Change title page template in beamer

Question

I would like to change the title page in beamer. Thus I tried to change it with defbeamertemplate as you can see above :

\documentclass{beamer}
\title{A title}
\date{\today}
\institute{home}
\author{me}
\defbeamertemplate*{title page}{default}[1][]
{
}

\begin{document}

\begin{frame}
    \titlepage
\end{frame}

\begin{frame}
    \frametitle{plop}
    plop

    plop
\end{frame}
\end{document}

My problem is that even with a simple example such as above, I got the following error message :

! LaTeX Error: Command \beamer@@tmpop@title page@default already defined.
               Or name \end... illegal, see p.192 of the manual.

actually the page 192 of the manual does not help me so much ...

Answer 1

With

\defbeamertemplate{<element>}{<option>} 

you install an <option> for the template called <element>; once this has been done, the defined template can be used with

\setbeamertemplate{<element>}[<option>]

In your case you get an error message since the default option for the title page template is already defined. You can use

\defbeamertemplate{title page}{<name>}
{
<some actions>
}

(the syntax for \defbeamertemplate is more complex, but this is not relevant here), if the option has not been previously defined for the template, and then use

\setbeamertemplate{title page}[<name>]

but since this is a local modification (intended to be used in a document and not, for example, in the design of a new theme), it's simpler to just use

\setbeamertemplate{title page}
{
<some actions>
}