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Jefferson Gonçalves
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Airplay Cli

Unified command-line binary for streaming to AirPlay 1 (RAOP) and AirPlay 2 devices

#cliairplay

Unified AirPlay streaming CLI for Music Assistant. One binary speaks RAOP (AirPlay 1) and AirPlay 2 — both the RAOP-compatible flow and the native HAP flow — replacing the previous cliraop and cliap2 binaries.

Music Assistant spawns one cliairplay process per player and feeds it a single, persistent PCM stream on the process stdin for the whole process lifetime. Seek and next-track flush the live stream in place (cmdpipe ACTION=FLUSH) and re-anchor it with a new ACTION=START — the connection and the input are never re-opened. For synchronized multi-room AirPlay 2 playback it also runs one cliairplay --ptp-daemon per host.

Protocol and architecture detail lives in DESIGN.md; open work in TODO.md.

#Features

  • RAOP (AirPlay 1) via libraop: ALAC (compressed by default), NTP timing, optional RSA payload encryption, legacy Apple TV pairing.
  • AirPlay 2 RAOP-compat: auth-setup + the RAOP flow — the fallback for AirPlay 2 receivers that can neither pair-verify nor pair transiently.
  • AirPlay 2 native: HAP pairing (transient, or pair-verify with stored credentials), encrypted RTSP, binary-plist SETUP, ChaCha20-Poly1305 audio, realtime (type 96) streaming with PTP or NTP timing, and buffered (type 103, RTP over TCP + SETRATEANCHORTIME) auto-selected on receivers that advertise it.
  • Apple MediaRemote metadata: pair-verified Apple targets receive the full now-playing client, playback-state, transport-command, text and artwork sequence used by current Apple senders.
  • PTP timing: an in-process gPTP-dialect grandmaster engine, plus a shared-clock daemon mode (--ptp-daemon/--ptp-shared) for multi-room.
  • Route auto-selection (--protocol auto): the binary picks RAOP vs AirPlay 2, native vs compat, transient vs pair-verify, and PTP vs NTP from the device's mDNS TXT records.
  • Hi-res audio: 24-bit ALAC (44.1 kHz and 48 kHz) on the native realtime stream.
  • Commanded group starts: on every protocol, START_UNIX_MS schedules the first sample to be audible at an exact wall-clock instant, so every member of a sync group is handed the same instant and aligns by construction.

#Usage

# RAOP command-only session (or let --protocol auto decide from --txt):
./bin/cliairplay-macos-arm64 --protocol raop --port 5000 \
  --volume 50 --cmdpipe /tmp/raop-cap 192.168.1.50

# AirPlay 2 native command-only session:
./bin/cliairplay-macos-arm64 --protocol airplay2 --port 7000 \
  --auth <192-hex-credentials> --volume 50 \
  --cmdpipe /tmp/ap2-cap 192.168.1.50

Every streaming protocol requires --cmdpipe; the raw interleaved PCM arrives on the process stdin, which is the single persistent audio input for the whole process lifetime. The format is selected with --samplerate/--bitdepth/--channels (default s16le 44100 stereo). At --bitdepth 24 the input must be s32le; the binary truncates it to the 24-bit samples the ALAC encoder consumes.

#The start contract

START_UNIX_MS=<ms> followed by ACTION=START means: the first sample is audible exactly at that unix-epoch instant for legacy RAOP, RAOP-compatible AirPlay 2, and native AirPlay 2. The first ACTION=START begins the session; a START after an ACTION=FLUSH re-anchors the same live stream to a new instant without reconnecting. A caller can wait for the one-shot [STATUS] audio buffered_ms=<ms> line — emitted once the (new) track has a complete audio packet buffered, or its final short packet reaches EOF — before it commands the start, then send the same start value to every member of a sync group. A START_UNIX_MS of 0 or one the transport cannot honor is corrected forward to the earliest feasible instant (250 ms minimum lead, 200 ms on RAOP) and the [STATUS] started ack always reports the true scheduled instant.

