！包 inputenc 错误：使用的键盘字符未定义

Question

我是 Latex 的新手，尤其是 Beamer，我正在用法语做我的论文报告，这些字母总是让我很难受，因为昨天当我编译标题时出现错误，我用 utf8x 替换了 utf8，仍然没有变化，我添加了这个

\usepackage{newunicodechar} 
\DeclareUnicodeCharacter{FFFD}{?????}

命令，我在本论坛中读到一个问题，以揭示导致此错误的字母，但在我的情况下不起作用，这里是下面的代码，请帮我解决这个问题，谢谢。

\documentclass[12pt]{beamer}
\usetheme{Singapore}
\usepackage[utf8]{inputenc}
\usepackage[french]{babel}
\usepackage[T1]{fontenc}
\usepackage{amsmath}
\usepackage{amsfonts}
\usepackage{amssymb}
\usepackage{graphicx}
\usepackage{appendixnumberbeamer} 

%-------------------------------------------------------------------------------
%Footer section
%-------------------------------------------------------------------------------

\setbeamercolor{footlinerule}{use=structure,bg=structure.fg!25!bg}

\setbeamertemplate{footline}
{%
  \begin{beamercolorbox}[wd=\paperwidth,ht=0.5ex,dp=0ex,center]{footlinerule}
  \end{beamercolorbox}%
  \begin{beamercolorbox}[wd=\paperwidth,ht=0.6ex,dp=0ex,center]{empty}
  \end{beamercolorbox}%
  \leavevmode%
  \hbox{%
  \begin{beamercolorbox}[wd=.333333\paperwidth,ht=2.25ex,dp=2ex,center]{author in head/foot}%
    \usebeamerfont{author in
head/foot}%
  \insertshortauthor\hspace{1em}(\insertshortinstitute)
  \end{beamercolorbox}%
  \begin{beamercolorbox}[wd=.333333\paperwidth,ht=2.25ex,dp=2ex,center]{title in head/foot}%
    \usebeamerfont{title in head/foot}\insertshorttitle
  \end{beamercolorbox}%
  \begin{beamercolorbox}[wd=.333333\paperwidth,ht=2.25ex,dp=2ex,right]{date in head/foot}%

    \insertframenumber{} / \inserttotalframenumber\hspace*{2ex} 
  \end{beamercolorbox}}%
  \vskip0pt%
}%

%-------------------------------------------------------------------------------
%Report title
%-------------------------------------------------------------------------------
\author{Me}
\title{application web pour gestion des filtres}
%\setbeamercovered{transparent} 
\setbeamertemplate{navigation symbols}{} 
\logo{\includegraphics[scale=0.2]{logo.png}} 
\institute[ESSECT]{ESSECT} 
\date{18 mai 2015} 
\subtitle{Rapport du projet fin d’étude}


%-------------------------------------------------------------------------------
%sommaire automatique
%-------------------------------------------------------------------------------
\setbeamerfont{myTOC}{series=\bfseries,size=\Large}
\AtBeginSection[]
{
  \begin{frame}
  \frametitle{Sommaire}
  \tableofcontents[currentsection, hideothersubsections, pausesubsections]
  \end{frame} 
}

\begin{document}

\begin{frame}[plain,noframenumbering]
\titlepage
\end{frame}

\begin{frame}[allowframebreaks]

\frametitle{Table des matières}
\tableofcontents[pausesections]

\end{frame}

\begin{frame}[allowframebreaks]

\frametitle{Cadre du projet et l'étude de l'éxistant}
\section[]{Cadre du projet et l'étude de l'existant}
\subsection{Introduction}
Dans ce niveau on va comprendre le domaine ou le metier de l'entreprise et des personnes qui y travaillent pour mieux satisfaire leurs besoins. Il s'agit aussi de construire
l'organigramme de l'organisation l'étudiée.

\end{frame}

\begin{frame}[allowframebreaks]
\subsection{Cadre du stage}
\end{frame}

\begin{frame}[allowframebreaks]
\subsubsection{Environnement du stage}
\end{frame}

\begin{frame}[allowframebreaks]
\subsubsection{Historique}
\subsubsection{Principales missions}
\end{frame}

\begin{frame}[allowframebreaks]
\subsection{L'organigramme}
\end{frame}

\begin{frame}[allowframebreaks]
\subsection{Étude de l'éxistant}
\end{frame}

\begin{frame}[allowframebreaks]
\subsubsection{Déscription}

\subsubsection{Analyse de l'éxistant}
\end{frame}

\begin{frame}[allowframebreaks]
\subsubsection{Problématiques}
\end{frame}

\begin{frame}[allowframebreaks]
\subsubsection{Solution envisagée}
\end{frame}

\begin{frame}[allowframebreaks]
\subsection{Méthodologie de developpement et conception}
\end{frame}

\begin{frame}[allowframebreaks]
\subsubsection{Modèle de conception}
\end{frame}

\begin{frame}[allowframebreaks]
\subsubsection{Langage UML}
\end{frame}

\begin{frame}[allowframebreaks]
\subsubsection{Approche en Cascade}
\end{frame}

\begin{frame}
\subsection{Conclusion}
\end{frame}

\begin{frame}[allowframebreaks]
\section{Capture des besoins}
\end{frame}

%-----------------------------------------------------------------------------------------
%Extra slides that won't effect my page numbering
%-----------------------------------------------------------------------------------------

\appendix 
\begin{frame}{First Extra slide}
...
\end{frame}

\begin{frame}[allowframebreaks]{References}
\def\newblock{}
\bibliographystyle{plain}
\bibliography{mybib}
\end{frame}

\end{document}