ServerStream

Complete API reference for the ServerStream type.

ServerStream represents a media stream on the server side. It stores the stream description, manages SSRC allocation, distributes packets to all active reader sessions, and optionally manages multicast listeners.

A ServerStream is created by the application and shared between the publisher session and all reader sessions. The publisher writes packets into the stream via WritePacketRTP / WritePacketRTCP, and the stream fans the packets out to every active reader.

Struct fields

Server · *Server · required

The server instance this stream belongs to. Must be set before calling Initialize().

Desc · *description.Session · required

The session description (SDP) that describes the media contained in this stream. Must be set before calling Initialize().

MulticastParams · map[*description.Media]StreamMediaMulticastParams

Optional per-media multicast configuration. When set, the specified IP and ports are used instead of the server’s auto-assigned multicast addresses.

StreamMediaMulticastParams fields:

Field	Type	Description
IP	net.IP	Multicast group IP
RTPPort	int	Multicast RTP port
RTCPPort	int	Multicast RTCP port

---

Methods

Lifecycle

Initialize

func (st *ServerStream) Initialize() error

Initializes the stream. Allocates local SSRCs for each media format, sets up SRTP contexts when the parent server uses TLS, and prepares internal data structures. Must be called after setting Server and Desc, and after the server has been started with Server.Start().

error · error

Non-nil if the server is not present or not yet initialized, or if SSRC/SRTP setup fails.

---

Close

func (st *ServerStream) Close()

Closes the stream. All reader sessions currently subscribed to this stream are closed immediately. After Close() is called, subsequent WritePacketRTP / WritePacketRTCP calls return ErrServerStreamClosed.

Packet writing

WritePacketRTP

func (st *ServerStream) WritePacketRTP(medi *description.Media, pkt *rtp.Packet) error

Writes an RTP packet to all active readers of the stream. Uses the current wall clock as the NTP timestamp for RTCP sender reports. Thread-safe.

medi · *description.Media · required

The media track the packet belongs to. Must be one of the medias in Desc.

pkt · *rtp.Packet · required

The RTP packet to distribute.

error · error

ErrServerStreamClosed if the stream has been closed; otherwise a write error.

---

WritePacketRTPWithNTP

func (st *ServerStream) WritePacketRTPWithNTP(
    medi *description.Media,
    pkt *rtp.Packet,
    ntp time.Time,
) error

Like WritePacketRTP but accepts an explicit NTP timestamp. The NTP value is included in periodic RTCP sender reports sent to readers. Use this when you have an accurate external clock source.

medi · *description.Media · required

The media track the packet belongs to.

pkt · *rtp.Packet · required

The RTP packet to distribute.

ntp · time.Time · required

Absolute NTP timestamp of the packet.

error · error

ErrServerStreamClosed if the stream has been closed; otherwise a write error.

---

WritePacketRTCP

func (st *ServerStream) WritePacketRTCP(medi *description.Media, pkt rtcp.Packet) error

Writes an RTCP packet to all active readers of the stream. Thread-safe.

medi · *description.Media · required

The media track the packet belongs to.

pkt · rtcp.Packet · required

The RTCP packet to distribute.

error · error

ErrServerStreamClosed if the stream has been closed; otherwise a write error.

Statistics

Stats

func (st *ServerStream) Stats() *ServerStreamStats

Returns a snapshot of stream statistics.

ServerStreamStats fields:

Field	Type	Description
OutboundBytes	uint64	Total bytes written to readers
OutboundRTPPackets	uint64	Total RTP packets distributed
OutboundRTCPPackets	uint64	Total RTCP packets distributed
Medias	map[*description.Media]ServerStreamStatsMedia	Per-media statistics

ServerStreamStatsMedia fields:

Field	Type	Description
OutboundBytes	uint64	Bytes written for this media
OutboundRTCPPackets	uint64	RTCP packets distributed for this media
Formats	map[format.Format]ServerStreamStatsFormat	Per-format statistics

ServerStreamStatsFormat fields:

Field	Type	Description
OutboundRTPPackets	uint64	RTP packets distributed for this format
LocalSSRC	uint32	Locally assigned SSRC for this format

---

Usage example

// Create stream after server is started
stream := &gortsplib.ServerStream{
    Server: server,
    Desc:   sessionDesc, // *description.Session from SDP
}
err := stream.Initialize()
if err != nil {
    panic(err)
}
defer stream.Close()

// In OnDescribe and OnSetup handlers, return this stream.
// The server will add reader sessions to it automatically.

// Write packets from a publisher goroutine:
err = stream.WritePacketRTP(media, rtpPacket)
if err != nil {
    log.Println(err)
}

The ServerStream is not associated with any particular publisher connection. It is the application’s responsibility to create the stream when a publisher arrives (e.g. in OnAnnounce) and close it when the publisher leaves (e.g. in OnSessionClose).