RTP

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

Usage

To use RTP Output you must register it first. You can do it by sending a request like this:

Example request

POST: /api/output/:output_id/register
Content-Type: application/json

{
  "type": "rtp_stream",
  "transport_protocol": "tcp_server",
  "port": 9003,
  "video": {
    "resolution": { "width": 1280, "height": 720 },
    "encoder": { "type": "ffmpeg_h264" },
    "initial": {
      "root": {
        "type": "view"
      }
    }
  },
  "audio": {
    "encoder": { "type": "opus" },
    "channels": "stereo",
    "initial": {
      "inputs": [{ "input_id": "input_1", "volume": 1 }]
    }
  }
}

See HTTP Routes documentation to learn more about managing outputs.

References

Type definitions

type RtpOutput = {
  type: "rtp_stream";
  port: string | u16;
  ip?: string;
  transport_protocol?: "udp" | "tcp_server";
  video?: VideoOptions;
  audio?: AudioOptions;
}

Properties

port

Depends on the value of the transport_protocol field:

• udp - An UDP port number that RTP packets will be sent to.

• tcp_server - A local TCP port number or a port range that Smelter will listen for incoming connections.l TCP port number or a range of ports that Smelter will listen to for incoming connections.

• Type: string | u16

---

ip

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

• Type: string

---

transport_protocol

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.

---

video

Parameters of a video included in the RTP stream.

• Type: VideoOptions

---

audio

Parameters of an audio included in the RTP stream.

• Type: AudioOptions

VideoOptions

Type definitions

type VideoOptions = {
  resolution: {
    width: u32;
    height: u32;
  };
  send_eos_when?: OutputEndCondition;
  encoder: VideoEncoderOptions;
  initial: { root: Component; };
}

Properties

resolution

Output resolution in pixels.

• Type: { width: u32; height: u32; }

---

send_eos_when

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

---

initial

Root of a component tree/scene that should be rendered for the output. Use update_output request to update this value after registration.

• Type: { root: Component; }

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.

• FFmpeg H264
• FFmpeg VP8
• FFmpeg VP9
• Vulkan H264

AudioOptions

Type definitions

type AudioOptions = {
  mixing_strategy?: "sum_clip" | "sum_scale";
  send_eos_when?: OutputEndCondition;
  encoder: AudioEncoderOptions;
  channels?: "mono" | "stereo";
  initial: { inputs: InputAudio[]; };
}

Properties

mixing_strategy

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.

---

send_eos_when

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

---

channels

Channels configuration

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

initial

Initial audio mixer configuration for output.

• Type: { inputs: InputAudio[]; }

AudioEncoderOptions

Type definitions

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

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

• Opus

InputAudio

Type definitions

type InputAudio = {
  input_id: string;
  volume?: f32;
}

Properties

input_id

ID of an input. It identifies a stream registered using a register input method.

• Type: string

volume

Input volume in range [0, 2]

• Type: f32
• Default value: 1.0
• Supported values: [0, 2]

OutputEndCondition

This type defines when end of an input stream should trigger end of the output stream. Only one of those fields can be set at the time. Unless specified otherwise 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).

Type definitions

type OutputEndCondition = {
  any_of?: string[];
  all_of?: string[];
  any_input?: bool;
  all_inputs?: bool;
}

Properties

any_of

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

• Type: string[]

---

all_of

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

• Type: string[]

---

any_input

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: bool

---

all_inputs

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

• Type: bool