I started my music visualization project with a possibility to load a collection of static images, accompanied with metadata that describe their parameters like dominant colors, whether it uses alpha transparency or whether it is tileable (description of these parameters could be a topic of another blog post). I then render them as textures, moving, rotating and changing colors randomly, blended together, with a possibility of feedback from previous frame. This mathod may sometimes generate quite interesting images, but it has its own limitations and becomes boring after some time.
Generating some interesting graphics procedurally from scratch is my ultimate goal. But while writing shaders is fun and can give amazing results (as we can see on ShaderToy), it's also the hard way. So to be able to show something interesting, for now I've implemented playback of videos and animated GIFs, using FFmpeg library.
FFmpeg is a free tool that contains its own codecs for various video and audio formats (so it doesn't use the codecs installed in Windows). It is known as a command-line program that can convert about any video format, but it's also a software library that offers this encoding/decoding features to developers. I learned to use this library because I needed to implement video playback for one of my shows.
Later I discovered that it can play animated GIFs as well. This is a great feature, because having hundreds of such GIFs downloaded and being able to switch between them in an instant can make quite interesting visuals. There are many abstract, geometric, psychedelic animations shared all around the Internet, like on Op Art or Fractalgasm Facebook pages. At the same time, possibility to play all popular video formats is much more comfortable than what Resolume offers, which requires converting all the footage to its own codec, called DXDI (by the way, FFmpeg is able to play this as well).
I won't show any source code this time, but if you are a developer and consider implementing support for video playback or encoding, I recommend FFmpeg library. Other option is libVLC - a library behind popular VLC media player, which also has its own set of codecs. I also used it some time ago. Playing anmimated GIF-s is also possible through Windows Imaging Component (WIC), which is part of standard Windows API.