add README documentation

README.md

@@ -1,5 +1,63 @@
 # ffmpego
 
-**ffmpego** is a Go wrapper around the `ffmpeg` command for reading and writing videos. It can be used to programmatically manipulate media in a simple way.
+**ffmpego** is a Go wrapper around the `ffmpeg` command for reading and writing videos. It can be used to programmatically manipulate media with a simple, friendly interface.
 
+# Usage
+
+## Writing a video
+
+To encode a video, create a `VideoWriter` and write `image.Image`s to it. Here's the simplest possible example of encoding a video:
+
+```go
+fps := 24.0
+width := 50
+height := 50
+
+vw, _ := ffmpego.NewVideoWriter("output.mp4", width, height, fps)
+
+for i := 0; i < 24; i++ {
+    // Create your image.
+    frame := image.NewGray(image.Rect(0, 0, width, height))
+
+    vw.WriteFrame(frame)
+}
+
+vw.Close()
+```
+
+## Reading a video
+
+Decoding a video is similarly straightforward. Simply create a `VideoReader` and read `image.Image`s from it:
+
+```go
+vr, _ := NewVideoReader("input.mp4")
+
+for {
+    frame, err := reader.ReadFrame()
+    if err == io.EOF {
+        break
+    }
+    // Do something with `frame` here...
+}
+
+vr.Close()
+```
+
+# Installation
+
+This project depends on the `ffmpeg` command. If you have `ffmpeg` installed, **ffmpego** should already work out of the box.
+
+If you do not already have ffmpeg, you can typically install it using your OS's package manager.
+
+Ubuntu:
+
+```
+$ apt install ffmpeg
+```
+
+macOS:
+
+```
+$ brew install ffmpeg
+```