music-assistant-server

1"""Unified AirPlay/RAOP stream session logic for AirPlay devices."""
2
3from __future__ import annotations
4
5import asyncio
6import time
7from collections.abc import AsyncGenerator, Coroutine
8from contextlib import suppress
9from typing import TYPE_CHECKING, Any
10
11from music_assistant_models.enums import ContentType, PlaybackState
12from music_assistant_models.errors import MusicAssistantError, PlayerCommandFailed
13
14from music_assistant.constants import CONF_SYNC_ADJUST
15from music_assistant.controllers.streams.audio_processing import get_media_session_id
16from music_assistant.helpers.ffmpeg import FFMpeg
17
18from .constants import (
19    AIRPLAY_CLOCK_READY_LEAD_MS,
20    AIRPLAY_CLOCK_READY_TIMEOUT_MS,
21    AIRPLAY_COLD_GROUP_START_LEAD_MS,
22    AIRPLAY_GROUP_START_LEAD_MS,
23    AIRPLAY_LATE_JOIN_MIN_HEADROOM_MS,
24    AIRPLAY_LATE_JOIN_RING_MARGIN_SECONDS,
25    AIRPLAY_LATE_JOIN_RING_MAX_BYTES,
26    AIRPLAY_LATE_JOIN_RING_MIN_SECONDS,
27    AIRPLAY_SPLICE_LEAD_MARGIN_MS,
28    AIRPLAY_START_LEAD_MS,
29    ClockReadiness,
30    StreamingProtocol,
31)
32from .helpers import get_final_output_format
33from .stream import AirPlayStream
34
35if TYPE_CHECKING:
36    from music_assistant_models.media_items import AudioFormat
37
38    from music_assistant.models.player import PlayerMedia
39
40    from .player import AirPlayPlayer
41    from .provider import AirPlayProvider
42
43# What each readiness outcome means for the join anchor: a projection only moves
44# it when it clears the join floor, which otherwise carries the anchor alone, so
45# the note says which bound the outcome set. STALLED has no note because it never
46# reaches a join anchor - a stalled joiner is refused the join before that.
47_CLOCK_READINESS_NOTES: dict[ClockReadiness, str] = {
48    ClockReadiness.PROJECTED: "usable in {out:.2f}s; anchoring no earlier than that",
49    ClockReadiness.NOT_APPLICABLE: "runs on NTP timing, so there is none to wait for; "
50    "anchoring on the join floor",
51    ClockReadiness.UNREPORTED: "was not reported within {timeout:.1f}s (a slow device, or a "
52    "receiver that never answered); anchoring on the join floor",
53}
54# A locked clock projects an instant that has already passed - the common case,
55# since only a cold receiver is still probing - so its note reads back in time.
56_CLOCK_LOCKED_NOTE = "became usable {ago:.2f}s ago; anchoring on the join floor"
57
58
59class AirPlayStreamSession:
60    """Stream session (RAOP or AirPlay2) to one or more players."""
61
62    def __init__(
63        self,
64        airplay_provider: AirPlayProvider,
65        sync_clients: list[AirPlayPlayer],
66        pcm_format: AudioFormat,
67        media: PlayerMedia,
68        requested_volume: int | None = None,
69    ) -> None:
70        """
71        Initialize AirPlayStreamSession.
72
73        :param airplay_provider: The AirPlay provider instance.
74        :param sync_clients: List of AirPlay players to stream to.
75        :param pcm_format: PCM format of the input stream.
76        :param media: Queue media that owns the stream session.
77        :param requested_volume: Volume level explicitly requested for this session (an
78            announcement volume), already applied to its members. Omit for a regular
79            stream, which only carries a volume when this output owns it.
80        """
81        assert sync_clients
82        self.prov = airplay_provider
83        self.mass = airplay_provider.mass
84        self.pcm_format = pcm_format
85        self.media = media
86        self.requested_volume = requested_volume
87        self.sync_clients = sync_clients
88        self._audio_source_task: asyncio.Task[None] | None = None
89        self._player_ffmpeg: dict[str, FFMpeg] = {}
90        self._lock = asyncio.Lock()
91        self._ptp_lock = asyncio.Lock()
92        self.start_unix_ms: int = 0
93        self.start_time: float = 0.0
94        self.seconds_streamed: float = 0
95        # Parked in standby: the members stay connected but nothing is fed and
96        # their binaries hold until a START, so only a re-anchor (play_media)
97        # revives them. It outlives the group that parked it, which is why the
98        # session - not the group membership - owns this.
99        self.parked: bool = False
100        # Timing source for the whole session, decided once in start() and applied
101        # identically to every native AirPlay 2 member (and any late joiner) so a
102        # sync group can never mix shared-PTP and NTP members.
103        self.use_shared_ptp: bool = False
104        self._shared_ptp_resolved = False
105        self._ptp_degraded_warning_logged = False
106        # Raw PCM ring buffer for late joiners. When a late joiner arrives we
107        # send this buffer to prime its pipeline so it starts playing quickly
108        # instead of waiting for the full pipeline to fill from scratch.
109        # It must cover the write-head lead - how far the feed runs ahead of the
110        # audible position - because that is exactly the span a joiner's anchor
111        # maps into. The lead is not a constant of the protocol: it is the sum
112        # of every buffer downstream of this counter (see
113        # AIRPLAY_LATE_JOIN_RING_MIN_SECONDS), so it is measured per session and
114        # the ring is grown to match.
115        self._pcm_buffer = bytearray()
116        # Largest write-head lead this session has shown, and the ring size
117        # derived from it.
118        self._peak_lead_seconds: float = 0.0
119        # Raw byte sizes of the PCM actually on the wire. At 24-bit the binary
120        # is fed s32le carriers (bit_depth stays 24 for the ALAC encode), so
121        # sizes MUST come from the content type: bit_depth-derived sizes are
122        # 6 bytes/frame while the wire frames are 8 — slicing or timing the
123        # feed on those boundaries cuts mid-sample (loud noise on a late
124        # joiner's prime) and inflates the position clock by 4/3.
125        bytes_per_sample = {
126            ContentType.PCM_S16LE: 2,
127            ContentType.PCM_S24LE: 3,
128            ContentType.PCM_S32LE: 4,
129            ContentType.PCM_F32LE: 4,
130        }.get(pcm_format.content_type, pcm_format.bit_depth // 8)
131        self._pcm_frame_size = bytes_per_sample * pcm_format.channels
132        self._pcm_byte_rate = self._pcm_frame_size * pcm_format.sample_rate
133        self._pcm_buffer_max = self._ring_bytes_for(0.0)
134        # Bytes still to skip off the head of the live feed for a late joiner
135        # whose anchor lands ahead of the current write head, keyed by player id.
136        self._client_skip_bytes: dict[str, int] = {}
137        # Cumulative bytes fed to the members (absolute stream coordinate of
138        # the write head). Source chunking makes no frame-alignment promise,
139        # so any slice or skip of the live feed must be aligned against THIS
140        # counter — aligning lengths in isolation can still land mid-sample,
141        # which a joiner renders as pure static.
