Explain the following encoding code

Below code is used in encoding where B=pic(:,:,1) is matrix of image.

for v v = 1:1000  % This is the encoder.

      for uu = 1:7
          if msgmat(vv,uu)==1;
             if rem(B(idx(uu+7*(vv-1))),2)==0
                B(idx(uu+7*(vv-1))) = B(idx(uu+7*(vv-1)))+1;
             end
          elseif rem(B(idx(uu+7*(vv-1))),2)==1
                B(idx(uu+7*(vv-1))) = B(idx(uu+7*(vv-1)))-1;
          end
      end

Please tell me whats going on in above code ???? v v and uu are variables

Answer 1

[Walter Roberson]

The code sets the bottom bit of a location in B to be the same as the value of msgmat() at a location.

idx(uu+7*(vv-1)) would work out the same as idx(uu,vv) provided that idx had 7 rows.