Update codec to be dynamically registered

pkg/codec/codec.go

@@ -11,3 +11,12 @@ type VideoDecoder interface {
 	Decode([]byte) (image.Image, error)
 	Close() error
 }
+
+type VideoSetting struct {
+	Width, Height             int
+	TargetBitRate, MaxBitRate int
+	FrameRate                 float32
+}
+
+type VideoEncoderBuilder func(s VideoSetting) (VideoEncoder, error)
+type VideoDecoderBuilder func(s VideoSetting) (VideoDecoder, error)