FFmpegSource (usually known as FFMS or FFMS2) is a cross-platform
wrapper library around FFmpeg. It gives you an easy, convenient
way to say "open and decompress this media file for me, I don't
care how you do it" and get frame- and sample-accurate access
(usually), without having to bother with the sometimes less than
straightforward and less than perfectly documented FFmpeg API.

The library is written in C++, but the public API is pure C, so if
you can link to a C library, you can use FFMS2.