render-yt () 
{ 
    if [[ $# != 1 ]]; then
        echo "specify file to render";
        return;
    fi;
    _render-size "$1" 320 240
}

_render-size is a function
_render-size () 
{ 
    if [[ $# != 3 ]]; then
        echo "specify file to render, width and height";
        return;
    fi;
    file="$1";
    if [[ "${file%.sif*}" == "$file" ]]; then
        file="$1.sifz";
    fi;
    cd "$(dirname "$file")";
    synfig="synfig";
    cmd="$synfig -w $2 -h $3 -t png \"$file\"";
    echo $cmd;
    eval "$cmd" && mencoder "mf://${file%.sif*}????.png" -mf fps=24 -o "${file%.sif*}.avi" -ovc lavc -lavcopts vcodec=mjpeg
}