sfu: fix data stats active window bitrate and duration units (#4922)

pkg/sfu/buffer/datastats.go

@@ -68,13 +68,14 @@ func (s *DataStats) ToProtoActive() *livekit.RTPStats {
 	if duration > s.params.WindowDuration.Nanoseconds() {
 		return &livekit.RTPStats{}
 	}
+	seconds := float64(duration) / 1e9
 
 	return &livekit.RTPStats{
 		StartTime: timestamppb.New(time.Unix(s.windowStart/1e9, s.windowStart%1e9)),
 		EndTime:   timestamppb.New(time.Unix(0, now)),
-		Duration:  float64(duration / 1e9),
+		Duration:  seconds,
 		Bytes:     uint64(s.windowBytes),
-		Bitrate:   float64(s.windowBytes) * 8 / float64(duration) / 1e9,
+		Bitrate:   float64(s.windowBytes) * 8 / seconds,
 	}
 }
 

pkg/sfu/buffer/datastats_test.go

@@ -51,3 +51,16 @@ func TestDataStats(t *testing.T) {
 	require.EqualValues(t, 100, r.Bytes)
 	require.NotZero(t, r.Bitrate)
 }
+
+func TestDataStatsActiveBitrateAndDuration(t *testing.T) {
+	stats := NewDataStats(DataStatsParam{WindowDuration: 10 * time.Second})
+
+	// 1000 bytes over a 1.5 second window is 8000 bits / 1.5 s
+	stats.windowStart = time.Now().Add(-1500 * time.Millisecond).UnixNano()
+	stats.windowBytes = 1000
+
+	r := stats.ToProtoActive()
+	require.EqualValues(t, 1000, r.Bytes)
+	require.InDelta(t, 1.5, r.Duration, 0.1)
+	require.InDelta(t, 8000/1.5, r.Bitrate, 0.1*8000/1.5)
+}