SdpTransform API Reference

Utilme.SdpTransform — API Reference

Assembly Utilme.SdpTransform, version 26.9.7, target net10.0, no dependencies. Everything lives in the Utilme.SdpTransform namespace.

The whole surface is pinned by an approval test against a checked-in baseline — see Design Notes.

---

Entry points

ModelExtensions holds every converter as an extension method.

Member	Notes
Sdp ToSdp(this string)	Parses SDP text. Returns null if it cannot be parsed. Discards diagnostics.
SdpParseResult ToSdpResult(this string)	Parses and reports every problem. Never throws.
string ToText(this Sdp)	Writes a document. Output is byte-identical to what it parsed from.

---

SdpParseResult

Member	Notes
Sdp Sdp	The parsed document, or null if parsing could not complete.
bool IsValid	Whether an Sdp was produced.
IReadOnlyList<SdpDiagnostic> Diagnostics	Every problem, in document order.
bool HasDiagnostics	Whether anything was reported.

A valid result may still carry warnings for lines that were skipped.

SdpDiagnostic

Member	Notes
SdpDiagnosticSeverity Severity	Warning (line skipped, parsing continued) or Error (parsing stopped).
int LineNumber	1-based, counting blank lines. 0 when not attributable to one line.
string Line	The offending line, trimmed.
string Message	What went wrong.
string ToString()	Warning (line 6): Unsupported session field: x=bad

---

The document

Sdp

Property	SDP	Notes
int ProtocolVersion	v=
Origin Origin	o=	Mandatory.
string SessionName	s=	Mandatory. Sdp.DefaultSessionName is "-".
string SessionInformation	i=	Optional.
Uri Uri	u=	Optional.
IList<string> EmailAddresses	e=	Optional, repeatable.
IList<string> PhoneNumbers	p=	Optional, repeatable.
ConnectionData ConnectionData	c=	Here or per media description.
IList<Bandwidth> Bandwidths	b=	Optional, repeatable.
IList<Timing> Timings	t=	Mandatory. Seconds since 1900.
IList<RepeatTime> RepeatTimes	r=	Optional, repeatable.
IList<TimeZone> TimeZones	z=	Optional. Parsed in pairs.
EncryptionKey EncryptionKey	k=	Optional.
Attributes Attributes	a=	Optional.
IList<MediaDescription> MediaDescriptions	m=	Optional.

Sdp.CRLF is "\r\n" — the only line separator the parser accepts. Each field also exposes its indicator as a const, e.g. Sdp.OriginIndicator is "o=".

MediaDescription

MediaType Media, int Port, string Proto, IList<string> Fmts, plus the session overrides Information, ConnectionData, Bandwidths, EncryptionKey and Attributes.

Attributes

Shared by Sdp and MediaDescription — both scopes parse and write the same set.

Binary (bool?, present or absent): ExtmapAllowMixed, IceLite, RtcpMux, RtcpRsize, SendRecv, SendOnly, RecvOnly, EndOfCandidates.

Single-valued: Group, MsidSemantic, Mid, Msid, IceUfrag, IcePwd, IceOptions, Fingerprint, Rtcp, Setup, SctpPort, MaxMessageSize, Simulcast.

Repeatable (IList<T>): Candidates, Ssrcs, SsrcGroups, Rids, Rtpmaps, Fmtps, RtcpFbs, Extmaps.

Each attribute type carries its own label, e.g. Candidate.Label is "candidate:".

---

Enums

Each member's SDP token is its [Display] name; matching on input ignores case, output is always canonical.

Enum	Tokens
NetType	IN
AddrType	IP4, IP6
MediaType	audio, video, text, application, message
BandwidthType	AS, CT, RS, RR, TIAS
Direction	sendrecv, sendonly, recvonly, inactive
RidDirection	recv, send
SetupRole	active, passive, actpass, holdconn
CandidateType	host, srflx, prlfx, relay
CandidateTransport	udp, tcp
GroupSemantics	LS, FID, BUNDLE
HashFunction	sha-1, sha-224, sha-256, sha-384, sha-512, md2, md5
EncryptionKeyMethod	clear, base64, uri, prompt
SdpDiagnosticSeverity	(not an SDP token — Warning, Error)

---

Per-line converters

Every field and attribute has a ToXxx(this string) / ToText(this Xxx) pair, so a single line can be converted on its own.

Session fields: ToProtocolVersion, ToOrigin, ToSessionName, ToInformation, ToUri, ToEmailAddresses, ToPhoneNumbers, ToConnectionData, ToBandwidth, ToTiming, ToRepeatTime, ToTimeZones, ToEncryptionKey, ToMediaDescription.

Attributes: ToGroup, ToMsidSemantic, ToMid, ToMsid, ToIceUfrag, ToIcePwd, ToIceOptions, ToFingerprint, ToRtcp, ToSetup, ToSctpPort, ToMaxMessageSize, ToCandidate, ToSsrc, ToSsrcGroup, ToRid, ToSimulcast, ToRtpmap, ToFmtp, ToRtcpFb, ToExtmap.

Each has a matching ToText. A few write-side helpers are named differently where the input type is string or int and would otherwise collide: ToProtocolVersionText, ToSessionNameText, ToInformationText, ToEmailAddressesText, ToPhoneNumbersText.

Helpers: ToFmtp(this Dictionary<string, object>, int payloadType) and ToDictionary(this Fmtp) convert format parameters to and from a dictionary. HexadecimalStringToByteArray and ToSeconds(this string) — which accepts d, h, m and s suffixes — are public utilities.