AirPlay

RAOP streaming to one or many AirPlay receivers — Apple TV, HomePod, Airport Express, shairport-sync.

Rockbox includes a pure-Rust RAOP (AirPlay 1) implementation. ALAC frames go out over RTP/UDP; RTSP handles session setup. RTCP NTP sync packets are sent roughly every 44 frames so receivers stay in lockstep.

Single receiver

music_dir    = "/path/to/Music"
audio_output = "airplay"
airplay_host = "192.168.1.50"   # IP of the AirPlay receiver
airplay_port = 5000             # optional, default 5000

Multi-room

Fan-out to N receivers simultaneously:

music_dir    = "/path/to/Music"
audio_output = "airplay"

[[airplay_receivers]]
host = "192.168.1.50"   # living room
port = 5000             # optional, default 5000

[[airplay_receivers]]
host = "192.168.1.51"   # bedroom
# port defaults to 5000

[[airplay_receivers]]
host = "192.168.1.52"   # kitchen

All receivers share the same initial_rtptime, so RTP-level synchronisation is within one frame (~8 ms) across the LAN.

Compatible receivers

• Apple TV (any generation supporting AirPlay 1)
• HomePod / HomePod mini
• AirPort Express
• shairport-sync — software AirPlay receiver for Linux, macOS, FreeBSD, OpenWrt
• Most third-party AirPlay-1 speakers

AirPlay 2 is not implemented.

Auto-discovery

Discovered receivers appear in the web UI device picker — click to connect without editing the config. The mDNS service type is _raop._tcp.local..

Debugging

RUST_LOG=rockbox_airplay=debug rockboxd

Common log lines:

DEBUG  rockbox_airplay::rtsp  ANNOUNCE → 192.168.1.50:5000
DEBUG  rockbox_airplay::rtsp  SETUP  → control=53000 timing=53001 server=53002
DEBUG  rockbox_airplay::rtsp  RECORD → 200 OK
DEBUG  rockbox_airplay::rtp   sent 352 frames seq=12345

Limitations

• No password / pairing. AirPlay 1 receivers that require a PIN are not supported.
• No volume sync. Volume changes apply only at the rockboxd side; the receiver’s hardware volume is not adjusted.
• No AirPlay 2. The pairing/encryption stack required for AirPlay 2 is not implemented.

Architecture

The RAOP stack lives in crates/airplay/:

File	Responsibility
alac.rs	ALAC escape/verbatim encoder — 352 stereo S16LE → 1411 bytes
rtp.rs	RTP/UDP packet sender + RTCP NTP sync
rtsp.rs	Synchronous RTSP client: ANNOUNCE → SETUP → RECORD

The C-side sink is firmware/target/hosted/pcm-airplay.c.