142        self._pcm_total_fed: int = 0
143
144    @property
145    def effective_start_time(self) -> float:
146        """
147        Return the session anchor adjusted for the reference member's clock shift.
148
149        ``start_time`` is the wall-clock anchor set at the last group (re)start.
150        A member's cliairplay can re-anchor its playout LATER after recovering
151        from a PCM starvation, shifting the group's real timeline; that shift is
152        tracked per member. The first sync client is taken as the reference and
153        its accumulated shift is added, so a late joiner maps its first sample to
154        where the group actually plays. Divergent per-member shifts make any
155        single reference imperfect; the current first client is the best
156        available choice and the reference transfers to the new first client when
157        the old one is removed.
158        """
159        if not self.sync_clients:
160            return self.start_time
161        reference_stream = self.sync_clients[0].stream
162        if reference_stream is None:
163            return self.start_time
164        return self.start_time + reference_stream.cumulative_shift_seconds
165
166    async def start(self, audio_source: AsyncGenerator[bytes]) -> None:
167        """
168        Connect every member and anchor synchronized playback.
169
170        Spawns and connects each member's CLI, wires the per-seek ffmpeg into its
171        persistent stdin and starts feeding audio, then commands one shared
172        audible start instant. On any failure the whole session is stopped so the
173        caller can fall back to a cold restart.
174        """
175        ap2_members = sum(1 for p in self.sync_clients if p.protocol == StreamingProtocol.AIRPLAY2)
176        if ap2_members:
177            # Resolve the timing source before calculating the audible anchor so
178            # a bounded daemon-readiness wait cannot consume the setup lead.
179            self.use_shared_ptp = await self._resolve_shared_ptp(ap2_members)
180            self._shared_ptp_resolved = True
181        position_ms = int((self.media.elapsed_time or 0) * 1000)
182        try:
183            async with asyncio.TaskGroup() as task_group:
184                for player in self.sync_clients:
185                    task_group.create_task(
186                        self._member_start_step(
187                            player, "spawn its cli", self._start_client(player, self.use_shared_ptp)
188                        )
189                    )
190            await asyncio.gather(
191                *[
192                    self._member_start_step(
193                        player, "connect to its device", player.stream.wait_for_connection()
194                    )
195                    for player in self.sync_clients
196                    if player.stream
197                ]
198            )
199            # The binary buffers stdin into its ring from process start; feed
200            # audio first and wait for every member to confirm it flowing, then
201            # anchor with a short lead. Readiness is fully event-driven
202            # (connected + audio), so no guessed setup time is needed; the
203            # binary bursts the receiver pre-fill after START.
204            self._audio_source_task = asyncio.create_task(self._audio_streamer(audio_source))
205            await self._wait_members_audio_present()
206            # Members of a group have to agree on one instant, and a freshly
207            # connected receiver needs about a second before it even starts
208            # probing — too late for the binary to raise its own commit floor,
209            # and a first start is the one case it will not correct afterwards.
210            # So a group anchor waits for the receivers to say when they can
211            # play, rather than trusting the lead to have covered it.
212            ready_at_unix_ms = await self._wait_members_clock_ready()
213            await self._start_members(
214                position_ms, self._anchor_start_unix_ms(ready_at_unix_ms=ready_at_unix_ms)
215            )
216        except asyncio.CancelledError:
217            await self.stop()
218            raise
219        except Exception as err:
220            # playback failed to start, cleanup. This runs for every failure. A
221            # per-member one has already been named where it happened, so here
222            # the line says the whole session went down with it; for a failure
223            # no single member owns, it is the only line there is.
224            self.prov.logger.warning(
225                "AirPlay start failed for a session of %d member(s): %s",
226                len(self.sync_clients),
227                err,
228            )
229            await self.stop()
230            # A member can fail for a specific, user-actionable reason (a device
231            # that needs its password configured, for example). That error must
232            # reach the caller intact instead of being flattened into the generic
233            # message; the TaskGroup above nests it inside an exception group.
234            if (specific := _first_music_assistant_error(err)) is not None:
235                raise specific from err
236            raise PlayerCommandFailed("Playback failed to start") from err
237
238    def can_replace(self, sync_clients: list[AirPlayPlayer], pcm_format: AudioFormat) -> bool:
239        """
240        Return whether this live session can absorb a new play_media warm.
241
242        A warm replacement needs the same member set, the same session PCM
243        format and a connected stream on every member; anything else takes the
244        cold path.
245        """
246        if {p.player_id for p in sync_clients} != {p.player_id for p in self.sync_clients}:
247            return False
248        if (
249            pcm_format.sample_rate != self.pcm_format.sample_rate
250            or pcm_format.bit_depth != self.pcm_format.bit_depth
251        ):
252            return False
253        return all(
254            p.stream is not None and p.stream.running and p.stream.connected
255            for p in self.sync_clients
256        )
257
258    async def replace(self, audio_source: AsyncGenerator[bytes], media: PlayerMedia) -> bool:
259        """
260        Warm-replace the playing media with a new source (seek/next-track).
261
262        Stops feeding old audio and kills each member's ffmpeg (never the
263        persistent cli stdin), flushes every member's live stream in place, then
264        feeds a fresh ffmpeg into the same stdin and anchors all members at one
265        shared instant. A group flushes every member and awaits all acks before
266        the shared start. Returns False when anything fails so the caller can
267        fall back to the cold path.
268        """
269        position_ms = int((media.elapsed_time or 0) * 1000)
270        try:
271            # Stop feeding old audio and drop each member's buffered ffmpeg output
272            # before flushing: the binary drains stdin to EAGAIN on FLUSH, so no
273            # bytes may be written between the old ffmpeg dying and the flush ack.
274            # Killing ffmpeg never closes the cli stdin (MA holds the write end),
275            # so the binary keeps its stdin reader alive across the seek.
276            if self._audio_source_task and not self._audio_source_task.done():
277                self._audio_source_task.cancel()
278                with suppress(asyncio.CancelledError):
279                    await self._audio_source_task
280            for player in self.sync_clients:
281                if ffmpeg := self._player_ffmpeg.pop(player.player_id, None):
282                    await ffmpeg.kill()
283            flushed = await asyncio.gather(
284                *[self._flush_member(player) for player in self.sync_clients]
285            )
286            if not all(flushed):
287                raise PlayerCommandFailed("warm flush was not acknowledged")
288            for player in self.sync_clients:
289                await self._start_player_ffmpeg(player, media)
290            self.media = media
291            # The stream position counter and the late-join prime buffer both
292            # describe the OLD timeline; restart them before the new source pumps.
293            self.seconds_streamed = 0
294            self._pcm_total_fed = 0
295            self._pcm_buffer.clear()
296            # The shared START below re-establishes start_time, so the per-client
297            # late-join skip counters and every member's accumulated starvation
298            # shift describe a timeline that no longer exists: reset them.
299            self._client_skip_bytes.clear()
300            self._reset_member_shifts()
301            self._audio_source_task = asyncio.create_task(self._audio_streamer(audio_source))
302            # Anchor only after every member confirms the new audio flowing;
303            # the live connection and clock survive the flush, so a short
304            # re-anchor lead replaces the full setup lead.
