:returns: The detected sound channel
        :rtype: string

def _get_channel(self):
        """
        :returns: The detected sound channel
        :rtype: string
        """
        if self.channel is None:
            # Get default channel as the first one that pops up in
            # 'amixer scontrols' output, which contains strings in the
            # following format:
            #
            #     Simple mixer control 'Master',0
            #     Simple mixer control 'Capture',0
            out = check_output(['amixer', 'scontrols']).decode()
            m = re.search(r"'(?P<channel>[^']+)'", out)
            if m:
                self.channel = m.group('channel')
            else:
                self.channel = 'Playback'

        return self.channel