Creating and editing media with FLOSS isn't that hard as it used to be in the past. There has been a lot of work to optimize the linux kernel for real-time operation allowing low latency audio processing. Today hardware drivers (e.g. for graphics cards) are already included or provided as modules by its vendors and there is plenty of audio and video software available.
I'll describe how to setup a media studio with GNU/Linux by documenting my installation. This guide may contain configuration details specific to Arch Linux, which I'm using, but should be adaptable to other distributions. There are packages and distributions as OS pre-configured for low latency and providing various applications for audio and video like:
to name a few. And I'd recommend to start with one of these projects, especially if you're new to GNU/Linux and FLOSS. But for advanced tweaking and full flexibility, you should start building a custom environment as explained in the articles above to fit your needs.