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MP4

Node.js Browser (Client) Browser (WASM)

An input type that allows Smelter to read static MP4 files.

Usage

mp4InputExample.tsx
import Smelter from "@swmansion/smelter-node";


async function run() {
  const smelter = new Smelter();
  await smelter.init();
  await smelter.registerInput("example", {
      type: "mp4",
      serverPath: "./input.mp4"
  });
}
void run();

Reference

Type definitions 

type RegisterMp4Input = {
  type: "mp4";
  url?: string;
  serverPath?: string;
  loop?: bool;
  required?: bool;
  offsetMs?: number;
  seekMs?: number;
  decoderMap?: DecoderMap;
  sideChannel?: SideChannel;
}

Parameters for registering an MP4 file as an input.

Properties

url

URL of the MP4 file.

  • Type: string
  • Option availability: Node.js , Browser (WASM)

serverPath

Path to the MP4 file, specifying its location on the server where the Smelter instance is deployed.

  • Type: string
  • Option availability: Node.js

loop

Specifies whether the input should be played in a loop.

  • Type: boolean
  • Default value: false
  • Option availability: Node.js

required

Determines if the input stream is essential for output frame production. If set to true and the stream is delayed, Smelter will postpone output frames until the stream is received.

  • Type: boolean
  • Default value: false
  • Option availability: Node.js

offsetMs

Offset in milliseconds relative to the pipeline start (start request). If unspecified, the stream synchronizes based on the delivery time of the initial frames.

  • Type: number
  • Option availability: Node.js

seekMs

Start playing from a specific timestamp in milliseconds. If loop is enabled, subsequent iterations start from the beginning. The input can also be seeked at runtime through the handle returned from registerInput.

  • Type: number
  • Option availability: Node.js

decoderMap

Assigns which decoder should be used for media encoded with a specific codec.

sideChannel

Enable side channel publishing for this input. The external consumer reads decoded frames / audio from a Unix socket created under SMELTER_SIDE_CHANNEL_SOCKET_DIR.

DecoderMap

Maps codecs to the provided decoders.

Type definitions 

type DecoderMap = {
  h264?: 'ffmpeg_h264' | 'vulkan_h264';
};

Properties

h264

H264 decoder configuration.

  • Type: 'ffmpeg_h264' | 'vulkan_h264'
  • Default value: If available vulkan_h264 will be used, otherwise ffmpeg_h264
  • Supported values:
    • "ffmpeg_h264" - Software H264 decoder based on FFmpeg.
    • "vulkan_h264" (Required feature: gpu-video ) - Hardware decoder. Requires GPU that supports Vulkan Video decoding.

SideChannel

Per-track side channel configuration. See the Side Channel overview for details on how decoded data is exposed and consumed.

Type definition 

type SideChannel = {
  video?: boolean;
  audio?: boolean;
  delayMs?: number;
};

Properties

video

Publish decoded RGBA video frames for this input on the side channel.

  • Type: boolean
  • Default value: false

audio

Publish decoded PCM audio batches for this input on the side channel.

  • Type: boolean
  • Default value: false

delayMs

Side channel delay in milliseconds. Frames are buffered for this duration ahead of when the queue consumes them, so the side-channel subscriber receives them early and has roughly this much time to process before the frame is due.

  • Type: number
  • Default value: 0