hang

A media library built on top of moq-net for streaming audio and video.

Overview

hang provides media-specific functionality on top of the generic moq-net transport:

• Broadcast - Discoverable collection of tracks with catalog
• Catalog - Metadata describing available tracks, codec info, etc. (updated live)
• Track - Audio/video streams and other data types
• Group - Group of pictures (video) or collection of samples (audio)
• Frame - Timestamp + codec payload pair

Installation

Add to your Cargo.toml:

[dependencies]
hang = "0.1"

Supported Codecs

hang implements most of the WebCodecs specification.

Video:

• H.264 (AVC)
• H.265 (HEVC)
• VP8
• VP9
• AV1

Audio:

• AAC
• Opus

Quick Start

Publishing Video

See rs/hang/examples/video.rs for a complete example of creating a broadcast with a video track, catalog, and publishing frames.

Subscribing to Video

See rs/hang/examples/subscribe.rs for a complete example of subscribing to a broadcast, reading the catalog, and consuming video frames.

Catalog

The catalog is a special track containing JSON metadata about available tracks:

{
  "version": 1,
  "tracks": [
    {
      "name": "video",
      "kind": "video",
      "codec": "avc1.64002a",
      "width": 1920,
      "height": 1080,
      "framerate": 30,
      "bitrate": 5000000
    },
    {
      "name": "audio",
      "kind": "audio",
      "codec": "opus",
      "sampleRate": 48000,
      "channelConfig": "2",
      "bitrate": 128000
    }
  ]
}

The catalog is updated live as tracks are added, removed, or changed.

Frame Container

Each frame in hang consists of a timestamp and codec bitstream payload. See the video example for the Frame struct in action.

CMAF Import

For importing fMP4/CMAF files, see the moq-mux crate. For HLS, see moq-hls.

Grouping

Groups are aligned with natural boundaries:

Video:

• Start with keyframe (I-frame)
• Include dependent frames (P/B-frames)
• Enable joining at group boundaries

Audio:

• Collection of audio packets
• Usually 1 second of audio
• Independent decoding

See the video example for grouping with OrderedProducer.

Prioritization

hang automatically prioritizes:

1. Keyframes - Highest priority (can't decode without them)
2. Recent frames - Higher priority than old frames
3. Audio - Often prioritized over video

This is handled automatically based on frame metadata.

CLI Tool

The moq-cli package provides a command-line tool (binary name: moq-cli):

# Install
cargo install moq-cli

# Publish a video file (remux to MPEG-TS and pipe it in)
ffmpeg -i input.mp4 -c copy -f mpegts - | \
    moq --client-connect https://relay.example.com/anon --broadcast my-stream import ts

# Publish from FFmpeg
ffmpeg -i input.mp4 -f mpegts - | \
    moq --client-connect https://relay.example.com/anon --broadcast my-stream import ts

See moq --help for all options, or FFmpeg documentation.

API Reference

Full API documentation: docs.rs/hang

Key types:

• Broadcast - Media broadcast with catalog
• Catalog - Track metadata
• VideoConfig / AudioConfig - Track configuration
• Frame - Timestamp + codec bitstream
• moq-mux - CMAF/fMP4 import

Protocol Specification

See the hang specification for protocol details.

Next Steps

• Use the moq-net transport layer
• Deploy a relay server
• Read the Concepts guide
• View code examples