Have a look at eos-movrec-code: sourceforge.net/projects/eos-movrec/ .

You have to compile it on the raspi, just follow the folllowing actions in the linux terminal:

Before all you have to install with apt some prerequisites

$ sudo apt-get update
$ sudo apt-get install subversion cmake qt5-default libgphoto2-dev

get the code:

$ svn checkout svn.code.sf.net/p/eos-movrec/code/trunk eos-movrec-code

compile the code
$ cd eos-movrec-code
$ mkdir build
$ cd build
$ cmake -DCMAKE_BUILD_TYPE=Release ..
$ make

When everything went fine, you find the executable `eos_movrec` in this directory.

It worked fine for me (Canon EOS 450d)