305            await self._wait_members_audio_present()
306            await self._start_members(position_ms, self._anchor_start_unix_ms(warm=True))
307        except asyncio.CancelledError:
308            raise
309        except Exception as err:
310            self.prov.logger.warning(
311                "Warm replacement failed (%r); falling back to a cold restart", err
312            )
313            return False
314        return True
315
316    async def standby(self) -> bool:
317        """
318        Park the session: stall every member but keep the connections alive.
319
320        The next play_media (resume or seek) replaces the media warm over the
321        live connections — the same coordinated flush-refill as seek/next.
322        Returns False when any member lacks a running, connected stream or its
323        standby command cannot be delivered so the caller can fall back to a
324        full stop.
325        """
326        if not all(
327            p.stream is not None and p.stream.running and p.stream.connected
328            for p in self.sync_clients
329        ):
330            return False
331        if self._audio_source_task and not self._audio_source_task.done():
332            self._audio_source_task.cancel()
333            with suppress(asyncio.CancelledError):
334                await self._audio_source_task
335        for player in self.sync_clients:
336            if ffmpeg := self._player_ffmpeg.pop(player.player_id, None):
337                await ffmpeg.kill()
338            stream = player.stream
339            assert stream
340            try:
341                command_delivered = await stream.send_cli_command("ACTION=STANDBY")
342            except Exception as err:
343                self.prov.logger.warning(
344                    "Could not park AirPlay player %s: %s", player.player_id, err
345                )
346                return False
347            if not command_delivered:
348                self.prov.logger.warning(
349                    "Could not park AirPlay player %s: standby command was not delivered",
350                    player.player_id,
351                )
352                return False
353            player.set_state_from_stream(state=PlaybackState.PAUSED, stream=stream)
354        # a parked session has no live timeline; the resume re-anchors it
355        self.seconds_streamed = 0
356        self._pcm_total_fed = 0
357        self._pcm_buffer.clear()
358        self._client_skip_bytes.clear()
359        self._reset_member_shifts()
360        self.parked = True
361        return True
362
363    async def stop(self) -> None:
364        """Stop playback and cleanup."""
365        if self._audio_source_task and not self._audio_source_task.done():
366            self._audio_source_task.cancel()
367            with suppress(asyncio.CancelledError):
368                await self._audio_source_task
369        await asyncio.gather(
370            *[self.remove_client(x, reason="session stop") for x in self.sync_clients],
371        )
372
373    async def remove_client(
374        self, airplay_player: AirPlayPlayer, reason: str = "client removed"
375    ) -> None:
376        """
377        Remove a sync client from the session.
378
379        :param airplay_player: The player to remove from the session.
380        :param reason: Short human-readable reason for the removal, used in teardown logs.
381        """
382        async with self._lock:
383            if airplay_player not in self.sync_clients:
384                return
385            self.sync_clients.remove(airplay_player)
386        await self._cleanup_after_removal(airplay_player, reason=reason)
387
388    async def stop_client(
389        self, airplay_player: AirPlayPlayer, reason: str = "stop_client called"
390    ) -> None:
391        """
392        Stop a client's stream and ffmpeg.
393
394        :param airplay_player: The player to stop.
395        :param reason: Short human-readable reason for the teardown, used in debug logs.
396        """
397        self.prov.logger.debug(
398            "AirPlay session teardown: session=%s client=%s reason=%s",
399            id(self),
400            airplay_player.player_id,
401            reason,
402        )
403        self._client_skip_bytes.pop(airplay_player.player_id, None)
404        ffmpeg = self._player_ffmpeg.pop(airplay_player.player_id, None)
405        # note that we use kill instead of graceful close here,
406        # because otherwise it can take a very long time for the process to exit.
407        if ffmpeg and not ffmpeg.closed:
408            await ffmpeg.kill()
409        if airplay_player.stream and airplay_player.stream.session == self:
410            airplay_player.stream.reset_reanchor_shift()
411            await airplay_player.stream.stop(force=True)
412
413    async def add_client(self, airplay_player: AirPlayPlayer) -> None:  # noqa: PLR0915
414        """
415        Add a sync client to the session as a late joiner.
416
417        The joiner cannot honour an anchor in the past — cliairplay makes the
418        first post-START stdin byte audible exactly at the instant it acks and
419        then freezes the anchor, with no catch-up. So the anchor is commanded
420        just past the instant the receiver reports its clock becomes usable (and
421        never inside the join floor), the binary acks the instant it can truly
422        honour, and the stream position due at that instant is derived from the
423        group's effective (shift-adjusted) timeline. Depending on where that
424        position falls relative to the ring buffer the joiner is either primed
425        from the ring tail (position at or behind the write head) or has the
426        leading bytes of the live feed skipped (position ahead of the write
427        head), so its first audible sample lands exactly where the group is
428        playing.
429
430        Timing-source readiness, the receiver's clock projection and the START
431        ack are all awaited without the session lock so the rest of the group
432        keeps being fed meanwhile; all buffer and anchor math stays under the
433        lock so ``seconds_streamed``, the ring buffer and the per-client skip
434        counter stay consistent with the live feed.
435        """
436        await self._resolve_late_joiner_ptp(airplay_player)
437        async with self._lock:
438            if not self._session_is_live():
439                return
440        try:
441            await self._start_client(airplay_player, self.use_shared_ptp)
442            stream = airplay_player.stream
443            assert stream
444            await stream.wait_for_connection()
445            # A receiver starts probing its clock at connect, so how long it
446            # still needs is measurable before any anchor is announced. Waiting
447            # for that projection here — outside the session lock, so the rest
448            # of the group keeps being fed — lets the join anchor on the
449            # device's own readiness instead of a fixed guess.
450            readiness, ready_at_unix_ms = await stream.wait_clock_ready(
451                timeout=AIRPLAY_CLOCK_READY_TIMEOUT_MS / 1000
452            )
453        except asyncio.CancelledError:
454            await self.stop_client(airplay_player, reason="late joiner start cancelled")
455            raise
456        except Exception as err:
457            self.prov.logger.warning(
458                "Late joiner %s: failed to connect pipeline: %s",
459                airplay_player.player_id,
460                err,
461            )
462            await self.stop_client(airplay_player, reason="late joiner connection failed")
463            return
464
465        if readiness is ClockReadiness.STALLED:
466            # The receiver never answered our clock, so it would render silence
467            # for as long as it stayed in the group while every other signal
468            # said it was playing. Better to leave it out: the group keeps
469            # playing and the player stays idle, which is the visible truth.
470            # The binary's own report names the device and the ports to check.
471            self.prov.logger.warning(
472                "Late joiner %s: not adding it to the group - its receiver never answered "
473                "the server's PTP clock, so it would render silence",
474                airplay_player.player_id,
475            )
476            await self.stop_client(airplay_player, reason="receiver clock stalled")
477            return
478
479        pcm_sample_size = self._pcm_byte_rate
480        frame_size = self._pcm_frame_size
481
482        def map_to(anchor_at: float, *, committed: bool) -> tuple[float, float, bytes, int]:
483            """
484            Map an anchor instant onto the live feed (call under the lock).
485
486            Snapshots the ring and derives which stream position the group
487            plays at ``anchor_at``, returning the anchor, the due feed
488            position, the prime slice and the live skip.
