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package rtcp
import (
"encoding/binary"
"fmt"
)
// A SenderReport (SR) packet provides reception quality feedback for an RTP stream
type SenderReport struct {
// The synchronization source identifier for the originator of this SR packet.
SSRC uint32
// The wallclock time when this report was sent so that it may be used in
// combination with timestamps returned in reception reports from other
// receivers to measure round-trip propagation to those receivers.
NTPTime uint64
// Corresponds to the same time as the NTP timestamp (above), but in
// the same units and with the same random offset as the RTP
// timestamps in data packets. This correspondence may be used for
// intra- and inter-media synchronization for sources whose NTP
// timestamps are synchronized, and may be used by media-independent
// receivers to estimate the nominal RTP clock frequency.
RTPTime uint32
// The total number of RTP data packets transmitted by the sender
// since starting transmission up until the time this SR packet was
// generated.
PacketCount uint32
// The total number of payload octets (i.e., not including header or
// padding) transmitted in RTP data packets by the sender since
// starting transmission up until the time this SR packet was
// generated.
OctetCount uint32
// Zero or more reception report blocks depending on the number of other
// sources heard by this sender since the last report. Each reception report
// block conveys statistics on the reception of RTP packets from a
// single synchronization source.
Reports []ReceptionReport
// ProfileExtensions contains additional, payload-specific information that needs to
// be reported regularly about the sender.
ProfileExtensions []byte
}
const (
srHeaderLength = 24
srSSRCOffset = 0
srNTPOffset = srSSRCOffset + ssrcLength
ntpTimeLength = 8
srRTPOffset = srNTPOffset + ntpTimeLength
rtpTimeLength = 4
srPacketCountOffset = srRTPOffset + rtpTimeLength
srPacketCountLength = 4
srOctetCountOffset = srPacketCountOffset + srPacketCountLength
srOctetCountLength = 4
srReportOffset = srOctetCountOffset + srOctetCountLength
)
// Marshal encodes the SenderReport in binary
func (r SenderReport) Marshal() ([]byte, error) {
/*
* 0 1 2 3
* 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
* +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
* header |V=2|P| RC | PT=SR=200 | length |
* +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
* | SSRC of sender |
* +=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+
* sender | NTP timestamp, most significant word |
* info +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
* | NTP timestamp, least significant word |
* +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
* | RTP timestamp |
* +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
* | sender's packet count |
* +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
* | sender's octet count |
* +=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+
* report | SSRC_1 (SSRC of first source) |
* block +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
* 1 | fraction lost | cumulative number of packets lost |
* +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
* | extended highest sequence number received |
* +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
* | interarrival jitter |
* +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
* | last SR (LSR) |
* +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
* | delay since last SR (DLSR) |
* +=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+
* report | SSRC_2 (SSRC of second source) |
* block +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
* 2 : ... :
* +=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+
* | profile-specific extensions |
* +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
*/
rawPacket := make([]byte, r.len())
packetBody := rawPacket[headerLength:]
binary.BigEndian.PutUint32(packetBody[srSSRCOffset:], r.SSRC)
binary.BigEndian.PutUint64(packetBody[srNTPOffset:], r.NTPTime)
binary.BigEndian.PutUint32(packetBody[srRTPOffset:], r.RTPTime)
binary.BigEndian.PutUint32(packetBody[srPacketCountOffset:], r.PacketCount)
binary.BigEndian.PutUint32(packetBody[srOctetCountOffset:], r.OctetCount)
offset := srHeaderLength
for _, rp := range r.Reports {
data, err := rp.Marshal()
