'Read bit rate in bit/sec. Returns None on error.'

def getBitRate(self):

    layer = (3 - self['layer'].value)
    bit_rate = self['bit_rate'].value
    if (bit_rate in (0, 15)):
        return None
    if (self['version'].value == 3):
        dataset = self.BIT_RATES[1]
    else:
        dataset = self.BIT_RATES[2]
    try:
        return (dataset[layer][bit_rate] * 1000)
    except (KeyError, IndexError):
        return None
