SdpTransform

Utilme.SdpTransform

SDP parser and writer for .NET. Transforms between SDP text, an object graph, and JSON — useful for VoIP and WebRTC work.

dotnet add package Utilme.SdpTransform

Requires .NET 10, no dependencies.

Parsing

using Utilme.SdpTransform;

Sdp? sdp = sdpText.ToSdp();                  // null if it cannot be parsed
SdpParseResult result = sdpText.ToSdpResult();  // same, plus every problem found

ToSdpResult never throws. IsValid says whether an Sdp was produced; Diagnostics carries a Warning for each line that was skipped and an Error if parsing had to stop, each with the 1-based line number from the original text.

How it works

Three representations, converted by paired extension methods:

SDP text  ⇄  object graph  ⇄  JSON

using Utilme.SdpTransform;

var sdp     = sdpText.ToSdp();            // text   -> object
var text    = sdp.ToText();               // object -> text
var json    = JsonSerializer.Serialize(sdp, options);
var back    = JsonSerializer.Deserialize<Sdp>(json)!.ToText();

Two design points that are not obvious from the file layout:

• Model classes carry their own grammar. Each model exposes const string tokens next to the properties they parse — Sdp.OriginIndicator = "o=", Candidate.Label = "candidate:". Parser and writer both consume these constants; SDP tokens are never hardcoded in the conversion code.
• All conversion lives in one file, Extensions/ModelExtensions.cs, as paired ToXxx(this string) / ToText(this Xxx) methods. ToSdp and ToText are the two entry points.

Enums are double-annotated: [JsonStringEnumMemberName] for the JSON wire form, [Display] for the SDP text form, converted through DisplayName() / EnumFromDisplayName<T>().

Documentation

Page	What's in it
Getting Started	Parsing, writing, JSON, diagnostics, gotchas
API Reference	Every public type and member
Design Notes	Why it looks like this; invariants to preserve
Refactor Log	What changed on the way to 26.9.7, and what is left

Backward compatibility

Additive-only, the same guarantee as Utilme.Result, enforced by an approval test over the whole public surface. See Design Notes.

Test coverage

149 tests — see Building and Testing. They began as a characterization suite pinning existing behaviour, defects included, which is what made the refactor safe.