if err != nil {
return nil, err
}
copy(packetBody[offset:], data)
offset += receptionReportLength
}
if len(r.Reports) > countMax {
return nil, errTooManyReports
}
copy(packetBody[offset:], r.ProfileExtensions)
hData, err := r.Header().Marshal()
if err != nil {
return nil, err
}
copy(rawPacket, hData)
return rawPacket, nil
}
// Unmarshal decodes the SenderReport from binary
func (r *SenderReport) Unmarshal(rawPacket []byte) error {
/*
* 0 1 2 3
* 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
* +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
* header |V=2|P| RC | PT=SR=200 | length |
* +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
* | SSRC of sender |
* +=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+
* sender | NTP timestamp, most significant word |
* info +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
* | NTP timestamp, least significant word |
* +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
* | RTP timestamp |
* +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
* | sender's packet count |
* +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
* | sender's octet count |
* +=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+
* report | SSRC_1 (SSRC of first source) |
* block +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
* 1 | fraction lost | cumulative number of packets lost |
* +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
* | extended highest sequence number received |
* +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
* | interarrival jitter |
* +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
* | last SR (LSR) |
* +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
* | delay since last SR (DLSR) |
* +=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+
* report | SSRC_2 (SSRC of second source) |
* block +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
* 2 : ... :
* +=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+
* | profile-specific extensions |
* +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
*/
if len(rawPacket) < (headerLength + srHeaderLength) {
return errPacketTooShort
}
var h Header
if err := h.Unmarshal(rawPacket); err != nil {
return err
}
if h.Type != TypeSenderReport {
return errWrongType
}
packetBody := rawPacket[headerLength:]
r.SSRC = binary.BigEndian.Uint32(packetBody[srSSRCOffset:])
r.NTPTime = binary.BigEndian.Uint64(packetBody[srNTPOffset:])
r.RTPTime = binary.BigEndian.Uint32(packetBody[srRTPOffset:])
r.PacketCount = binary.BigEndian.Uint32(packetBody[srPacketCountOffset:])
r.OctetCount = binary.BigEndian.Uint32(packetBody[srOctetCountOffset:])
offset := srReportOffset
for i := 0; i < int(h.Count); i++ {
rrEnd := offset + receptionReportLength
if rrEnd > len(packetBody) {
return errPacketTooShort
}
rrBody := packetBody[offset : offset+receptionReportLength]
offset = rrEnd
var rr ReceptionReport
if err := rr.Unmarshal(rrBody); err != nil {
return err
}
r.Reports = append(r.Reports, rr)
}
if offset < len(packetBody) {
r.ProfileExtensions = packetBody[offset:]
}
if uint8(len(r.Reports)) != h.Count {
return errInvalidHeader
}
return nil
}
// DestinationSSRC returns an array of SSRC values that this packet refers to.
func (r *SenderReport) DestinationSSRC() []uint32 {
out := make([]uint32, len(r.Reports)+1)
for i, v := range r.Reports {
out[i] = v.SSRC
}
out[len(r.Reports)] = r.SSRC
return out
}
func (r *SenderReport) len() int {
repsLength := 0
for _, rep := range r.Reports {
repsLength += rep.len()
}
return headerLength + srHeaderLength + repsLength + len(r.ProfileExtensions)
}
// Header returns the Header associated with this packet.
func (r *SenderReport) Header() Header {
return Header{
Count: uint8(len(r.Reports)),
Type: TypeSenderReport,
Length: uint16((r.len() / 4) - 1),
}
}
func (r SenderReport) String() string {
out := fmt.Sprintf("SenderReport from %x\n", r.SSRC)
out += fmt.Sprintf("\tNTPTime:\t%d\n", r.NTPTime)
out += fmt.Sprintf("\tRTPTIme:\t%d\n", r.RTPTime)
out += fmt.Sprintf("\tPacketCount:\t%d\n", r.PacketCount)
out += fmt.Sprintf("\tOctetCount:\t%d\n", r.OctetCount)
out += "\tSSRC \tLost\tLastSequence\n"
for _, i := range r.Reports {
out += fmt.Sprintf("\t%x\t%d/%d\t%d\n", i.SSRC, i.FractionLost, i.TotalLost, i.LastSequenceNumber)
}
out += fmt.Sprintf("\tProfile Extension Data: %v\n", r.ProfileExtensions)
return out
}
