From c7d8083a4c750e4b9fa1993d2acbbc1e9af4ee74 Mon Sep 17 00:00:00 2001
From: aler9 <46489434+aler9@users.noreply.github.com>
Date: Tue, 18 Jan 2022 11:51:52 +0100
Subject: [PATCH] rtptimedec: fix decoding error of 1ns during overflow

---
 pkg/rtptimedec/decoder.go      |  4 ++--
 pkg/rtptimedec/decoder_test.go | 22 ++++++++++++++++++----
 2 files changed, 20 insertions(+), 6 deletions(-)

diff --git a/pkg/rtptimedec/decoder.go b/pkg/rtptimedec/decoder.go
index 1220d338..89d91eae 100644
--- a/pkg/rtptimedec/decoder.go
+++ b/pkg/rtptimedec/decoder.go
@@ -28,10 +28,10 @@ func (d *Decoder) Decode(ts uint32) time.Duration {
 		diff := ts64 - *d.tsPrev
 		switch {
 		case diff < -0xFFFFFF: // overflow
-			d.tsAdd += 0xFFFFFFFF
+			d.tsAdd += 0x100000000
 
 		case diff > 0xFFFFFF: // timestamp overflowed then went back
-			d.tsAdd -= 0xFFFFFFFF
+			d.tsAdd -= 0x100000000
 		}
 	}
 
diff --git a/pkg/rtptimedec/decoder_test.go b/pkg/rtptimedec/decoder_test.go
index df174233..721ecc1e 100644
--- a/pkg/rtptimedec/decoder_test.go
+++ b/pkg/rtptimedec/decoder_test.go
@@ -10,11 +10,25 @@ import (
 func TestOverflow(t *testing.T) {
 	d := New(90000)
 
-	pts := d.Decode(4294877295)
+	i := uint32(4294877296)
+	pts := d.Decode(i)
 	require.Equal(t, time.Duration(0), pts)
 
-	pts = d.Decode(90000)
+	// 1st overflow
+	i += 90000 * 2
+	pts = d.Decode(i)
 	require.Equal(t, 2*time.Second, pts)
+
+	// reach 4294890000 slowly
+	for ; i < 4294890000; i += 90000 * 10 {
+		pts = d.Decode(i)
+		require.Equal(t, 2*time.Second+time.Second*time.Duration(i-90000)/90000, pts)
+	}
+
+	// 2nd overflow
+	i += 90000 * 10
+	pts = d.Decode(i)
+	require.Equal(t, 47732*time.Second, pts)
 }
 
 func TestOverflowAndBack(t *testing.T) {
@@ -23,7 +37,7 @@ func TestOverflowAndBack(t *testing.T) {
 	pts := d.Decode(4294877296)
 	require.Equal(t, time.Duration(0), pts)
 
-	pts = d.Decode(90001)
+	pts = d.Decode(90000)
 	require.Equal(t, 2*time.Second, pts)
 
 	pts = d.Decode(4294877296)
@@ -35,6 +49,6 @@ func TestOverflowAndBack(t *testing.T) {
 	pts = d.Decode(4294877296)
 	require.Equal(t, time.Duration(0), pts)
 
-	pts = d.Decode(90001)
+	pts = d.Decode(90000)
 	require.Equal(t, 2*time.Second, pts)
 }