Late joins: wait for the receiver's clock instead of guessing a headroom. A receiver that has just connected cannot seat an anchor yet — it begins probing our PTP clock about a second after connect, on its own schedule, and its servo needs roughly 2.3 s more. That is a property of the device, so any fixed join headroom is either too short or needlessly slow. The binary reports what it measures, from connect:

[STATUS] clock_ready mode=<ptp|ntp> state=<cold|probing|ready|stalled> streak_ms=<u64> exchanges=<u32> ready_in_ms=<u64> ready_at_unix_ms=<u64>

The first line arrives right after [STATUS] connected, whatever the state, so a caller never blocks on a line that will not come; further lines follow only when the state or the projected instant changes, ending at the first state=ready. Plan a join anchor at or after ready_at_unix_ms (valid only when state is probing or ready). mode=ntp means readiness is not measurable for this session — legacy RAOP, or a PTP session that fell back to the NTP responder — so do not wait for it. state=cold can also persist indefinitely for a receiver past the timing engine's 8-peer limit, so keep a timeout. FLUSH and START re-arm the reporting for the next cycle.

state=stalled means our clock has gone unanswered for 5 s — since the last probe if there ever was one, since connect if there was not. That is over four times the slowest first probe measured, so it is not a slow device and not a blip. The receiver is not slaved to us, so it can seat no render position and plays silence however healthy the session looks. Treat it as a failure to report rather than something to wait out; the usual cause is UDP 319/320 not reaching this host from the speaker. It is not final, though: a receiver that starts probing late, or picks up again, reports probing and then ready.

Starting before readiness is still supported and still corrected — see START_JOIN=1 below.

Delivery is not gated on the start time: frames are released up to the receiver's queue depth ahead of each frame's deadline (600 ms by default — see --latency below), itself bounded by the device-reported latencyMax less a 250 ms margin, or by 1.75 s when the receiver reports no window. Receiver buffers therefore fill before a scheduled start and the start cannot underrun.

--latency <ms> overrides the receiver's queue depth on the native AirPlay 2 splice timeline (default 600 ms, maximum 3000 ms — deeper values are clamped with a warning). That depth is the audible latency of every warm seek and track change, so it stays shallow; raise it only for a receiver whose renderer starves at the stock depth and plays silence behind a perfectly healthy session. A window the device reports at stream SETUP still clamps the effective depth, but the 1.75 s stand-in for a window it never reported does not — a caller naming a depth knows the device better than an assumption does.

The effective depth (warm_lead_ms), the render lead and the device window are printed as a [STATUS] latency ... line so the caller can plan group starts from real device capabilities.

#Pairing

  • Apple TV / HomePod (AirPlay 2, PIN): cliairplay --pair-setup <ip> --port 7000 --dacp <id> runs full HomeKit pair-setup — the device shows a PIN, and on success the credentials are printed on stdout (CREDENTIALS: <192 hex chars>). Stream later with --auth <creds> and the same --dacp (the pairing identity is derived from it).
  • Sonos and most third-party AirPlay 2 receivers need no pairing step: the native flow uses transient pairing automatically.
  • Legacy Apple TV (RAOP): cliairplay --pair produces the --secret used by the RAOP flow.

#Multi-room (shared PTP clock)

Only one process per host can bind the privileged PTP ports (UDP 319/320), and every receiver in a sync group must lock to the same grandmaster:

# One per host (root, or CAP_NET_BIND_SERVICE on Linux):
cliairplay --ptp-daemon [--if <ip>] &

# Grant only the privileged-port capability instead of running as root:
sudo setcap cap_net_bind_service=+ep /path/to/cliairplay

# Per device, connect a command-only session. --ptp selects PTP timing (or pass
# --txt and let the SupportsPTP bit do it); --ptp-shared then attaches the
# daemon's clock instead of running an in-process engine.
cliairplay --protocol airplay2 --ptp --ptp-shared --cmdpipe /tmp/cap1 ... <ip1>
cliairplay --protocol airplay2 --ptp --ptp-shared --cmdpipe /tmp/cap2 ... <ip2>

# Wait until both report [STATUS] audio, then send the same start to both:
# START_UNIX_MS=<T>
# ACTION=START

The daemon binds 319/320 once, runs the PTP engine, publishes the elected clock to POSIX shared memory (/cliairplay-ptp), and serves a localhost UDP control channel (127.0.0.1:9010) where streams register their receiver IPs. Streams started with --ptp-shared attach the shm read-only and never bind 319/320; when no live daemon is present they fall back to the in-process engine, identical to a single-device session. MA starts the daemon when the first PTP stream begins and stops it (SIGTERM) when the last one ends.

