Fetching Data

Overview

FETCH retrieves historical objects from a track. Unlike SUBSCRIBE (which is a live stream), FETCH returns a bounded set of objects.

Using the CLI

# Fetch data from a track (latest group)
moqtap peek moqt://relay.example.com data live video

# Fetch only the latest object
moqtap peek moqt://relay.example.com data live video latest

# JSON output
moqtap peek moqt://relay.example.com data live video -j

# Raw payload (pipe to file or another tool)
moqtap peek moqt://relay.example.com data live video --raw > output.bin

The peek data command reads the catalog track to understand available content, then subscribes or fetches sample data with auto-detected payload format.

Using the desktop app

1. Enter the namespace and track name
2. Specify the range (start group/object to end group/object)
3. Click Fetch

The FETCH lifecycle

FETCH (sent) → FETCH_OK (received) → objects on fetch stream → stream closes

or:

FETCH (sent) → FETCH_ERROR (received)        # draft-14
FETCH (sent) → REQUEST_ERROR (received)      # draft-17

Viewing fetched objects

Fetched objects arrive on a dedicated unidirectional stream (fetch stream type 0x05 in draft-17). moqtap displays them in order with their group/object IDs and payload content.

Cancelling a FETCH

In draft-14, send FETCH_CANCEL to abort an in-progress fetch. In draft-17, the consolidated request pattern handles cancellation.

Note

Not all relays support FETCH. Check your relay’s documentation for supported features.