The ffmpeg package contains ffmpeg, ffserver, libavcodec and libavformat. ffmpeg is a command line tool to convert video files, network streams, input from a TV card to several video formats. ffserver is a streaming server for everything that ffmpeg could use as input (files, streams, TV card input, webcam, etc.). libavcodec and libavformats are libraries for encoding/decoding video streams and putting them into files or network packets. Since they're well documented, you can easily include them in your software, like some other packages already do.