Beamer: count included PDF for frame numbering

Question

For adding an existing PDF to a beamer document, it was explained to use \includepdf with the following code:

\documentclass{beamer}
\usepackage{pdfpages}
\usetheme{Montpellier}
\addtobeamertemplate{navigation symbols}{}{%
    \usebeamerfont{footline}%
    \usebeamercolor[fg]{footline}%
    \hspace{0.5cm}%
    \raisebox{1.5pt}{\insertframenumber/\inserttotalframenumber}
}
\begin{document}
{
\setbeamercolor{background canvas}{bg=}
\includepdf{filea.pdf}
}
\end{document}

This way, however, no frame is created and thus, the page (or frame) isn't counted for the numbering in the bottom right (I have two pages 0/20). Since this defies the purpose of numbering at a presentation, I'd like to change this.

Answer 1

You can manually increase the framenumber counter to take the included pdf into account:

\documentclass{beamer}
\usepackage{pdfpages}
\usetheme{Montpellier}
\addtobeamertemplate{navigation symbols}{}{%
    \usebeamerfont{footline}%
    \usebeamercolor[fg]{footline}%
    \hspace{0.5cm}%
    \raisebox{1.5pt}{\insertframenumber/\inserttotalframenumber}
}
\begin{document}

\begin{frame}
content...
\end{frame}

{
\addtocounter{framenumber}{1}
\setbeamercolor{background canvas}{bg=}
\includepdf{example-image-a4-numbered}
}

\begin{frame}
content...
\end{frame}

\end{document}