#Command-line reference

cliairplay [options] --cmdpipe <path> <host_ip>

#Protocol selection

Option Description
--protocol <auto|raop|airplay2|airplay2-compat> Streaming protocol (default: auto, which resolves the full route — RAOP vs AirPlay 2, native vs compat, PTP vs NTP — from the mDNS TXT records in --txt). raop/airplay2 force the protocol; airplay2 picks native vs RAOP-compat on the same terms as auto, and goes native when --txt advertises no features at all (an AirPlay-2-only receiver); airplay2-compat forces the auth-setup + RAOP flow outright.

#Common

Option Description
--port <port> Device RTSP port (default: 5000; AirPlay 2 devices use 7000).
--volume <0-100> Initial volume. Mapped linear-in-dB onto -30..0 dB (the AirPlay ecosystem convention); 0 mutes.
--latency <ms> Receiver queue depth on the native AirPlay 2 splice timeline (default: 600, maximum: 3000). Raise only for receivers whose renderer starves at the stock depth; a device-reported window still clamps it.
--samplerate <rate> Input sample rate (default: 44100).
--bitdepth <16|24> Input bit depth (default: 16). 24 requires the native AirPlay 2 flow and s32le input.
--channels <n> Input channel count (default: 2).
--if <ip> Local interface IP to bind all sockets to (multi-homed hosts).
--dacp <id> DACP ID advertised for remote-control callbacks; also the HAP pairing identity.
--activeremote <id> Active-Remote ID for DACP callbacks.
--cmdpipe <path> Required named pipe for runtime commands and metadata (see below). Audio is not carried here — it is the process stdin.
--udn <name> UDN / instance name used for mDNS.
--debug <0-9> Log verbosity (default: 3).

#RAOP

Option Description
--raw Force uncompressed ALAC frames. Default is compressed ALAC; the binary also falls back to uncompressed when the device's cn field lacks ALAC.
--encrypt Enable RAOP audio-payload encryption (default: clear).
--password <pw> Device password, if the receiver requires one. Used for RAOP digest authentication and as the AirPlay 2 transient pairing secret (DESIGN.md §3a).
--secret <secret> Legacy Apple TV pairing secret (from --pair).
--et <v> --md <v> --am <v> --pk <v> --pw <v> --cn <v> mDNS TXT fields from the receiver's _raop._tcp record (encryption types, metadata types, model, public key, password flag, codec types).

#AirPlay 2

Option Description
--auth <hex> HAP credentials (192 hex chars, from --pair-setup). Selects the native flow with pair-verify.
--ap2-native Force the native flow without credentials (transient pairing), whatever the TXT advertises.
--txt <k=v ...> mDNS TXT records of the _airplay._tcp service; drives route auto-selection.
--publish-ip <ip> Address advertised to devices (timing-peer lists) when it differs from the bind address (Docker bridge, NAT).
--name <name> Device name (native flow).
--hostname <host> Device hostname (native flow).
--ptp Force PTP grandmaster timing (binds UDP 319/320, needs privilege). Default: auto by the SupportsPTP feature bit.
--timing <auto|ptp|ntp> Session timing. auto (default) follows the SupportsPTP bit (or --ptp); ntp forces the NTP responder — the escape for receivers that advertise PTP but never answer a clock probe (e.g. AirPlay-2 video-class TVs). An NTP-timed route never selects the buffered stream.
--buffered Force the buffered stream (type 103, RTP over TCP + PTP anchor) on a native PTP route. Default: auto by the SupportsBufferedAudio feature bit (in-code deny-list for measured-hostile models). CLIAIRPLAY_BUFFERED=0|1 outranks both — kill switch / fleet A/B lever.
--ptp-shared Prefer the shared PTP daemon clock (multi-room): attach the daemon's shm instead of running an engine; fall back to the in-process engine when no daemon is live. Picks the clock source, not the timing mode — pair it with --ptp or a --txt advertising SupportsPTP.
CLIAIRPLAY_PTP_FOLLOW=0|1 (env) Override for following a receiver's own PTP clock instead of serving it ours. Default: auto — a standalone HomePod on HomePod OS 27+ (model=AudioAccessory*, igl=1, no pgid, no tsid, osvers>=27) is followed, because it keeps announcing its own grandmaster for the whole session and never renders audio anchored to the sender's timeline; every other receiver is served our grandmaster as before. 0 never follows (kill switch), 1 follows every receiver. Per receiver: the engine (or the --ptp-daemon) stays grandmaster for the other peers, so mixed multi-room keeps working.

