HLS

Node.js Browser (Client)

An output type that allows streaming video and audio from Smelter over HLS. It writes HLS playlist to disk, but user needs to handle serving the files on their own.

Usage

hlsOutputExample.tsx

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

async function run() {
  const smelter = new Smelter();
  await smelter.init();
  await smelter.registerOutput("example", <View />, {
    type: 'hls',
    serverPath: './output.m3u8',
    video: {
      encoder: {
        type: 'ffmpeg_h264',
        preset: 'ultrafast',
      },
      resolution: {
        width: 1920,
        height: 1080,
      },
    },
    audio: {
      channels: 'stereo',
      encoder: {
        type: 'aac',
      },
    },
  });
}
void run();

Reference

Type definitions

type RegisterHlsOutput = {
  type: "hls";
  serverPath: string;
  maxPlaylistSize?: number;
  video?: VideoOptions;
  audio?: AudioOptions;
}

Properties

serverPath

Path to the HLS playlist file, specifying its location on the server where Smelter is deployed.

• Type: string

---

maxPlaylistSize

Number of segments kept in the playlist. When the limit is reached the oldest segment is removed. If not specified, no segments will removed.

• Type: number

---

video

Video track configuration.

• Type: VideoOptions

---

audio

Audio track configuration.

• Type: AudioOptions

VideoOptions

Type definitions

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

Parameters of a video source included in the 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.

• Type: OutputEndCondition

---

encoder

Video encoder options.

• Type: VideoEncoderOptions

VideoEncoderOptions

Type definitions

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

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

• FFmpeg H264
• Vulkan H264

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 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.

• Type: OutputEndCondition

---

encoder

Audio encoder options.

• Type: AudioEncoderOptions

AudioEncoderOptions

Type definitions

type AudioEncoderOptions =
  | { type: "aac"; } & AacEncoderOptions;

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

• AAC

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.
• MP5 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