fix framenumber test (#2942)

pkg/sfu/videolayerselector/framenumberwrapper.go

@@ -41,7 +41,7 @@ func (f *FrameNumberWrapper) UpdateAndGet(new uint64, updateOffset bool) uint64
 		new16 := uint16(new + f.offset)
 		last16 := uint16(f.last + f.offset)
 		// if new frame number wraps around and is considered as earlier by client, increase offset to make it later
-		if diff := new16 - last16; diff > 0x8000 || (diff == 0x8000 && new16 <= last16) {
+		if diff := new16 - last16; diff > 0x8000 || (diff == 0x8000 && new16 < last16) {
 			// increase offset by 6000, nearly 10 seconds for 30fps video with 3 spatial layers
 			prevOffset := f.offset
 			f.offset += uint64(65535 - diff + 6000)

pkg/sfu/videolayerselector/framenumberwrapper_test.go

@@ -65,6 +65,12 @@ func TestFrameNumberWrapper(t *testing.T) {
 		// frame out of order
 		firstF = secondF
 		secondF = getFrame(firstF, false)
+		// it is possile that an out of order non-keyframe has been converted to in order frame number if the diff is 32768
+		// that is ok because the client can't decode in such case and always need to wait for the key frame.
+		// so it is just a failure of test case and increase the frame number here.
+		if secondF-firstF == 0x8000 {
+			secondF++
+		}
 		testFrameOrder(firstF, false, secondF, false, false)
 
 		// key frame in order
@@ -92,5 +98,11 @@ func getFrame(base uint16, inorder bool) uint16 {
 	if inorder {
 		return base + uint16(rand.Intn(0x8000))
 	}
-	return base + uint16(rand.Intn(0x8000)) + 0x8000
+
+	for {
+		ret := base + uint16(rand.Intn(0x8000)) + 0x8000
+		if !inOrder(ret, base) {
+			return ret
+		}
+	}
 }