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RTP

Node.js Browser (Client)

An output type that allows streaming video and audio from Smelter over RTP.

Usage

rtpOutputExample.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: "rtp_stream",
    port: 8001,
    transportProtocol: "tcp_server",
    video: {
      encoder: { type: "ffmpeg_h264" },
      resolution: { width: 1920, height: 1080 },
    }
  });
  // At this point you can connect to 8001 TCP port
  // and start receiving RTP traffic.
}
void run();

Reference

Type definitions 

type RegisterRtpOutput = {
  type: "rtp_stream";
  port: string | number;
  ip?: string;
  transportProtocol?: "udp" | "tcp_server";
  video?: VideoOptions;
  audio?: AudioOptions;
}

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

Properties

port

Depends on the value of the transportProtocol field:

  • udp - Specifies a UDP port number to which RTP packets will be sent.
  • tcp_server - Specifies a local TCP port number or a range of ports that Smelter will listen to for incoming connections.

  • Type: string | number

transportProtocol

Transport layer protocol that will be used to send RTP packets.

  • Type: "udp" | "tcp_server"
  • Default value: udp
  • Supported values:
    • udp - UDP protocol.
    • tcp_server - TCP protocol where Smelter is the server side of the connection.

ip

IP address to which RTP packets should be sent. This field is only valid if transportProtocol field is set to udp.

  • Type: string | number

video

Parameters of a video included in the RTP stream.

audio

Parameters of an audio included in the RTP stream.

VideoOptions

Type definitions 

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

Parameters of a video source included in the RTP 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";
      preset?:
        | "ultrafast"
        | "superfast"
        | "veryfast"
        | "faster"
        | "fast"
        | "medium"
        | "slow"
        | "slower"
        | "veryslow"
        | "placebo";
      pixelFormat?: "yuv420p" | "yuv422p" | "yuv444p";
      ffmpegOptions?: Record<string, string>;
    }
  | {
      type: "ffmpeg_vp8";
      ffmpegOptions?: Record<string, string>;
    }
  | {
      type: "ffmpeg_vp9";
      pixelFormat?: "yuv420p" | "yuv422p" | "yuv444p";
      ffmpegOptions?: Record<string, string>;
    }
  | {
      type: "vulkan_h264";
      bitrate?: { averageBitrate: number; maxBitrate: number; } | number;
    };

Configuration for the video encoder, based on the selected codec.

Properties (type: “ffmpeg_h264”)

preset

Video output encoder preset. Visit FFmpeg docs to learn more.

  • Type: "ultrafast" | "superfast" | "veryfast" | "faster" | "fast" | "medium" | "slow" | "slower" | "veryslow" | "placebo"
  • Default value: fast
  • Supported values:
    • ultrafast
    • superfast
    • veryfast
    • faster
    • fast
    • medium
    • slow
    • slower
    • veryslow
    • placebo

pixelFormat

Encoder pixel format

  • Type: "yuv420p" | "yuv422p" | "yuv444p"
  • Default value: yuv420p
  • Supported values:
    • yuv420p
    • yuv422p
    • yuv444p

ffmpegOptions

Raw FFmpeg encoder options. Visit FFmpeg docs to learn more.

  • Type: Record<string, string>

Properties (type: “ffmpeg_vp8”)

ffmpegOptions

Raw FFmpeg encoder options. Visit FFmpeg docs to learn more.

  • Type: Record<string, string>

Properties (type: “ffmpeg_vp9”)

pixelFormat

Encoder pixel format

  • Type: "yuv420p" | "yuv422p" | "yuv444p"
  • Default value: yuv420p
  • Supported values:
    • yuv420p
    • yuv422p
    • yuv444p

ffmpegOptions

Raw FFmpeg encoder options. Visit FFmpeg docs to learn more.

  • Type: Record<string, string>

Properties (type: “vulkan_h264”) Required feature: vk-video

Hardware encoder. Requires GPU that supports Vulkan Video encoding.

bitrate

Encoding bitrate. If not provided, bitrate is calculated based on resolution and framerate. For example at 1080p 30 FPS the average bitrate is 5000 kbit/s and max bitrate is 6250 kbit/s.

Type definitions 

type VulkanH264EncoderBitrate = { averageBitrate: number; maxBitrate: number; } | number;

Properties

averageBitrate

Average bitrate measured in bits/second. Encoder will try to keep the bitrate around the provided average, but may temporarily increase it to the provided max bitrate.

maxBitrate

Max bitrate measured in bits/second.

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 RTP 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";
    preset?: "quality" | "voip" | "lowest_latency";
    sampleRate?: u32;
    forwardErrorCorrection?: boolean;
    expectedPacketLoss?: number;
  }

Configuration for the audio encoder, based on the selected codec.

Properties(type: “opus”)

preset

Audio output encoder preset.

  • Type: "quality" | "voip" | "lowest_latency"
  • Default value: voip
  • Supported values:
    • quality - Recommended for broadcast and high-fidelity applications requiring decoded audio to maintain maximum fidelity to the input signal.
    • voip - Recommended for VoIP and videoconferencing applications, prioritizing listening quality and speech intelligibility.
    • lowest_latency - Recommended only when achieving the lowest possible latency is the highest priority.

sampleRate

Sample rate.

  • Type: u32
  • Default value: 48000
  • Supported values: 8000, 16000, 24000, 48000

forwardErrorCorrection

When enabled, include in-band forward error correction data to protect against packet loss. For more information, visit RFC specification sections 2.1.7 and 4.2.5

  • Type: bool
  • Default value: false

expectedPacketLoss

Expected packet loss expressed as a percentage. This value controls how much redundant data is added to counteract packet loss (only when forward error correction is enabled).

  • Type: u32
  • Default value: 0
  • Supported values: 0-100

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

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