def computeNFrames(self):
        """
        compute Nb Frames: 
        """
        if not hasattr(self, 'totFrames'):
            if self.tfrepresentation in knownTransfos:
                # NB for hybridcqt should be the same formula,
                # but the values are a bit different in nature.
                fs, data = wav.read(self.files['inputAudioFilename'])
                self.lengthData = data.shape[0]
                self.totFrames = (
                    np.int32(np.ceil((self.lengthData - 
                                      0) / # self.stftParams['windowSizeInSamples']) /
                                     self.stftParams['hopsize']
                                     + 1) + 1)# same number as in slf.stft
                    )
                self.N = self.totFrames