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