codec/mjpeg/jpeg.go: moved get24 to bottom of file and gave comment.

codec/mjpeg/extract.go

@@ -73,7 +73,9 @@ func (e *Extractor) Extract(dst io.Writer, src io.Reader, delay time.Duration) e
 		}
 
 		err = ctx.ParsePayload(p, m)
-		if err != nil {
+		switch err {
+		case ErrNoFrameStart: // If no frame start then we continue until we get one.
+		default:
 			return fmt.Errorf("could not parse JPEG scan: %w", err)
 		}
 	}

codec/mjpeg/jpeg.go

@@ -91,6 +91,7 @@ var (
 	ErrReservedQ            = errors.New("q value is reserved")
 	ErrUnimplementedType    = errors.New("unimplemented RTP/JPEG type")
 	ErrUnsupportedPrecision = errors.New("unsupported precision")
+	ErrNoFrameStart         = errors.New("missing start of frame")
 )
 
 // Slices used in the creation of huffman tables.
@@ -260,7 +261,7 @@ func (c *Context) ParsePayload(p []byte, m bool) error {
 
 	if c.blen == 0 {
 		// Must have missed start of frame? So ignore and wait for start.
-		return nil
+		return ErrNoFrameStart
 	}
 
 	// TODO: check that timestamp is consistent
@@ -290,10 +291,6 @@ func (c *Context) ParsePayload(p []byte, m bool) error {
 	return nil
 }
 
-func get24(p []byte) int {
-	return int(p[0]<<16) | int(p[1]<<8) | int(p[2])
-}
-
 // writeHeader writes a JPEG header to the writer w.
 func writeHeader(p []byte, _type, width, height, nbqTab int, dri uint16, qtable []byte) int {
 	width <<= 3
@@ -451,3 +448,8 @@ func clip(v, min, max int) int {
 
 	return v
 }
+
+// get24 parses an int24 from p using big endian order.
+func get24(p []byte) int {
+	return int(p[0]<<16) | int(p[1]<<8) | int(p[2])
+}