rtp*: move time decoder into own package

pkg/rtptimedec/decoder_test.go

@@ -0,0 +1,24 @@
+package rtptimedec
+
+import (
+	"testing"
+	"time"
+
+	"github.com/stretchr/testify/require"
+)
+
+func TestOverflow(t *testing.T) {
+	d := New(90000)
+	var pts time.Duration
+
+	for _, ts := range []uint32{
+		4294877296,
+		90001,
+		3240090001,
+		565122706,
+	} {
+		pts = d.Decode(ts)
+	}
+
+	require.Equal(t, 15*60*60*time.Second+2*time.Second, pts)
+}