Add support snapshot for raw image format

pkg/magic/keyframe.go

@@ -24,6 +24,7 @@ func NewKeyframe() *Keyframe {
 			Direction: core.DirectionSendonly,
 			Codecs: []*core.Codec{
 				{Name: core.CodecJPEG},
+				{Name: core.CodecRAW},
 				{Name: core.CodecH264},
 				{Name: core.CodecH265},
 			},
@@ -87,6 +88,15 @@ func (k *Keyframe) AddTrack(media *core.Media, _ *core.Codec, track *core.Receiv
 		if track.Codec.IsRTP() {
 			sender.Handler = mjpeg.RTPDepay(sender.Handler)
 		}
+
+	case core.CodecRAW:
+		sender.Handler = func(packet *rtp.Packet) {
+			if n, err := k.wr.Write(packet.Payload); err == nil {
+				k.Send += n
+			}
+		}
+
+		sender.Handler = mjpeg.Encoder(track.Codec, 5, sender.Handler)
 	}
 
 	sender.HandleRTP(track)

pkg/mjpeg/consumer.go

@@ -46,7 +46,7 @@ func (c *Consumer) AddTrack(media *core.Media, _ *core.Codec, track *core.Receiv
 	if track.Codec.IsRTP() {
 		sender.Handler = RTPDepay(sender.Handler)
 	} else if track.Codec.Name == core.CodecRAW {
-		sender.Handler = Encoder(track.Codec, sender.Handler)
+		sender.Handler = Encoder(track.Codec, 0, sender.Handler)
 	}
 
 	sender.HandleRTP(track)

pkg/mjpeg/helpers.go

@@ -52,12 +52,19 @@ func FixJPEG(b []byte) []byte {
 	return buf.Bytes()
 }
 
-func Encoder(codec *core.Codec, handler core.HandlerFunc) core.HandlerFunc {
+// Encoder convert YUV frame to Img.
+// Support skipping empty frames, for example if USB cam needs time to start.
+func Encoder(codec *core.Codec, skipEmpty int, handler core.HandlerFunc) core.HandlerFunc {
 	newImage := y4m.NewImage(codec.FmtpLine)
 
 	return func(packet *rtp.Packet) {
 		img := newImage(packet.Payload)
 
+		if skipEmpty != 0 && y4m.HasSameColor(img) {
+			skipEmpty--
+			return
+		}
+
 		buf := bytes.NewBuffer(nil)
 		if err := jpeg.Encode(buf, img, nil); err != nil {
 			return

pkg/y4m/y4m.go

@@ -123,3 +123,27 @@ func NewImage(fmtp string) func(frame []byte) image.Image {
 
 	return nil
 }
+
+// HasSameColor checks if all pixels has same color
+func HasSameColor(img image.Image) bool {
+	var pix []byte
+
+	switch img := img.(type) {
+	case *image.Gray:
+		pix = img.Pix
+	case *image.YCbCr:
+		pix = img.Y
+	}
+
+	if len(pix) == 0 {
+		return false
+	}
+
+	i0 := pix[0]
+	for _, i := range pix {
+		if i != i0 {
+			return false
+		}
+	}
+	return true
+}