489
490            :param anchor_at: Instant at which the joiner's first delivered
491                sample becomes audible.
492            :param committed: True once the binary has acked the instant, which
493                fixes it. A due position the ring can no longer reach is then
494                covered with silence rather than by moving the anchor, because
495                moving an instant the binary already owns would offset the
496                joiner from the group by exactly that much.
497            """
498            # Snapshot the ring, which ends at the write head: it covers the
499            # stream positions [seconds_streamed - len(ring)/rate, seconds_streamed].
500            effective_start_time = self.effective_start_time
501            buffered_pcm = bytes(self._pcm_buffer)
502            due = anchor_at - effective_start_time
503            skip = 0
504            prime_slice = b""
505            if due <= self.seconds_streamed:
506                # The due position is at or behind the write head: prime
507                # the joiner from the ring so the live feed then continues
508                # seamlessly.
509                keep_bytes = int((self.seconds_streamed - due) * pcm_sample_size)
510                # Frame-align the prime START in ABSOLUTE stream
511                # coordinates. The prime must end exactly at the write head
512                # (the live feed continues byte-contiguously from there),
513                # so only the start may move: shift it forward to the next
514                # frame boundary (dropping under one frame, ~23 us).
515                start_abs = self._pcm_total_fed - keep_bytes
516                realign = (frame_size - start_abs % frame_size) % frame_size
517                keep_bytes -= realign
518                if realign:
519                    self.prov.logger.debug(
520                        "Late joiner %s: prime start realigned +%d bytes "
521                        "(write head sits mid-frame)",
522                        airplay_player.player_id,
523                        realign,
524                    )
525                # The ring's own head is frame-aligned only by accident - it is
526                # trimmed on byte overflow - so align it too before measuring
527                # how much of the requested prime it can really serve.
528                ring_head_abs = self._pcm_total_fed - len(buffered_pcm)
529                ring_realign = (frame_size - ring_head_abs % frame_size) % frame_size
530                servable = buffered_pcm[ring_realign:]
531                if keep_bytes > len(servable):
532                    # The due position predates the ring: the write head ran
533                    # further ahead of the audible position than the ring was
534                    # sized for. Those samples are gone, so the join either
535                    # starts a little later (anchor still free to move) or opens
536                    # with that much silence (anchor already acked) - both keep
537                    # the real content on the instant the group plays it, which
538                    # dropping the missing head would not.
539                    missing = keep_bytes - len(servable)
540                    lead = self.seconds_streamed - (time.time() - effective_start_time)
541                    if committed:
542                        # One ring's worth is already far past any real
543                        # shortfall, so it bounds what an implausible ack (one
544                        # mapping back near the session start) can allocate.
545                        pad = min(missing, self._pcm_buffer_max)
546                        prime_slice = bytes(pad) + servable
547                        # A clamped pad cannot reach the due position, so the
548                        # joiner really does end up ahead of the group by the
549                        # remainder. Say which of the two happened.
550                        residual = (missing - pad) / pcm_sample_size
551                        self.prov.logger.warning(
552                            "Late joiner %s: the feed runs %.2fs ahead of the audible "
553                            "position, past the %.2fs of audio kept for a join; opening "
554                            "with %.2fs of silence to cover the missing head. %s Please "
555                            "report this with a debug log.",
556                            airplay_player.player_id,
557                            lead,
558                            len(servable) / pcm_sample_size,
559                            pad / pcm_sample_size,
560                            f"That still leaves it {residual:.2f}s ahead of the group."
561                            if residual
562                            else "The content itself still lands in sync; the joiner is "
563                            "only audible that much late.",
564                        )
565                    else:
566                        due += missing / pcm_sample_size
567                        anchor_at = effective_start_time + due
568                        prime_slice = servable
569                        self.prov.logger.debug(
570                            "Late joiner %s: due position predates the %.2fs ring "
571                            "(feed runs %.2fs ahead); anchoring %.2fs later, on the "
572                            "ring's oldest sample",
573                            airplay_player.player_id,
574                            len(servable) / pcm_sample_size,
575                            lead,
576                            missing / pcm_sample_size,
577                        )
578                elif keep_bytes > 0:
579                    prime_slice = servable[len(servable) - keep_bytes :]
580            else:
581                # The due position is ahead of the write head: skip that
582                # many bytes off the head of the live feed so the joiner's
583                # first delivered byte is the sample due at the anchor.
584                skip = int((due - self.seconds_streamed) * pcm_sample_size)
585                # The first delivered live byte must land on a frame
586                # boundary in ABSOLUTE stream coordinates (round the skip
587                # up, under one frame).
588                first_abs = self._pcm_total_fed + skip
589                skip += (frame_size - first_abs % frame_size) % frame_size
590            return anchor_at, due, prime_slice, skip
591
592        now = time.time()
593        clock_out = ready_at_unix_ms / 1000 - now
594        if readiness is ClockReadiness.PROJECTED and clock_out <= 0:
595            clock_note = _CLOCK_LOCKED_NOTE.format(ago=abs(clock_out))
596        else:
597            clock_note = _CLOCK_READINESS_NOTES.get(readiness, "").format(
598                out=clock_out,
599                timeout=AIRPLAY_CLOCK_READY_TIMEOUT_MS / 1000,
600            )
601        self.prov.logger.debug(
602            "Late joiner %s: receiver clock %s",
603            airplay_player.player_id,
604            clock_note,
605        )
606        async with self._lock:
607            if not self._session_is_live():
608                await self.stop_client(airplay_player, reason="session ended during late join")
609                return
610            # cliairplay makes the first post-START stdin byte audible exactly at
611            # the instant it acks, so the anchor is commanded first and the
612            # content mapped onto the ack afterwards. It sits just past the
613            # instant the receiver's clock becomes usable; the floor is only a
614            # lower bound, and carries the whole anchor when no projection came.
615            min_headroom = AIRPLAY_LATE_JOIN_MIN_HEADROOM_MS / 1000
616            anchor_at = now + min_headroom
617            if ready_at_unix_ms:
618                anchor_at = max(
619                    anchor_at,
620                    (ready_at_unix_ms + AIRPLAY_CLOCK_READY_LEAD_MS) / 1000,
621                )
622            requested_at, fed_pos_due = map_to(anchor_at, committed=False)[:2]
623            start_unix_ms = int(requested_at * 1000)
624            sync_adjust = airplay_player.config.get_value(CONF_SYNC_ADJUST, 0)
625            adjust_ms = sync_adjust if isinstance(sync_adjust, int) else 0
626            position_ms = int(((self.media.elapsed_time or 0) + fed_pos_due) * 1000)
627
628        try:
629            # Anchor the joiner BEFORE feeding the prime: pre-START the binary
630            # only buffers stdin into its bounded ring and sends nothing, so a
631            # prime longer than that ring would wedge that write — and, through
632            # the session lock, stall the whole group's feed. Anchored, the
633            # binary drains the prime as it streams in. The START does not
634            # re-anchor the session timeline (the group keeps playing). Its ack
635            # is awaited WITHOUT the session lock: the binary can hold that ack
636            # until its receiver clock verification resolves, which would
637            # otherwise starve every other member's feed for that whole wait.
