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Import path: github.com/bluenviron/gortsplib/v5/pkg/description

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Session

A Session is the top-level description of an RTSP stream. It maps directly to an SDP session description and holds one or more Media entries. 
type Session struct {
    BaseURL      *base.URL
    Title        string
    Multicast    bool
    KeyMgmtMikey *mikey.Message
    FECGroups    []SessionFECGroup
    Medias       []*Media
}

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Fields

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BaseURL
*base.URL
Base URL of the stream. Populated when the session is received from a server; read-only.
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Title
string
Optional human-readable title of the stream. Maps to the SDP s= field.
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Multicast
bool
When true, the SDP connection address is set to a multicast address (224.1.0.0).
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KeyMgmtMikey
*mikey.Message
Optional MIKEY key-management attribute (a=key-mgmt). Used for SRTP streams.
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FECGroups
[]SessionFECGroup
Forward Error Correction groups as defined in RFC 5109. Each group is a slice of media IDs.
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Medias
[]*Media
required
The list of media streams in this session. At least one entry is required for a valid SDP.

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Methods

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FindFormat

func (d *Session) FindFormat(forma any) *Media
Searches all medias in the session for a format of the given type. When found, it stores the format in forma (a pointer to the target format variable) and returns the owning *Media. Returns nil if no matching format is found. 
var forma *format.H264
media := desc.FindFormat(&forma)
if media != nil {
    // forma is now populated
}

​
Marshal

func (d Session) Marshal() ([]byte, error)
Encodes the session as an SDP byte slice.

​
Unmarshal

func (d *Session) Unmarshal(ssd *sdp.SessionDescription) error
Decodes the session from a parsed SDP session description.

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Media

A Media represents a single media stream (e.g., one video track or one audio track) within a session. 
type Media struct {
    Type          MediaType
    ID            string
    IsBackChannel bool
    Profile       headers.TransportProfile
    KeyMgmtMikey  *mikey.Message
    Control       string
    Formats       []format.Format
}

​
Fields

​
Type
MediaType
required
The type of this media stream: MediaTypeVideo, MediaTypeAudio, or MediaTypeApplication.
​
ID
string
Optional media identifier (a=mid). Must be alphanumeric. Used when multiple media sections are bundled (RFC 5888).
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IsBackChannel
bool
When true, the media is a back channel (e.g., two-way audio on an IP camera). Serialized as a=sendonly in SDP.
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Profile
headers.TransportProfile
The RTP profile: TransportProfileAVP (default) or TransportProfileSAVP (for SRTP).
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KeyMgmtMikey
*mikey.Message
Optional per-media MIKEY key-management attribute.
​
Control
string
The a=control attribute value. Used to build the per-media RTSP URL for SETUP requests.
​
Formats
[]format.Format
required
The RTP payload formats carried by this media stream. At least one format is required.

​
Methods

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FindFormat

func (m Media) FindFormat(forma any) bool
Searches the media’s Formats slice for a format whose concrete type matches the element type of forma. On success, sets *forma and returns true.

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URL

func (m Media) URL(contentBase *base.URL) (*base.URL, error)
Returns the absolute RTSP URL for this media, resolved against contentBase (the Content-Base header from the server). Returns an error when contentBase is nil.

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Marshal

func (m Media) Marshal() (*psdp.MediaDescription, error)
Encodes the media as a pion SDP MediaDescription.

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Unmarshal

func (m *Media) Unmarshal(md *psdp.MediaDescription) error
Decodes the media from a pion SDP MediaDescription.

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MediaType

MediaType is a string type used to classify a media stream.
ConstantValueDescription
MediaTypeVideo"video"Video stream
MediaTypeAudio"audio"Audio stream
MediaTypeApplication"application"Application data stream (e.g., metadata, KLV)

​
SessionFECGroup

type SessionFECGroup []string
A SessionFECGroup is a slice of media IDs that form a Forward Error Correction group (RFC 5109). Groups are serialized as a=group:FEC <id1> <id2> ... in SDP.

​
Code example

Building a session description for a recording client that sends H.264 video: 
import (
    "github.com/bluenviron/gortsplib/v5/pkg/description"
    "github.com/bluenviron/gortsplib/v5/pkg/format"
)

desc := &description.Session{
    Medias: []*description.Media{
        {
            Type: description.MediaTypeVideo,
            Formats: []format.Format{
                &format.H264{
                    PayloadTyp:        96,
                    PacketizationMode: 1,
                },
            },
        },
    },
}
Searching for a specific format across all medias: 
var h264Fmt *format.H264
media := desc.FindFormat(&h264Fmt)
if media == nil {
    // no H264 track found
}

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