From 67d4106adcc31c58d64cee098ef5293d21e0504d Mon Sep 17 00:00:00 2001
From: Alessandro Ros <aler9.dev@gmail.com>
Date: Mon, 8 May 2023 13:54:51 +0200
Subject: [PATCH] rtptime: fix time encoding on arm32 (#274) (#277)

---
 client.go                   |  2 +-
 pkg/rtptime/decoder.go      | 14 +++++++++-----
 pkg/rtptime/encoder.go      | 19 ++++++++++++++-----
 pkg/rtptime/encoder_test.go |  3 +++
 4 files changed, 27 insertions(+), 11 deletions(-)

diff --git a/client.go b/client.go
index 2fafb4c0..682fcb77 100644
--- a/client.go
+++ b/client.go
@@ -943,7 +943,7 @@ func (c *Client) do(req *base.Request, skipResponse bool, allowFrames bool) (*ba
 		c.session = sx.Session
 
 		if sx.Timeout != nil && *sx.Timeout > 0 {
-			c.keepalivePeriod = time.Duration(float64(*sx.Timeout)*0.8) * time.Second
+			c.keepalivePeriod = time.Duration(((*sx.Timeout)*10)/8) * time.Second
 		}
 	}
 
diff --git a/pkg/rtptime/decoder.go b/pkg/rtptime/decoder.go
index ede7159f..016c4ed2 100644
--- a/pkg/rtptime/decoder.go
+++ b/pkg/rtptime/decoder.go
@@ -7,6 +7,14 @@ import (
 
 const negativeThreshold = 0xFFFFFFFF / 2
 
+// avoid an int64 overflow and preserve resolution by splitting division into two parts:
+// first add the integer part, then the decimal part.
+func multiplyAndDivide(v, m, d time.Duration) time.Duration {
+	secs := v / d
+	dec := v % d
+	return (secs*m + dec*m/d)
+}
+
 // Decoder is a RTP timestamp decoder.
 type Decoder struct {
 	clockRate   time.Duration
@@ -42,9 +50,5 @@ func (d *Decoder) Decode(ts uint32) time.Duration {
 		d.overall += time.Duration(diff)
 	}
 
-	// avoid an int64 overflow and preserve resolution by splitting division into two parts:
-	// first add the integer part, then the decimal part.
-	secs := d.overall / d.clockRate
-	dec := d.overall % d.clockRate
-	return secs*time.Second + dec*time.Second/d.clockRate
+	return multiplyAndDivide(d.overall, time.Second, d.clockRate)
 }
diff --git a/pkg/rtptime/encoder.go b/pkg/rtptime/encoder.go
index 259a7b89..cb00750f 100644
--- a/pkg/rtptime/encoder.go
+++ b/pkg/rtptime/encoder.go
@@ -1,25 +1,34 @@
 package rtptime
 
 import (
-	"math"
 	"time"
 )
 
+func divCeil(n, d uint64) uint64 {
+	v := n / d
+	if (n % d) != 0 {
+		v++
+	}
+	return v
+}
+
 // Encoder is a RTP timestamp encoder.
 type Encoder struct {
-	clockRate        float64
+	clockRate        time.Duration
 	initialTimestamp time.Duration
 }
 
 // NewEncoder allocates an Encoder.
 func NewEncoder(clockRate int, initialTimestamp uint32) *Encoder {
 	return &Encoder{
-		clockRate:        float64(clockRate),
-		initialTimestamp: time.Duration(math.Ceil(float64(initialTimestamp) * float64(time.Second) / float64(clockRate))),
+		clockRate: time.Duration(clockRate),
+		// ((2^32) * 1000000000) is less than 2^63
+		initialTimestamp: time.Duration(divCeil(uint64(initialTimestamp)*uint64(time.Second), uint64(clockRate))),
 	}
 }
 
 // Encode encodes a timestamp.
 func (e *Encoder) Encode(ts time.Duration) uint32 {
-	return uint32((e.initialTimestamp + ts).Seconds() * e.clockRate)
+	ts = e.initialTimestamp + ts
+	return uint32(multiplyAndDivide(ts, e.clockRate, time.Second))
 }
diff --git a/pkg/rtptime/encoder_test.go b/pkg/rtptime/encoder_test.go
index a4e05116..d5313f87 100644
--- a/pkg/rtptime/encoder_test.go
+++ b/pkg/rtptime/encoder_test.go
@@ -12,6 +12,9 @@ func TestEncoder(t *testing.T) {
 
 	ts := e.Encode(0)
 	require.Equal(t, uint32(12345), ts)
+
+	ts = e.Encode(3 * time.Second / 2)
+	require.Equal(t, uint32(12345+135000), ts)
 }
 
 func BenchmarkEncoder(b *testing.B) {