Hi are you using dsp.DyadicAnalysisFilterBank? In that case the input signal must be a multiple of four along its first dimension. If you have the Wavelet Toolbox, then you can use wavedec() inside of a MATLAB function block. wavedec() is supported for code generation. That will work on an arbitrary length input signal length, however, you can't expect the wavelet and scaling coefficients to be the same length if the input signal is changing length.