Implements RequireKeyFrame for VPX codec (#334)

pkg/codec/vpx/vpx_test.go

@@ -20,6 +20,8 @@ func TestImageSizeChange(t *testing.T) {
 		},
 		"VP9": func() (codec.VideoEncoderBuilder, error) {
 			p, err := NewVP9Params()
+			// Disable latency to ease test and begin to receive packets for each input frame
+			p.LagInFrames = 0
 			return &p, err
 		},
 	} {
@@ -87,3 +89,72 @@ func TestImageSizeChange(t *testing.T) {
 		})
 	}
 }
+
+func TestRequestKeyFrame(t *testing.T) {
+	for name, factory := range map[string]func() (codec.VideoEncoderBuilder, error){
+		"VP8": func() (codec.VideoEncoderBuilder, error) {
+			p, err := NewVP8Params()
+			return &p, err
+		},
+		"VP9": func() (codec.VideoEncoderBuilder, error) {
+			p, err := NewVP9Params()
+			// Disable latency to ease test and begin to receive packets for each input frame
+			p.LagInFrames = 0
+			return &p, err
+		},
+	} {
+		factory := factory
+		t.Run(name, func(t *testing.T) {
+			param, err := factory()
+			if err != nil {
+				t.Fatal(err)
+			}
+
+			var initialWidth, initialHeight, width, height int = 320, 240, 320, 240
+
+			var cnt uint32
+			r, err := param.BuildVideoEncoder(
+				video.ReaderFunc(func() (image.Image, func(), error) {
+					i := atomic.AddUint32(&cnt, 1)
+					if i == 3 {
+						return nil, nil, io.EOF
+					}
+					return image.NewYCbCr(
+						image.Rect(0, 0, width, height),
+						image.YCbCrSubsampleRatio420,
+					), func() {}, nil
+				}),
+				prop.Media{
+					Video: prop.Video{
+						Width:       initialWidth,
+						Height:      initialHeight,
+						FrameRate:   1,
+						FrameFormat: frame.FormatI420,
+					},
+				},
+			)
+			if err != nil {
+				t.Fatal(err)
+			}
+			_, rel, err := r.Read()
+			if err != nil {
+				t.Fatal(err)
+			}
+			rel()
+			r.ForceKeyFrame()
+			_, rel, err = r.Read()
+			if err != nil {
+				t.Fatal(err)
+			}
+			if !r.(*encoder).isKeyFrame {
+				t.Fatal("Not a key frame")
+			}
+			rel()
+			_, _, err = r.Read()
+			if err != io.EOF {
+				t.Fatal(err)
+			}
+		})
+
+	}
+}