MP4

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

Note

MP4 files can contain video and audio tracks encoded with various codecs. This input type supports MP4 video tracks encoded with h264 and audio tracks encoded with AAC.

Caution

If the file contains multiple audio or video tracks, only the first audio track and the first video track will be processed; all additional tracks will be ignored.

Usage

To use MP4 Input you must register it first. You can do it by sending a request like this:

Example request

POST: /api/input/:input_id/register
Content-Type: application/json

{
  "type": "mp4",
  "url": "https://example.com/video.mp4"
}

See HTTP Routes documentation to learn more about managing inputs.

Reference

Type definition

type Mp4Input = {
  type: "mp4";
  url?: string;
  path?: string;
  loop?: bool;
  required?: bool;
  offset_ms?: f64;
  seek_ms?: f64;
  decoder_map?: DecoderMap;
  side_channel?: SideChannel;
}

Parameters for registering an MP4 file as an input.

Note

Exactly one of url or path has to be defined.

Properties

url

URL of the MP4 file.

• Type: string

---

path

Path to the MP4 file.

• Type: string

---

loop

Specifies whether the input should be played in a loop.

• Type: bool
• Default value: false

---

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: bool
• Default value: false

---

offset_ms

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: f64

---

seek_ms

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 with the update input request.

• Type: f64

---

decoder_map

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

• Type: DecoderMap

---

side_channel

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.

• Type: SideChannel

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?: bool;
  audio?: bool;
  delay_ms?: f64;
};

Properties

video

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

• Type: bool
• Default value: false

audio

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

• Type: bool
• Default value: false

delay_ms

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: f64
• Default value: 0