638            actual = await stream.start(start_unix_ms + adjust_ms, position_ms, join=True)
639        except asyncio.CancelledError:
640            await self.stop_client(airplay_player, reason="late joiner start cancelled")
641            raise
642        except Exception as err:
643            self.prov.logger.warning(
644                "Late joiner %s: failed to start/prime pipeline: %r",
645                airplay_player.player_id,
646                err,
647            )
648            await self.stop_client(airplay_player, reason="late joiner start/prime failed")
649            return
650
651        try:
652            async with self._lock:
653                if not self._session_is_live():
654                    await self.stop_client(airplay_player, reason="session ended during late join")
655                    return
656                if airplay_player.stream is not stream or not stream.running:
657                    await self.stop_client(
658                        airplay_player, reason="late joiner stopped during start"
659                    )
660                    return
661                # Map the content onto the instant the binary acked — its
662                # verified truth. The ring is re-snapshotted here, so the mapping
663                # covers whatever the group was fed while the ack was outstanding.
664                acked_at = (actual - adjust_ms) / 1000
665                start_at, fed_pos_due, prime, skip_bytes = map_to(acked_at, committed=True)
666                self._client_skip_bytes[airplay_player.player_id] = skip_bytes
667                # An instant that moved carries the content mapped onto it
668                # further into the stream than the position sent with the
669                # command, so progress is reported against the sample that
670                # actually lands on the anchor.
671                acked_position_ms = int(((self.media.elapsed_time or 0) + fed_pos_due) * 1000)
672                if acked_position_ms != position_ms:
673                    stream.rebase_position(acked_position_ms)
674
675                self.prov.logger.debug(
676                    "Late joiner %s: priming %.2fs, skipping %.2fs, stream_pos=%.2fs, "
677                    "fed_pos_due=%.2fs, start_at is %.2fs from now, acked %+d ms off the "
678                    "commanded instant (min_headroom=%.2fs, effective_shift=%.2fs, "
679                    "write_head_lead=%.2fs, peak=%.2fs, ring=%.2fs)",
680                    airplay_player.player_id,
681                    len(prime) / pcm_sample_size,
682                    skip_bytes / pcm_sample_size,
683                    self.seconds_streamed,
684                    fed_pos_due,
685                    start_at - time.time(),
686                    int(acked_at * 1000) - start_unix_ms,
687                    min_headroom,
688                    self.effective_start_time - self.start_time,
689                    self.seconds_streamed - (time.time() - self.effective_start_time),
690                    self._peak_lead_seconds,
691                    self._pcm_buffer_max / pcm_sample_size,
692                )
693
694                if prime:
695                    try:
696                        await self._write_chunk_to_player(airplay_player, prime)
697                    except Exception as err:
698                        self.prov.logger.warning(
699                            "Late joiner %s: failed to start/prime pipeline: %r",
700                            airplay_player.player_id,
701                            err,
702                        )
703                        await self.stop_client(
704                            airplay_player, reason="late joiner start/prime failed"
705                        )
706                        return
707
708                if airplay_player not in self.sync_clients:
709                    self.sync_clients.append(airplay_player)
710                if (
711                    airplay_player.protocol == StreamingProtocol.AIRPLAY2
712                    and not self.use_shared_ptp
713                ):
714                    ap2_members = sum(
715                        1
716                        for player in self.sync_clients
717                        if player.protocol == StreamingProtocol.AIRPLAY2
718                    )
719                    self._warn_degraded_shared_ptp(ap2_members)
720        except asyncio.CancelledError:
721            # the joiner is anchored and audible from here on, so a cancellation
722            # before it is part of the session must still tear it down
723            await self.stop_client(airplay_player, reason="late joiner start cancelled")
724            raise
725
726        self.prov.logger.debug(
727            "Late joiner %s: started after %.2fs",
728            airplay_player.player_id,
729            time.time() - now,
730        )
731
732    def _ring_bytes_for(self, lead_seconds: float) -> int:
733        """
734        Return the late-join ring size that covers a given write-head lead.
735
736        :param lead_seconds: Lead the ring has to span, before margin.
737        """
738        seconds = max(
739            lead_seconds + AIRPLAY_LATE_JOIN_RING_MARGIN_SECONDS,
740            AIRPLAY_LATE_JOIN_RING_MIN_SECONDS,
741        )
742        size = min(int(seconds * self._pcm_byte_rate), AIRPLAY_LATE_JOIN_RING_MAX_BYTES)
743        # Keep it a whole number of frames so it can bound a silence pad without
744        # knocking the prime off its frame boundaries.
745        return size - size % self._pcm_frame_size
746
747    def _observe_write_head_lead(self) -> None:
748        """
749        Track how far the feed runs ahead of the audible position (call under the lock).
750
751        A joiner's anchor maps into exactly this span, so the ring is grown to
752        the largest lead the session has shown. It only ever grows: shrinking it
753        mid-session would discard history a joiner still needs, and the lead is
754        at its largest right after the anchor is placed - the whole downstream
755        pipeline is full by then - so the ring is sized long before any late
756        join can arrive.
757        """
758        if self.start_time <= 0:
759            return  # not anchored yet, so there is no audible position to measure against
760        now = time.time()
761        if now < self.effective_start_time:
762            # Still inside the start lead: everything fed is ahead of an anchor
763            # that has not arrived, which would read as a lead seconds larger
764            # than the pipeline really holds.
765            return
766        lead = self.seconds_streamed - (now - self.effective_start_time)
767        if lead <= self._peak_lead_seconds:
768            return
769        self._peak_lead_seconds = lead
770        self._pcm_buffer_max = self._ring_bytes_for(lead)
771
772    def _session_is_live(self) -> bool:
773        """Return whether the session still plays a joinable timeline (call under the lock)."""
774        if not self.sync_clients:
775            return False
776        reference = self.sync_clients[0]
777        reference_stream = reference.stream
778        if reference_stream is None or not reference_stream.running:
779            return False
780        # A parked (standby) session keeps every member's stream running while
781        # its timeline is gone - the anchor is stale and nothing is being fed -
782        # so only a member that is actually playing can absorb a joiner.
783        return reference.playback_state == PlaybackState.PLAYING
784
785    async def _resolve_shared_ptp(self, ap2_members: int | None = None) -> bool:
786        """
787        Decide, once per session, whether members attach to the shared PTP daemon.
788
789        The decision is session-wide and gated on the daemon actually being ready
790        (bound to 319/320 with its control channel open), not merely spawned, so a
791        group start cannot race the daemon and end up mixing PTP and NTP members.
792
793        :param ap2_members: Number of native AirPlay 2 members that will use the
794            decision. Defaults to the current session members.
795        :return: True if every native AirPlay 2 member should use the shared PTP
796            clock; False to degrade the whole session consistently (no member
797            attaches to the daemon).
798        """
799        if ap2_members is None:
800            ap2_members = sum(
801                1 for p in self.sync_clients if p.protocol == StreamingProtocol.AIRPLAY2
802            )
803        if not ap2_members:
804            return False
805        if await self.prov.wait_ptp_daemon_ready():
806            return True
807        # Daemon not ready: keep the group coherent by attaching no one to the
808        # shared clock. A lone native AP2 player can still self-bind its own PTP
809        # with no partner to drift against; only a real multi-room group loses
810        # tight sync, so warn just for that case.
