The Raspberry Pi is a fantastic little computer for recording video. For about €50,- you can record in HD with full customizability and for as long as you want or have storage for. However, one issue is that the .h264 container it records in is hard to work with. It is therefore often important to convert videos to widely applicable formats like .mp4 to be able to view them properly and get the right meta information. For this I recommend the program FFmpeg.
Installing ffmpeg on a Raspberry Pi is not as simple as downloading an executable from the command line, but it is also not too difficult.
sudo apt-get install libmp3lame-dev git clone --depth 1 https://code.videolan.org/videolan/x264 cd x264 ./configure --host=arm-unknown-linux-gnueabi --enable-static --disable-opencl make -j4 sudo make install
git clone git://source.ffmpeg.org/ffmpeg --depth=1 cd ffmpeg ./configure --arch=armel --target-os=linux --enable-gpl --enable-libx264 --enable-nonfree --enable-libmp3lame make -j4 sudo make install
Now you are ready to convert a h264 video on your Raspberry Pi! Simply run the following command:
ffmpeg -i USER_VIDEO.h264 -vcodec copy USER_VIDEO.mp4
There are many options available and many other ways to convert h264 videos with ffmpeg, but this command is the quickest of all methods that I tested as it basically just changes the container without re-encoding.