From Gnash Project Wiki
SDL, or Simple Direct Media Layer, is a cross-platform multimedia free software library that creates an abstraction over various platforms' graphics, sound, and input APIs.
- Gnash can use SDL as a GUI and/or as a sound handler. Note that the two usages are independent of each other: you can use it for a task and not for the other if you wish.
- As of 2007-01-11 the SDL GUI lacks menus and a performant input event architecture; the SDL sound handler is the most feature rich, supporting Video through FFmpeg.
- The SDL-sound handler uses ffmpeg or libmad for decoding mp3-audio, though it can be built without mp3-support.
- It is recommended to use the SDL sound handler since it is more feature complete.