Skip to content
Smelter logo Smelter logo Smelter

WHEP server

Node.js Browser (Client)

An output type that provides a WHEP server endpoint. It allows broadcasting a media stream to multiple clients simultaneously.

Smelter exposes WHEP endpoint on port 9000 under /whep/:output_id route. A different port can be configured with SMELTER_WHIP_WHEP_SERVER_PORT.

To connect new output, register it first with Smelter.registerOutput. This function returns an object containing the endpointRoute for the WHEP stream. You can then use this route to establish a WHEP connection.

Usage

whepServerOutputExample.tsx
import Smelter from "@swmansion/smelter-node";
import { View } from "@swmansion/smelter";


async function run() {
  const smelter = new Smelter();
  await smelter.init();
  const { endpointRoute } = await smelter.registerOutput("example", <View />, {
    type: "whep_server",
    video: {
      encoder: { type: "ffmpeg_h264" },
      resolution: { width: 1920, height: 1080 },
    }
  });
  // In this example, endpointRoute resolves to "/whep/example"
}
void run();

Reference

Type definitions 

type RegisterWhepServerOutput = {
  type: "whep_server";
  bearerToken?: string;
  video?: VideoOptions;
  audio?: AudioOptions;
}

Parameters for registering an output that sends composed video/audio as an WHEP stream.

Properties

bearerToken

Authentication token. If not provided, authentication is not required.

  • Type: string

video

Parameters of a video included in the WHEP stream.

audio

Parameters of an audio included in the WHEP stream.

VideoOptions

Type definitions 

type VideoOptions = {
  resolution: {
    width: number;
    height: number;
  };
  sendEosWhen?: OutputEndCondition;
  encoder: VideoEncoderOptions;
}

Parameters of a video source included in the WHEP stream.

Properties

resolution

Output resolution in pixels.

  • Type: { width: number; height: number;}

sendEosWhen

Condition for termination of the output stream based on the input streams states. If output includes both audio and video streams, then EOS needs to be sent for every type.

encoder

Video encoder options.

VideoEncoderOptions

Type definitions 

type VideoEncoderOptions =
  | ({ type: "ffmpeg_h264"; } & FfmpegH264EncoderOptions)
  | ({ type: "ffmpeg_vp8"; } & FfmpegVp8EncoderOptions)
  | ({ type: "ffmpeg_vp9"; } & FfmpegVp9EncoderOptions)
  | ({ type: "vulkan_h264"; } & VulkanH264EncoderOptions);

Configuration for the video encoder, based on the selected codec. Visit encoder documentation to learn more.

AudioOptions

Type definitions 

type AudioOptions = {
  channels?: "mono" | "stereo";
  mixingStrategy?: "sum_clip" | "sum_scale";
  sendEosWhen?: OutputEndCondition;
  encoder: AudioEncoderOptions;
}

Parameters of an audio source included in the WHEP stream.

Properties

channels

Channels configuration

  • Type: "mono" | "stereo"
  • Default value: "stereo"
  • Supported values:
    • mono - Mono audio (single channel).
    • stereo - Stereo audio (two channels).

mixingStrategy

Specifies how audio should be mixed.

  • Type: "sum_clip" | "sum_scale"
  • Default value: "sum_clip"
  • Supported values:
    • sum_clip - First, the input samples are summed. If the result exceeds the i16 PCM range, it is clipped.
    • sum_scale - First, the input samples are summed. If the result exceeds the i16 PCM range, the summed samples are scaled down by a factor to fit within the range.

sendEosWhen

Condition for termination of the output stream based on the input streams states. If output includes both audio and video streams, then EOS needs to be sent for every type.

encoder

Audio encoder options.

AudioEncoderOptions

Type definitions 

type AudioEncoderOptions =
  | { type: "opus"; } & OpusEncoderOptions;

Configuration for the audio encoder. Visit encoder documentation to learn more.

OutputEndCondition

Type definitions 

type OutputEndCondition =
  | { anyOf: string[]; }
  | { allOf: string[]; }
  | { anyInput: boolean; }
  | { allInputs: boolean; };

Defines when the output stream should end based on the state of the input streams. Only one of the nested fields can be set at a time.

By default, the input stream is considered finished/ended when:

  • TCP connection was dropped/closed.
  • RTCP Goodbye packet (BYE) was received.
  • MP4 track has ended.
  • Input was unregistered already (or never registered).

Properties

anyOf

List of the input streams. The output stream will terminate if any stream in the list finishes.

  • Type: string[]

allOf

List of the input streams. The output stream will terminate when all streams in the list finish.

  • Type: string[]

anyInput

Terminate the output stream if any of the input streams end, including streams added after the output was registered. Notably, the output stream will not terminate if no inputs were ever connected.

  • Type: boolean

allInputs

Terminate the output stream only when all input streams have finished. Notably, the output stream will terminate if no inputs were ever connected.

  • Type: boolean