811        self._warn_degraded_shared_ptp(ap2_members)
812        return False
813
814    async def _resolve_late_joiner_ptp(self, airplay_player: AirPlayPlayer) -> None:
815        """Resolve the session timing source before its first late AirPlay 2 join."""
816        if airplay_player.protocol != StreamingProtocol.AIRPLAY2:
817            return
818        async with self._ptp_lock:
819            if self._shared_ptp_resolved:
820                return
821            async with self._lock:
822                ap2_members = sum(
823                    1
824                    for player in self.sync_clients
825                    if player.protocol == StreamingProtocol.AIRPLAY2
826                ) + (airplay_player not in self.sync_clients)
827            self.use_shared_ptp = await self._resolve_shared_ptp(ap2_members)
828            self._shared_ptp_resolved = True
829
830    def _warn_degraded_shared_ptp(self, ap2_members: int) -> None:
831        """Warn once when multiple AirPlay 2 members cannot share the PTP clock."""
832        if ap2_members <= 1 or self._ptp_degraded_warning_logged:
833            return
834        self._ptp_degraded_warning_logged = True
835        self.prov.logger.warning(
836            "Shared PTP clock daemon not ready - native AirPlay 2 multi-room sync "
837            "for this group of %d players is degraded and members may drift. The "
838            "server likely cannot bind the privileged PTP ports (UDP 319/320); "
839            "running without root or CAP_NET_BIND_SERVICE is the common cause.",
840            ap2_members,
841        )
842
843    async def _cleanup_after_removal(
844        self, airplay_player: AirPlayPlayer, reason: str = "client removed"
845    ) -> None:
846        """
847        Clean up processes and state after a client has been removed from sync_clients.
848
849        :param airplay_player: The player whose processes should be stopped.
850        :param reason: Short human-readable reason, forwarded to stop_client for logging.
851        """
852        stream = airplay_player.stream
853        if stream is not None and stream.session != self:
854            stream = None
855        await self.stop_client(airplay_player, reason=reason)
856        # Only set IDLE if the player's stream still belongs to this session,
857        # otherwise a re-add to a new session may have already set a new state.
858        if stream is not None:
859            airplay_player.set_state_from_stream(PlaybackState.IDLE, stream=stream)
860        # Re-check sync_clients under the lock to avoid racing with add_client.
861        async with self._lock:
862            should_stop = not self.sync_clients
863        if should_stop:
864            await self.stop()
865
866    async def _audio_streamer(self, audio_source: AsyncGenerator[bytes]) -> None:
867        """Stream audio to all players."""
868        stream_error: BaseException | None = None
869        try:
870            async for chunk in audio_source:
871                if not self.sync_clients:
872                    break
873
874                has_running_clients = await self._write_chunk_to_all_players(chunk)
875                if not has_running_clients:
876                    self.prov.logger.debug("No running clients remaining, stopping audio streamer")
877                    break
878        except asyncio.CancelledError:
879            self.prov.logger.debug("Audio streamer cancelled after %.1fs", self.seconds_streamed)
880            raise
881        except Exception as err:
882            stream_error = err
883            self.prov.logger.error(
884                "Audio source error after %.1fs of streaming: %s",
885                self.seconds_streamed,
886                err,
887                exc_info=err,
888            )
889        finally:
890            if stream_error:
891                self.prov.logger.warning(
892                    "Stream ended prematurely due to error - notifying players"
893                )
894        async with self._lock:
895            await asyncio.gather(
896                *[
897                    self._write_eof_to_player(x)
898                    for x in self.sync_clients
899                    if x.stream and x.stream.running
900                ],
901                return_exceptions=True,
902            )
903
904    async def _write_chunk_to_all_players(self, chunk: bytes) -> bool:
905        """
906        Write a chunk to all connected players.
907
908        :return: True if there are still running clients, False otherwise.
909        """
910        async with self._lock:
911            sync_clients = [x for x in self.sync_clients if x.stream and x.stream.running]
912            if not sync_clients:
913                return False
914
915            # Update seconds_streamed and ring buffer under the lock so
916            # add_client always reads consistent values.
917            self.seconds_streamed += len(chunk) / self._pcm_byte_rate
918            self._pcm_total_fed += len(chunk)
919            self._observe_write_head_lead()
920            self._pcm_buffer.extend(chunk)
921            overflow = len(self._pcm_buffer) - self._pcm_buffer_max
922            if overflow > 0:
923                del self._pcm_buffer[:overflow]
924
925            # Write chunk to all players
926            write_tasks = [self._write_chunk_to_player(x, chunk) for x in sync_clients if x.stream]
927            results = await asyncio.gather(*write_tasks, return_exceptions=True)
928
929            # Check for write errors or timeouts
930            players_to_remove: list[tuple[AirPlayPlayer, str]] = []
931            for i, result in enumerate(results):
932                if i >= len(sync_clients):
933                    continue
934                player = sync_clients[i]
935
936                if isinstance(result, TimeoutError):
937                    self.prov.logger.warning(
938                        "Removing player %s from session: stopped reading data (write timeout)",
939                        player.player_id,
940                    )
941                    players_to_remove.append((player, "audio write timeout"))
942                elif isinstance(result, Exception):
943                    self.prov.logger.warning(
944                        "Removing player %s from session due to write error: %s",
945                        player.player_id,
946                        result,
947                    )
948                    players_to_remove.append((player, f"audio write error: {result}"))
949
950            # Remove failed players from sync_clients immediately under the lock
951            # so they are excluded from future write cycles. Only defer process
952            # cleanup (_cleanup_after_removal) — this prevents fire-and-forget
953            # remove_client calls from racing with a subsequent add_client when
954            # a player is being moved between groups.
955            for player, removal_reason in players_to_remove:
956                if player in self.sync_clients:
957                    self.sync_clients.remove(player)
958                self.mass.create_task(self._cleanup_after_removal(player, reason=removal_reason))
959
960            remaining_clients = len(sync_clients) - len(players_to_remove)
961            return remaining_clients > 0
962
963    async def _write_chunk_to_player(self, airplay_player: AirPlayPlayer, chunk: bytes) -> None:
964        """Write audio chunk to a player's ffmpeg process."""
965        player_id = airplay_player.player_id
966        # Drain any pending late-join skip first: a joiner anchored ahead of the
967        # write head must drop that many leading bytes of the live feed so its
968        # first delivered byte is the sample due at its anchor.
969        if skip := self._client_skip_bytes.get(player_id, 0):
970            if skip >= len(chunk):
971                self._client_skip_bytes[player_id] = skip - len(chunk)
972                return
973            chunk = chunk[skip:]
974            self._client_skip_bytes[player_id] = 0
975        if ffmpeg := self._player_ffmpeg.get(player_id):
976            if ffmpeg.closed:
977                return
978            await asyncio.wait_for(ffmpeg.write(chunk), timeout=35.0)
979
980    async def _write_eof_to_player(self, airplay_player: AirPlayPlayer) -> None:
981        """Write EOF to a specific player."""
