Boost::qi parse string

I need to parse "title" from the next hls tag

Pattern of the tag: #EXTINF:<duration>[,<title>]

For example of real tag:

#EXTINF:10,Title of the segment => I need "Title of the segment" phrase

#EXTINF:20,Title => I need "Title" phrase

#EXTINF:12 => I need "" phrase

I wrote the next code

double duration;
std::string title;

boost::spirit::qi::rule<Iterator, std::string()> quoutedString;
quoutedString %= lexeme[+(char_)];

bool r = parse(first, last,
    ("#EXTINF:" >> double_[ref(duration) = _1] >> -(',' >> quoutedString[ref(title) = _1] ) )
);
if (!r || first != last) {
    addMinorProblem(stateObj, _("Cannot parse information from #EXTINF tag"));
    return false;
}

But I got the next error in compilation process:

error: call of overloaded ‘ref(std::__cxx11::string&)’ is ambiguous
         ("#EXTINF:" >> double_[ref(duration) = _1] >> -(',' >> quoutedString[ref(title) = _1] ) )

Please help me. What am I doing wrong?