Increasing the height of the Beamer footline

Question

When I add a tabularenvironment to the footline of my presentation, only the first line is shown. How can I increase the heigth of the footline to show the whole table?

\documentclass[12pt,ngerman]{beamer}
\usepackage[utf8]{inputenc}
\usepackage[T1]{fontenc}
\setbeamertemplate{navigation symbols}{}

\begin{document}

\setbeamertemplate{footline}{
{
\tiny\begin{tabular}{p{0.25\textwidth}p{0.25\textwidth}p{0.45\textwidth}}
First line & John Doe & fsdfs\\ 
second line \& Title of the talk & dsdfsd\\
some third line & & 
\end{tabular}
}}

\frame{
\frametitle{fdfsdgdf}

\begin{itemize}
\item 
\item 
\item 
\end{itemize}
}

\end{document}

Answer 1

One option would be to patch the \beamer@calculateheadfoot command (defined in the file beamerbaseframecomponents.sty) to add some space for the new footline:

\documentclass[12pt,ngerman]{beamer}
\usepackage[utf8]{inputenc}
\usepackage[T1]{fontenc}
\usepackage{etoolbox}
\usepackage{lipsum}

\setbeamertemplate{navigation symbols}{}

\makeatletter
\patchcmd{\beamer@calculateheadfoot}{\advance\footheight by 4pt}{\advance\footheight by 20pt}{}{}
\makeatother

\setbeamertemplate{footline}{
{%
\begin{beamercolorbox}[wd=\paperwidth,ht=1.5ex,dp=20pt,leftskip=.3cm,rightskip=.3cm]{author in head/foot}
\tiny\begin{tabular}[t]{@{}p{0.25\textwidth}p{0.25\textwidth}p{0.38\textwidth}@{}}
First line & John Doe & fsdfs\\ 
second line \& Title of the talk & dsdfsd\\
some third line & & 
\end{tabular}
\end{beamercolorbox}
}}

\begin{document}

\frame{
\frametitle{Test Frame}
\lipsum[4]
}

\end{document}

I also added a beamercolorbox to the definition, but this is completely optional.

Answer 2

With the current beamer development version (should be included in beamer v3.70 or newer), beamer now recalculates the head- and footheight at the start of each frame, so you can use your code as it is:

\documentclass[12pt,ngerman]{beamer}
\usepackage[utf8]{inputenc}
\usepackage[T1]{fontenc}
\setbeamertemplate{navigation symbols}{}
\begin{document}
\setbeamertemplate{footline}{
{
\tiny\begin{tabular}{p{0.25\textwidth}p{0.25\textwidth}p{0.45\textwidth}}
First line & John Doe & fsdfs\ 
second line & Title of the talk & dsdfsd\
some third line & & 
\end{tabular}
}}
\frame{
\frametitle{fdfsdgdf}
\begin{itemize}
\item 
\item 
\item 
\end{itemize}
}
\end{document}