982        if ffmpeg := self._player_ffmpeg.pop(airplay_player.player_id, None):
983            await ffmpeg.write_eof()
984            await ffmpeg.wait_with_timeout(30)
985            if airplay_player.stream:
986                await airplay_player.stream.write_audio_eof()
987
988    async def _member_start_step(
989        self, airplay_player: AirPlayPlayer, step: str, awaitable: Coroutine[Any, Any, None]
990    ) -> None:
991        """
992        Run one per-member step of a group start, naming the member if it fails.
993
994        A group start fans its members out over a task group and a gather, both
995        of which collapse into a single exception at the caller - so with five
996        speakers connecting, nothing in the log says which one failed. That,
997        with whatever reason its binary reported, is the whole diagnostic.
998
999        :param airplay_player: The member the step belongs to.
1000        :param step: What the member was doing, for the failure message.
1001        :param awaitable: The step to run.
1002        """
1003        try:
1004            await awaitable
1005        except asyncio.CancelledError:
1006            raise
1007        except Exception as err:
1008            self.prov.logger.warning(
1009                "AirPlay group start: %s failed to %s: %s",
1010                airplay_player.display_name,
1011                step,
1012                err,
1013            )
1014            raise
1015
1016    async def _start_client(self, airplay_player: AirPlayPlayer, use_shared_ptp: bool) -> None:
1017        """
1018        Connect a CLI process and start its ffmpeg for a single client.
1019
1020        :param airplay_player: The player to start streaming to.
1021        :param use_shared_ptp: The session-wide shared-PTP decision applied to
1022            this member so the whole group shares one timing source.
1023        """
1024        # joining a session supersedes any pending automatic group re-join
1025        airplay_player.cancel_group_rejoin()
1026        airplay_player.release_foreign_mute_latch()
1027        if airplay_player.stream and airplay_player.stream.running:
1028            await airplay_player.stream.stop()
1029        stream_pcm_format = airplay_player.get_stream_pcm_format(self.pcm_format)
1030        airplay_player.stream = AirPlayStream(airplay_player, pcm_format=stream_pcm_format)
1031        airplay_player.stream.session = self
1032        await airplay_player.stream.connect(use_shared_ptp)
1033        await self._start_player_ffmpeg(airplay_player, self.media)
1034
1035    def _anchor_start_unix_ms(self, *, warm: bool = False, ready_at_unix_ms: int = 0) -> int:
1036        """
1037        Return the shared audible-start instant for a readiness-confirmed start.
1038
1039        :param warm: True for a warm re-start over live connections (seek/next/
1040            resume-from-park). Members on the splice timeline report a
1041            minimum warm lead — their queued audio plays out before the new
1042            content can begin — and the shared anchor must sit beyond the
1043            largest member value so every member splices at the same instant.
1044        :param ready_at_unix_ms: Latest instant at which a member's receiver
1045            clock becomes usable, as the binaries reported it. The anchor never
1046            lands before it. 0 when no member reported a projection, leaving the
1047            lead below as the whole anchor.
1048        """
1049        if len(self.sync_clients) == 1:
1050            lead_ms = AIRPLAY_START_LEAD_MS
1051        elif warm:
1052            lead_ms = AIRPLAY_GROUP_START_LEAD_MS
1053        else:
1054            # Cold group start: cover the members' receiver-side clock
1055            # acquisition (see AIRPLAY_COLD_GROUP_START_LEAD_MS).
1056            lead_ms = AIRPLAY_COLD_GROUP_START_LEAD_MS
1057        anchor = int(time.time() * 1000) + lead_ms
1058        if ready_at_unix_ms:
1059            anchor = max(anchor, ready_at_unix_ms + AIRPLAY_CLOCK_READY_LEAD_MS)
1060        if not warm:
1061            return anchor
1062        # Splice-timeline members honor the commanded instant only when that
1063        # instant (plus their sync_adjust) lands beyond their queued audio.
1064        # A NEGATIVE sync_adjust moves a member's commanded instant earlier,
1065        # eating into the lead, so it must be added to that member's
1066        # requirement — otherwise the first round can never succeed for that
1067        # member and every group start pays a corrective round.
1068        member_requirement = 0
1069        for player in self.sync_clients:
1070            stream = player.stream
1071            if stream is None or stream.warm_lead_ms <= 0:
1072                continue
1073            sync_adjust = player.config.get_value(CONF_SYNC_ADJUST, 0)
1074            adjust_ms = sync_adjust if isinstance(sync_adjust, int) else 0
1075            member_requirement = max(member_requirement, stream.warm_lead_ms - min(0, adjust_ms))
1076        if member_requirement > 0:
1077            anchor = max(
1078                anchor,
1079                int(time.time() * 1000) + member_requirement + AIRPLAY_SPLICE_LEAD_MARGIN_MS,
1080            )
1081        for player in self.sync_clients:
1082            stream = player.stream
1083            if stream is None or stream.flushed_head_unix_ms <= 0:
1084                continue
1085            sync_adjust = player.config.get_value(CONF_SYNC_ADJUST, 0)
1086            adjust_ms = sync_adjust if isinstance(sync_adjust, int) else 0
1087            # The member's commanded instant is anchor + adjust; it must clear
1088            # the member's frozen head with margin for the command round-trip.
1089            anchor = max(
1090                anchor,
1091                stream.flushed_head_unix_ms - adjust_ms + AIRPLAY_SPLICE_LEAD_MARGIN_MS,
1092            )
1093        return anchor
1094
1095    async def _wait_members_audio_present(self) -> None:
1096        """Wait until every member's binary reports the new audio flowing."""
1097        members = [(p, p.stream) for p in self.sync_clients if p.stream]
1098        results = await asyncio.gather(*[stream.wait_audio_present() for _, stream in members])
1099        if all(results):
1100            return
1101        # Name the members that never reported audio: they are what has to be
1102        # looked at, and the group start below is abandoned for all of them.
1103        silent = [
1104            player.display_name
1105            for (player, _), present in zip(members, results, strict=True)
1106            if not present
1107        ]
1108        raise PlayerCommandFailed(f"audio feed was not confirmed by {', '.join(silent)}")
1109
1110    async def _wait_members_clock_ready(self) -> int:
1111        """
1112        Return the latest receiver-clock readiness any member reported.
1113
1114        Members that report nothing contribute no instant to the maximum; the
1115        caller anchors those on its lead alone.
1116
1117        :return: Unix epoch ms of the latest projection any member reported, or 0
1118            when there is nothing to wait for — a receiver on NTP timing, or one
1119            that never answered. The caller then anchors on its lead alone.
1120        """
1121        # A solo start waits for the projection too: a receiver that has not
1122        # seated its clock renders silence at an anchor it cannot honor, and
1123        # enough of them need that time (WiiM, Edifier) that no start may assume
1124        # otherwise. It costs a warm clock nothing - the binary reports it ready
1125        # with a past instant right after connect - and a cold one anchors just
1126        # past its own projection instead of being corrected there by the binary
1127        # afterwards: the same instant, planned rather than repaired, with the
1128        # readiness lead's slack on top.
