len(begin)/self.__samplewidth
        increase = 1.0-start_volume
        _sw = self.__samplewidth     # optimization
        _getsample = audioop.getsample   # optimization
        _incr = increase/numsamples    # optimization
        faded = Sample.get_array(_sw, [int(_getsample(begin, _sw, i)*(i*_incr+start_volume)) for i in range(int(numsamples))])
        begin = faded.tobytes()
        if sys.byteorder == "big":
            begin = audioop.byteswap(begin, self.__samplewidth)
        self.__frames = begin + end
        return self