Question about the smoothness metric

[AnjieCheng]

Hi, thanks for sharing this awesome work!

I'm interested in the smoothness metric mentioned in your CVPR'19 paper. If you don't mind, could you share the implementation details or short code snippets for Eq. 9?

Thank you!

[gabrieleilertsen]

Hi. This is a Matlab-implementation of the smoothness metric:

function S = video_smoothness( test_vid, ref_vid, fps )
  if nargin < 3
      fps = 30;
  end

  freq_cutoff = 0.15; % [s] - this should remove less visible temporal frequencies
  sigma = fps*freq_cutoff;

  test_hp = get_hp(test_vid);
  ref_hp = get_hp(ref_vid);

  S = mean( ref_hp(:) ) / mean( test_hp(:) );

  function vid_hp = get_hp( vid )        

      k_size = round(ceil( sigma*5 )/2)*2;
      xx = linspace( -k_size/2, k_size/2, k_size+1 );
      gauss_kernel = exp( -xx.^2 / (2*sigma^2) );
      gauss_kernel = gauss_kernel/sum(gauss_kernel);

      vid_lp = filtfilt( gauss_kernel, 1, vid );

      vid_hp = sqrt(mean((vid - vid_lp).^2,1));

  end
end

[AnjieCheng]

Thank you! That helps a lot.