1129        results = await asyncio.gather(
1130            *[
1131                p.stream.wait_clock_ready(timeout=AIRPLAY_CLOCK_READY_TIMEOUT_MS / 1000)
1132                for p in self.sync_clients
1133                if p.stream
1134            ]
1135        )
1136        ready_at_unix_ms = max(
1137            (at for readiness, at in results if readiness is ClockReadiness.PROJECTED), default=0
1138        )
1139        # A group start does not drop a member that stalled - the rest of the
1140        # group would still be started, and the member is already warned about
1141        # by name, with the ports to check, where the binary reported it. Say
1142        # which outcomes were seen so the anchor decision is readable.
1143        unprojected = [
1144            readiness for readiness, _ in results if readiness is not ClockReadiness.PROJECTED
1145        ]
1146        if unprojected:
1147            self.prov.logger.debug(
1148                "AirPlay start: %d of %d member(s) reported no receiver clock projection (%s); "
1149                "anchoring those on the start lead alone",
1150                len(unprojected),
1151                len(results),
1152                ", ".join(sorted({readiness.value for readiness in unprojected})),
1153            )
1154        return ready_at_unix_ms
1155
1156    async def _start_members(self, position_ms: int, start_unix_ms: int) -> None:
1157        """
1158        Anchor every member's playback at one shared audible instant.
1159
1160        The binaries verify the instant: each ack carries the TRUE scheduled
1161        instant (an infeasible one is corrected forward, never silently
1162        misplaced). When any member was corrected, every member is re-STARTed
1163        at the largest reported instant so the group converges on one shared
1164        instant; the recorded session anchor is always the verified truth.
1165        A solo member is never re-STARTed: its corrected instant is simply
1166        adopted as the anchor, since there is no partner to converge with.
1167
1168        :param position_ms: Media position mapped to the first sample of the anchor.
1169        :param start_unix_ms: Shared audible-start instant in unix epoch ms.
1170        """
1171        target_ms = start_unix_ms
1172        corrected_ms = start_unix_ms
1173        for _ in range(4):
1174            member_tasks: list[tuple[int, asyncio.Task[int]]] = []
1175            async with asyncio.TaskGroup() as task_group:
1176                for player in self.sync_clients:
1177                    stream = player.stream
1178                    if stream is None:
1179                        continue
1180                    sync_adjust = player.config.get_value(CONF_SYNC_ADJUST, 0)
1181                    adjust_ms = sync_adjust if isinstance(sync_adjust, int) else 0
1182                    member_tasks.append(
1183                        (
1184                            adjust_ms,
1185                            task_group.create_task(
1186                                stream.start(target_ms + adjust_ms, position_ms)
1187                            ),
1188                        )
1189                    )
1190            corrected_ms = target_ms
1191            for adjust_ms, task in member_tasks:
1192                corrected_ms = max(corrected_ms, task.result() - adjust_ms)
1193            if corrected_ms <= target_ms + 2:
1194                break
1195            if len(member_tasks) == 1:
1196                # A lone member has no partner to converge with and its binary
1197                # already scheduled the corrected instant exactly, so adopt that
1198                # as the anchor. Re-STARTing it only does damage: the command
1199                # re-bases reported position on the raw position_ms (start()
1200                # writes that base unconditionally), throwing away the
1201                # correction the anchor already folded into it, and if the
1202                # second ack times out the session records an instant the
1203                # binary never played on.
1204                target_ms = corrected_ms
1205                break
1206            self.prov.logger.warning(
1207                "AirPlay group start corrected: a member could not honor %d, "
1208                "re-anchoring all members at %d (+%d ms)",
1209                target_ms,
1210                corrected_ms,
1211                corrected_ms - target_ms,
1212            )
1213            # The corrected instant already carries the binary's own
1214            # command-latency slack; the extra margin covers fanning the
1215            # retry out to every member so the next round lands.
1216            target_ms = corrected_ms + AIRPLAY_SPLICE_LEAD_MARGIN_MS
1217        else:
1218            # No round landed, so the members sit on the instants they last
1219            # reported, not on the retry that was about to be commanded. The
1220            # anchor has to record where they actually are, or every later
1221            # joiner maps against a timeline the group never played.
1222            target_ms = corrected_ms
1223            self.prov.logger.error(
1224                "AirPlay group start did not converge after 4 rounds "
1225                "(members last reported %d) - they may be audibly out of sync; "
1226                "please report this with a debug log",
1227                target_ms,
1228            )
1229        self.start_unix_ms = target_ms
1230        self.start_time = target_ms / 1000
1231        # the only place a session (re)gains a live timeline, so any park ends here
1232        self.parked = False
1233
1234    async def _flush_member(self, player: AirPlayPlayer) -> bool:
1235        """Flush one member's live stream in place and report the binary's ack."""
1236        stream = player.stream
1237        if stream is None:
1238            return False
1239        return await stream.flush()
1240
1241    def _reset_member_shifts(self) -> None:
1242        """Zero every member's accumulated starvation shift for a fresh anchor."""
1243        for player in self.sync_clients:
1244            if player.stream is not None:
1245                player.stream.reset_reanchor_shift()
1246
1247    async def _start_player_ffmpeg(self, player: AirPlayPlayer, media: PlayerMedia) -> None:
1248        """
1249        Start the per-seek ffmpeg feeding a member's persistent cli stdin.
1250
1251        Retires any ffmpeg still tracked for the player and wires a fresh one to
1252        the same cli stdin fd. Killing ffmpeg never closes cli stdin (MA holds
1253        the write end via its process transport), so the binary's stdin reader
1254        survives a warm seek.
1255
1256        :param player: The member whose ffmpeg is (re)started.
1257        :param media: Media whose queue/session identify the output plan.
1258        """
1259        if ffmpeg := self._player_ffmpeg.pop(player.player_id, None):
1260            await ffmpeg.close()
1261        stream = player.stream
1262        assert stream
1263        handoff_format = stream.pcm_format
1264        output_plan = self.mass.streams.audio.get_player_output_plan(
1265            player.player_id,
1266            input_format=self.pcm_format,
1267            output_format=get_final_output_format(handoff_format),
1268            handoff_format=handoff_format,
1269            queue_id=media.source_id,
1270            session_id=get_media_session_id(media),
1271        )
1272        cli_proc = stream._cli_proc
1273        assert cli_proc
1274        assert cli_proc.proc
1275        assert cli_proc.proc.stdin
1276        stdin_transport = cli_proc.proc.stdin.transport
1277        audio_output: str | int = stdin_transport.get_extra_info("pipe").fileno()
1278        ffmpeg = FFMpeg(
1279            audio_input="-",
1280            input_format=self.pcm_format,
1281            output_format=handoff_format,
1282            filter_params=output_plan.filter_params,
1283            audio_output=audio_output,
1284        )
1285        await ffmpeg.start()
1286        self._player_ffmpeg[player.player_id] = ffmpeg
1287
1288
1289def _first_music_assistant_error(err: BaseException) -> MusicAssistantError | None:
1290    """
1291    Return the first MusicAssistantError inside an error or (nested) exception group.
1292
1293    :param err: The error to inspect.
1294    """
1295    if isinstance(err, MusicAssistantError):
1296        return err
1297    if isinstance(err, BaseExceptionGroup):
1298        for nested in err.exceptions:
1299            if (found := _first_music_assistant_error(nested)) is not None:
1300                return found
1301    return None
1302