#Utility / daemon modes

Option Description
--check Print cliairplay <version> check and exit (binary validation).
--pair Legacy Apple TV RAOP pairing; produces the --secret for the RAOP flow.
--pair-setup HomeKit pair-setup against <host_ip> (with --port and --dacp): the device shows a PIN, and on success the --auth credentials are printed on stdout. Stream later with the same --dacp.
--ptp-daemon Run only the shared PTP clock: bind UDP 319/320 once, run the engine, publish the elected master to shared memory, serve the control channel until SIGINT/SIGTERM. One per host; needs privilege. Honors --if; takes no host/audio args.

#Runtime commands (--cmdpipe)

Newline-terminated KEY=VALUE lines written to the command pipe control a running stream. The raw PCM audio is not carried here — it is the process stdin, the single persistent audio input for the whole process lifetime.

  • Start / re-anchor: START_UNIX_MS=<unix epoch ms> then ACTION=START. The first START begins the session; a START after an ACTION=FLUSH re-anchors the same live stream (no reconnect). START_UNIX_MS=0 starts as soon as possible. The start contract is VERIFIED: a feasible instant is scheduled exactly, an infeasible one is corrected forward to the earliest feasible instant (audio always flows), and the ack [STATUS] started requested_unix_ms=<ms> at_unix_ms=<ms> always carries the true scheduled instant — the caller compares the two, logs any correction, and re-aligns a sync group by re-STARTing every member at the largest reported instant. START_JOIN=1 marks a late join onto an already-live group timeline; on the first START to a receiver whose clock is still cold the ack is withheld until that clock is measured (up to the anchor, never longer) so it reports an instant the receiver can actually seat. Wait for the ack rather than assuming it is immediate; exactly one arrives per START.
  • ACTION=FLUSH — in-place warm flush for seek/next: it discards the internal ring and drains stdin to empty, acks with [STATUS] flushed, and keeps buffering the next track until the next START. The one-shot [STATUS] audio buffered_ms=<ms> line fires again when the next track's feed has a complete packet buffered, or its final short packet reaches EOF. Every native AirPlay 2 session runs a splice timeline: nothing is sent to the receiver, its queued audio — kept shallow, reported as warm_lead_ms on the [STATUS] latency line — simply plays out, and the next START splices the new track at the commanded instant, filling the gap with encoded silence so the bitstream stays contiguous on one immutable anchor line. Apple receivers require it (any discard, re-anchor or stamp jump makes them emit a short noise burst) and it measured clean on every other receiver class, so it is the default for all of them. On a live splice timeline the ack carries head_unix_ms=<ms>, the audible instant of the frozen delivery head: a commanded start at or behind a member's head is corrected forward to that head plus 250 ms, so anchor every warm START beyond all members' heads and check [STATUS] started at_unix_ms= against what you asked for. The RAOP paths flush the receiver for real (RTSP FLUSH), go quiet until the next START, and ack without the field — as does a flush that arrives before the first START, when there is no head yet.
  • Session lifecycle: ACTION=STANDBY (silence the receiver, keep the connection warm), ACTION=DISCONNECT (end the session).
  • Transport: ACTION=PLAY|PAUSE|STOP.
  • VOLUME=<0-100>.
  • Metadata: TITLE=, ARTIST=, ALBUM=, DURATION=<s>, PROGRESS=<s>, ITEMID=<stable per-track id>, ARTWORKFILE=<local file path or http:// imageproxy URL> (staged; an empty value clears the staging), followed by ACTION=SENDMETA to push the set — metadata and the staged artwork as one bundle; the staged path is consumed by that push. ARTWORK=<local file path or http:// imageproxy URL> pushes artwork on its own, outside a track change.

