---
url: https://doc.moq.dev/lib/rs/hang.md
description: The media layer
---

# hang

[![crates.io](https://img.shields.io/crates/v/hang)](https://crates.io/crates/hang)
[![docs.rs](https://docs.rs/hang/badge.svg)](https://docs.rs/hang)

The [hang media format](/concept/hang) on top of `moq-net`: a live catalog
describing renditions with WebCodecs-style decoder configs, and containers
that carry a timestamp with every frame.

* **Catalog producer and consumer.** Typed `VideoConfig`, `AudioConfig` and text renditions, the `json` and `binary` data track sections, shared video properties (display size, rotation, flip), stalled hints, cross-broadcast rendition references, and the `archive` entry (timeline track, optional replay path, store URL, and format version). Extend it with your own sections through a lock or `#[serde(flatten)]`, or read unknown sections as raw JSON.
* **Containers.** `legacy`, `cmaf`, and `loc`, decoded for you; unknown kinds pass through untouched.
* **`Ordered`** reads a media track as timestamped frames, reorders groups, and skips ones that fall past your max age.
* **Codecs described**: H.264, H.265, VP8, VP9, AV1, AAC, Opus, PCM.

```bash
cargo add hang
```

`Catalog::<E>::subscribe(&broadcast).await?` opens the uncompressed catalog
track and returns a typed consumer; `consumer.next().await?` yields root updates.
Updates exceeding `catalog::MAX_RENDITIONS` are refused with
`Error::TooManyRenditions`. Media retention uses the public
`container::MAX_AGE` constant.

Producing media is usually done through [`moq-mux`](/lib/rs/moq-mux) (from a
container) or [`moq-video`](/lib/rs/moq-video) and
[`moq-audio`](/lib/rs/moq-audio) (from a device), which build the catalog for
you. Examples:
[`video.rs`](https://github.com/moq-dev/moq/blob/main/rs/hang/examples/video.rs)
and
[`subscribe.rs`](https://github.com/moq-dev/moq/blob/main/rs/hang/examples/subscribe.rs).
API: [docs.rs/hang](https://docs.rs/hang). The TypeScript twin is
[`@moq/hang`](/lib/js/hang).