[Tex/LaTex] Positioning labels on edges of tikz-qtree

Question

I'm making a tree in a document with tikz-qtree and I managed to make the tree.
I've also added labels to the edges, without any problems.
However, the labels appear at the top of the edge, i.e. a lot closer to the parent node than the child node. I'd like to have the labels in the middle. How can I accomplish that?

I checked out this question on positioning labels, but i can't figure out from the answer what it actually is they did…

My code is as followed:

\begin{tikzpicture}[every tree node/.style={draw,circle},
   level distance=1.25cm,sibling distance=1cm,
   edge from parent path={(\tikzparentnode) -- (\tikzchildnode)}]
\Tree
[.a
    \edge node[auto=right] {$[a]$};
    [.b 
       \edge node[auto=right] {$[b]$};
       [.1 ]
       \edge node[auto=left] {$[b]$};
       [.2 ]
        ]
    \edge node[auto=left] {$[a]$};
    [.c 
        \edge node[auto=right] {$[c]$};
        [.3 ]
        \edge node[auto=left] {$[c]$};
        [.4 ]
        ]
]
\end{tikzpicture}

As provided in the answer, here the actual solution that I used (Note that Christian R.'s solution also works:

\begin{tikzpicture}[every tree node/.style={draw,circle},
   level distance=1.25cm,sibling distance=1cm,
   edge from parent path={(\tikzparentnode) -- (\tikzchildnode)}]
\Tree
[.a
    \edge node[auto=right,pos=.6] {$[a]$};
    [.b 
       \edge node[auto=right,pos=.8] {$[b]$};
       [.1 ]
       \edge node[auto=left,pos=.8] {$[b]$};
       [.2 ]
        ]
    \edge node[auto=left,pos=.6] {$[a]$};
    [.c 
        \edge node[auto=right,pos=.8] {$[c]$};
        [.3 ]
        \edge node[auto=left,pos=.8] {$[c]$};
        [.4 ]
        ]
]
\end{tikzpicture}

Giving as result:

Answer 1

You could use the option midway, like so:

\edge node[midway,left] {$[b]$};

Code

\documentclass{article}
\usepackage{tikz}
\usepackage{tikz-qtree}
\begin{document}
\begin{tikzpicture}[every tree node/.style={draw,circle},
   level distance=1.25cm,sibling distance=1cm,
   edge from parent path={(\tikzparentnode) -- (\tikzchildnode)}]
\Tree
[.a
    \edge node[auto=right] {$[a]$};
    [.b 
       \edge node[midway,left] {$[b]$};
       [.1 ]
       \edge node[midway,right] {$[b]$};
       [.2 ]
        ]
    \edge node[auto=left] {$[a]$};
    [.c 
        \edge node[midway,left] {$[c]$};
        [.3 ]
        \edge node[midway,right] {$[c]$};
        [.4 ]
        ]
]
\end{tikzpicture}
\end{document}

Result