[STATUS] stopped acknowledges ACTION=STOP once playback has been torn down. STOP is terminal: the audio loop exits, the connection is torn down and the process exits 0, the same shape as ACTION=DISCONNECT. To keep a session reusable, use ACTION=FLUSH (warm seek/next) or ACTION=STANDBY (warm park) — both leave the process and the connection up for a later ACTION=START.

[STATUS] eof means the stdin input ended — the whole feed is done, not just one track.

Status lines are split across both streams: the lifecycle lines on stderr, and the one-shot setup lines (route, capabilities, latency) plus remote-control events on stdout — so a parser has to read both. DESIGN.md §12 lists every line, the stream it uses, and when it fires.

Some receivers (notably Sonos) do not emit audio until they have received metadata; the binary pushes an initial metadata set at the first commanded start, so audio starts regardless of whether the caller ever sends SENDMETA. Pair-verified native Apple sessions additionally mirror these updates over MediaRemote POST /command, including explicit play/pause/stop state. Set CLIAIRPLAY_MRP=0 only to disable that path for comparison or diagnosis. ITEMID keys the now-playing item identity: metadata re-sent under the same id updates the item in place (a tag refinement never presents as a new track), while a new id is a track change that starts at 0:00; without ids, identity falls back to the title/artist/album tuple. Byte-identical artwork keeps its identity even across a track change, redundant ARTWORK= re-sends are ignored, and a PROGRESS= correction — like the pause/resume timeline — rides a lean merge update on MediaRemote sessions, so neither a seek nor a track change on one album redraws the receiver's now-playing screen. Metadata strings are encoded as Unicode binary-plist strings; artwork is signature-checked and capped at 5 MiB. MA imageproxy URLs are normalized to a supported size=512&fmt=jpeg request.

The DMAP path receives the detected image type and original bytes. Before MRP staging, a bounded metadata probe requires image/jpeg, SOI, and a terminal EOI, then extracts dimensions/profile best-effort without decoding or rejecting JPEG internals. No Apple TV byte or profile cutoff is assumed. Baseline/progressive and grayscale/color cases are logged with exact bytes, dimensions, SOF marker, component count, and /command response. A 1 MiB internal staging-allocation guard bounds the copied input and plist; it is not a receiver capability claim. Non-JPEG, over-bound, or incomplete-envelope MRP artwork is omitted without withholding it from DMAP and clears stale state.

tests/mrp_artwork_matrix.py generates the controlled Apple TV size/profile matrix or records/sends any existing JPEG cache path with its SHA-256, profile, dimensions, and full Pillow/libjpeg decode result; see DESIGN.md §8.

#Building

# macOS (native)
make STATIC=1

# Linux cross-compile (example)
make HOST=linux PLATFORM=aarch64 CC=aarch64-linux-gnu-gcc STATIC=1

# Focused native regression tests
make test STATIC=1

Requires the libraop submodule with pre-built static libraries (OpenSSL, libcodecs, libmdns).

#Platforms and CI

CI (.github/workflows/build.yml) cross-builds four targets on every push — linux-x86_64, linux-aarch64, macos-arm64, macos-x86_64 — validates --check on the natively runnable ones, and uploads the binaries as artifacts. Pushing a v* tag additionally runs a release job. The release is published only after the four binaries and SHA256SUMS are ready, at which point GitHub locks its tag and assets. The manually dispatched Auto Release workflow calculates the next patch version, creates its tag, and runs the same release pipeline with generated release notes. After verifying the published assets, CI hashes SHA256SUMS and opens or updates a non-auto-merge PR against the server dev branch with both Dockerfile pins. Same-repository tags and releases use the built-in GITHUB_TOKEN. The private music-assistant-bot GitHub App (slug musicassistant-bot) uses the MUSIC_ASSISTANT_BOT_CLIENT_ID organization variable and MUSIC_ASSISTANT_BOT_PRIVATE_KEY organization secret to mint separate, short-lived tokens: administration read access for this repository's immutable release preflight, and contents/issues/pull requests write access scoped only to the server repository for its pin-update PR.

