You are an expert in writing code in many different languages. Your goal is to perform code completion for the following code, keeping in mind the rest of the code and the file meta data.
    Metadata details:
    filename: denoise_filter.m
    path of file: ./repos/fieldtrip/external/dss
    
    the code of the file until where you have to start completion: function [params, s_new] = denoise_filter(params, s, state)

    
function [params, s_new] = denoise_filter(params, s, state)
% Generic filter function. Can be used as DSS denoising function.
%   [params, s_new] = denoise_filter(params, s, state)
%     params  Defines the used filter
%       params.filter_conv  Inpulse response for convolution filter
%       params.filter_dct   Mask for DCT filter
%       params.filter_fft   Mask for FFT filter
%       none of above       Pass the signal unfiltered
%     state   DSS algorithm state (not used)
%     s       Source signal, matrix of row vector signals
%     s_new   Filtered signal

% Copyright (C) 2004, 2005 DSS MATLAB package team (dss@cis.hut.fi).
% Distributed by Laboratory of Computer and Information Science,
% Helsinki University of Technology. http://www.cis.hut.fi/projects/dss/.
% $Id$

if nargin<3
    params.name = 'Generic filter';
    params.description = 'Generic filter function for convolutive, DCT and FFT filtering';
    params.param = {'filter_conv', 'filter_dct', 'filter_fft'};
    params.param_value ={[], [], []};
    params.param_type = {'vector', 'vector', 'vector'};
    params.param_desc = {'Convolution coefficients', 'DCT filter coefficients', 'FFT filter coefficients.'};
    params.approach = {'pca', 'defl', 'symm'};
    params.beta = {'beta_global'};
    return;
end