Cross-layer Transcoder

\begin{nskFigure}[]
	\nskBlock[id=a0, type=text, text-center={\Large Residual\\Stream}]
	\foreach \i in {1,...,3} {
			\nskBlock[id=a\i, type=circle, text-center=\textbf{+}, last-pos-s={above=3cm}]
			\nskConnect[from=\nskID{1}, to=\nskID{2}]
		}
	% marks ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ <<<
	\nskMark[id=top, last-pos={above=}]
	\nskConnect[from=\nskID{2}, to=\nskID{1}, arrow-tip={-Straight Barb}]
	% rows ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ <<<
	\foreach \i in {1,...,3} {
			\nskContainer*[id=mlp\i, pos={below right=1.5cm and 3cm of a\i}, \mlpc]{
				\nskBlock[width=.5cm, height=.5cm, text-west=\textbf{MLP~}]
				\nskBlock[width=.5cm, height=.5cm, last-pos={right=2.5mm}]
			}
			\nskContainer*[id=clt\i, last-pos={right=2.5cm}, \cltc]{
				\nskBlock[type=circle, width=.5cm, height=.5cm, text-west=\textbf{CLT~}]
				\foreach \i in {1,...,5} {
						\nskBlock[type=circle, width=.5cm, height=.5cm, last-pos={right=2.5mm}]
					}
			}
			\nskBlock[id=l\i, type=text, text-center=Layer \i, pos={left=3cm of mlp\i}]
			\nskConnect*[from=l\i, to=mlp\i, shorten-to=1mm, shorten-from=3mm, \ll]
			\nskConnect*[from=mlp\i, to=clt\i, shorten-to=1mm, shorten-from=1mm, \ll]
 
			\tikzmath{
				int \prev, int \dprev;
				\prev = \i - 1;
				\dprev = \i - 2;
			}
 
      \nskConnect*[from=a\prev, to=clt\i, bend-type=double, arrow-tip={-Straight Barb}, \al]
			\nskConnect[from=a\prev, to=mlp\i, bend-type=double]
 
			\nskConnect*[id=p\i, from=clt\i, to=a\i, bend-type=double, \al]
			\nskConnect[from=mlp\i, to=a\i, bend-type=double]
 
			% marks ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ <<<
			\nskMarkPath[at=.58]{p\i}{\nskMark[id=+\i]}
			\nskMarkPath[at=.58]{p\i}{\nskMark[id=+m\i, shift-y=-1.3mm, shift-x=-1mm]}
			\nskMarkPath[at=.25]{p\i}{\nskMark[id=c\i]}
			% marks ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ <<<
			\begin{nskSwitch}{\i}
				\nskCase[1]{}
				\nskCase[3]{
					\nskBlock*[type=circle, text-center=+, pos={left=0cm of +\i}, width=.7cm, height=.7cm, \cltc]
					\nskConnect*[from=c\prev, to=+m\i, bend-type=straight, bend-direction=left, \al]
					\nskConnect*[from=c\dprev, to=\nskID{1}.south east, bend-type=straight, bend-direction=left, \al]
				}
				\nskDefault{
					\nskBlock*[type=circle, text-center=+, pos={left=0cm of +\i}, width=.7cm, height=.7cm, \cltc]
					\nskConnect*[from=c\prev, to=\nskID{1}.south east, bend-type=straight, bend-direction=left, \al]
					\nskConnect*[from=c\prev, to=\nskID{1}.south east, bend-type=straight, bend-direction=left, \al]
				}
			\end{nskSwitch}
		}
 
\end{nskFigure}