#Architecture

src/cliairplay.c      CLI entry, route dispatch, playback loops, cmdpipe,
                      --pair-setup and --ptp-daemon modes
src/ap2_client.c      AP2 orchestrator: route resolution, RAOP-compat + native
                      flows, the realtime sender, anchor & pacing
src/ap2_session.c     Protocol-neutral single-stdin flush-and-refill engine
                      (persistent input reader + ring) used by legacy RAOP and
                      both AirPlay 2 flows
src/raop_session.c    Legacy RAOP commit / flush / standby scheduling
src/ap2_hap.c         HAP pair-verify, transient and PIN pair-setup, encrypted
                      RTSP framing (ChaCha20-Poly1305)
src/ap2_io.c          Absolute-deadline socket I/O shared by RTSP and MRP
src/ap2_mrp.c         MediaRemote now-playing sender: /command builders,
                      proto2 + bplist emitters, type-130 DataStream channel
src/ap2_plist.c       Binary plist writer (nested streams array)
src/ap2_bplist.cpp    Binary plist reader (keyed offset-table traversal)
src/ap2_ptp.c         NTP responder + PTP engine (gPTP dialect, BMCA,
                      hold-grandmaster, unicast grants) + daemon loop
src/ap2_ptp_shm.c     Shared PTP clock: POSIX shm double-buffer + control channel
src/alac_ext.cpp      ALAC encoder override with proper 24-bit support
libraop/              Upstream philippe44/libraop (RAOP protocol + crypto)

#Credits and references

This binary follows the trail blazed by Brad Keifer (@bradkeifer), whose earlier cliap2 — the standalone AirPlay 2 streaming client for Music Assistant (adapting OwnTone into a dedicated client) — proved a CLI streamer was viable and directly inspired this unified RAOP + AirPlay 2 binary.

Built on

  • philippe44/libraop — bundled as a submodule and the foundation of the RAOP/AirPlay 1 path: the raopcl client, the cross-platform helpers, the binary-plist code, and the ALAC codec. The cliairplay entry point derives from libraop's cliraop tool (© Philippe44; the original RAOP work © 2004 Shiro Ninomiya).
  • Apple Lossless (ALAC) — audio codec, via libraop's bundled encoder.

Referenced for the AirPlay 2 / HAP / MediaRemote work — studied for wire formats and receiver behaviour to build our own implementation; no source was copied:

  • OwnTone — AirPlay 2 / HAP reference; specifically the RTP sync-packet layout (rtp_common.c) and the gPTP grandmaster dataset that iOS senders announce (libairptp).
  • pyatv — the MediaRemote / DataStream remote-control channel and the protobuf message/field numbers, plus AirPlay 2 protocol detail (pyatv.dev).
  • openairplay/airplay2-receiver — AirPlay 2 receiver-side reverse engineering, and the basis for the local MediaRemote capture rig used to derive the real now-playing sequence.
  • shairport-sync — receiver-side anchor/timing math, used to get the realtime start anchor right.
  • Emanuele Cozzi's AirPlay 2 notes — AirPlay 2 protocol documentation (stream types, channel setup, pairing).

#License

This project as a whole — and the released binaries — are distributed under the GNU General Public License, version 3 (LICENSE). That follows from what the binary contains: the RAOP core descends from the GPL-2.0-or-later raop_play, and the bundled mDNS discovery client (mdnssd) is GPL-3.0.

The sources written for this project (src/) carry per-file SPDX-License-Identifier: Apache-2.0 headers and may be reused under that license on their own. The one exception is src/cliairplay.c, which derives from libraop's cliraop.c and is therefore GPL-2.0-or-later.

Every bundled third-party component, with its copyright notices and license texts, is inventoried in THIRD_PARTY_NOTICES.md, which also ships with every binary release.

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