1 files changed, 78 insertions, 0 deletions
diff --git a/vendor/github.com/pion/rtp/abssendtimeextension.go b/vendor/github.com/pion/rtp/abssendtimeextension.go
new file mode 100644
index 0000000..fc9731d
--- /dev/null
+++ b/vendor/github.com/pion/rtp/abssendtimeextension.go
@@ -0,0 +1,78 @@
+package rtp
+
+import (
+	"time"
+)
+
+const (
+	absSendTimeExtensionSize = 3
+)
+
+// AbsSendTimeExtension is a extension payload format in
+// http://www.webrtc.org/experiments/rtp-hdrext/abs-send-time
+type AbsSendTimeExtension struct {
+	Timestamp uint64
+}
+
+// Marshal serializes the members to buffer.
+func (t *AbsSendTimeExtension) Marshal() ([]byte, error) {
+	return []byte{
+		byte(t.Timestamp & 0xFF0000 >> 16),
+		byte(t.Timestamp & 0xFF00 >> 8),
+		byte(t.Timestamp & 0xFF),
+	}, nil
+}
+
+// Unmarshal parses the passed byte slice and stores the result in the members.
+func (t *AbsSendTimeExtension) Unmarshal(rawData []byte) error {
+	if len(rawData) < absSendTimeExtensionSize {
+		return errTooSmall
+	}
+	t.Timestamp = uint64(rawData[0])<<16 | uint64(rawData[1])<<8 | uint64(rawData[2])
+	return nil
+}
+
+// Estimate absolute send time according to the receive time.
+// Note that if the transmission delay is larger than 64 seconds, estimated time will be wrong.
+func (t *AbsSendTimeExtension) Estimate(receive time.Time) time.Time {
+	receiveNTP := toNtpTime(receive)
+	ntp := receiveNTP&0xFFFFFFC000000000 | (t.Timestamp&0xFFFFFF)<<14
+	if receiveNTP < ntp {
+		// Receive time must be always later than send time
+		ntp -= 0x1000000 << 14
+	}
+
+	return toTime(ntp)
+}
+
+// NewAbsSendTimeExtension makes new AbsSendTimeExtension from time.Time.
+func NewAbsSendTimeExtension(sendTime time.Time) *AbsSendTimeExtension {
+	return &AbsSendTimeExtension{
+		Timestamp: toNtpTime(sendTime) >> 14,
+	}
+}
+
+func toNtpTime(t time.Time) uint64 {
+	var s uint64
+	var f uint64
+	u := uint64(t.UnixNano())
+	s = u / 1e9
+	s += 0x83AA7E80 // offset in seconds between unix epoch and ntp epoch
+	f = u % 1e9
+	f <<= 32
+	f /= 1e9
+	s <<= 32
+
+	return s | f
+}
+
+func toTime(t uint64) time.Time {
+	s := t >> 32
+	f := t & 0xFFFFFFFF
+	f *= 1e9
+	f >>= 32
+	s -= 0x83AA7E80
+	u := s*1e9 + f
+
+	return time.Unix(0, int64(u))
+}