sample.py 文件源码

def __db_level(self, rms_mode=False):
        """
        Returns the average audio volume level measured in dB (range -60 db to 0 db)
        If the sample is stereo, you get back a tuple: (left_level, right_level)
        If the sample is mono, you still get a tuple but both values will be the same.
        This method is probably only useful if processed on very short sample fragments in sequence,
        so the db levels could be used to show a level meter for the duration of the sample.
        """
        maxvalue = 2**(8*self.__samplewidth-1)
        if self.nchannels == 1:
            if rms_mode:
                peak_left = peak_right = (audioop.rms(self.__frames, self.__samplewidth)+1)/maxvalue
            else:
                peak_left = peak_right = (audioop.max(self.__frames, self.__samplewidth)+1)/maxvalue
        else:
            left_frames = audioop.tomono(self.__frames, self.__samplewidth, 1, 0)
            right_frames = audioop.tomono(self.__frames, self.__samplewidth, 0, 1)
            if rms_mode:
                peak_left = (audioop.rms(left_frames, self.__samplewidth)+1)/maxvalue
                peak_right = (audioop.rms(right_frames, self.__samplewidth)+1)/maxvalue
            else:
                peak_left = (audioop.max(left_frames, self.__samplewidth)+1)/maxvalue
                peak_right = (audioop.max(right_frames, self.__samplewidth)+1)/maxvalue
        # cut off at the bottom at -60 instead of all the way down to -infinity
        return max(20.0*math.log(peak_left, 10), -60.0), max(20.0*math.log(peak_right, 10), -60.0)