HLS
An output type that allows streaming video and audio from Smelter over HLS. It writes HLS playlist to disk, but user needs to handle serving the files on their own.
Usage
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: 'hls', serverPath: './output.m3u8', video: { encoder: { type: 'ffmpeg_h264', preset: 'ultrafast', }, resolution: { width: 1920, height: 1080, }, }, audio: { channels: 'stereo', encoder: { type: 'aac', }, }, });}void run();Reference
Type definitions
type RegisterHlsOutput = { type: "hls"; serverPath: string; maxPlaylistSize?: number; video?: VideoOptions; audio?: AudioOptions;}Properties
serverPath
Path to the HLS playlist file, specifying its location on the server where Smelter is deployed.
- Type:
string
maxPlaylistSize
Number of segments kept in the playlist. When the limit is reached the oldest segment is removed. If not specified, no segments will removed.
- Type:
number
video
Video track configuration.
- Type:
VideoOptions
audio
Audio track configuration.
- Type:
AudioOptions
VideoOptions
Type definitions
type VideoOptions = { resolution: { width: number; height: number; }; sendEosWhen?: OutputEndCondition; encoder: VideoEncoderOptions;}Parameters of a video source included in the 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.
- Type:
OutputEndCondition
encoder
Video encoder options.
- Type:
VideoEncoderOptions
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: "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:
ultrafastsuperfastveryfastfasterfastmediumslowslowerveryslowplacebo
pixelFormat
Encoder pixel format
- Type:
"yuv420p" | "yuv422p" | "yuv444p" - Default value:
yuv420p - Supported values:
yuv420pyuv422pyuv444p
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 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.
- Type:
OutputEndCondition
encoder
Audio encoder options.
- Type:
AudioEncoderOptions
AudioEncoderOptions
Type definitions
type AudioEncoderOptions = { type: "aac"; sampleRate?: number;}Configuration for the audio encoder, based on the selected codec.
Properties(type: “aac”)
sampleRate
- Type:
number - Default value:
44100 - Supported values:
8000,16000,24000,44100,48000
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.
- MP5 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