RTMP client

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

Usage

To use RTMP Output you need to register it first.

Example request

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

{
  "type": "rtmp_client",
  "url": "https://example.com/rtmp",
  "video": {
    "resolution": { "width": 1280, "height": 720 },
    "encoder": { "type": "ffmpeg_h264" },
    "initial": {
      "root": {
        "type": "view"
      }
    }
  },
  "audio": {
    "encoder": { "type": "aac" },
    "channels": "stereo",
    "initial": {
      "inputs": [{ "input_id": "input_1" }]
    }
  }
}

See HTTP Routes documentation to learn more about managing outputs.

Reference

Type definitions

type RtmpClientOutput = {
  type: "rtmp_client";
  url: string;
  video?: VideoOptions;
  audio?: AudioOptions;
}

Properties

url

RTMP endpoint url.

• Type: string

---

video

Video track configuration.

• Type: VideoOptions

---

audio

Audio track configuration.

• 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";
      preset?:
        | "ultrafast"
        | "superfast"
        | "veryfast"
        | "faster"
        | "fast"
        | "medium"
        | "slow"
        | "slower"
        | "veryslow"
        | "placebo";
      pixel_format?: "yuv420p" | "yuv422p" | "yuv444p";
      ffmpeg_options?: Map<string, string>;
    }
  | {
      type: "vulkan_h264";
      bitrate: { average_bitrate: number; max_bitrate: number; } | number;
    };

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

---

pixel_format

Encoder pixel format

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

---

ffmpeg_options

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

• Type: Map<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 = { average_bitrate: number; max_bitrate: number; } | number;

Properties

average_bitrate

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.

---

max_bitrate

Max bitrate measured in bits/second.

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: "aac";
  sample_rate?: u32;
}

Properties(type: “aac”)

sample_rate

Sample rate.

• Type: u32
• Default value: 44100
• Supported values: 8000, 16000, 24000, 44100, 48000

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