add pre-connected audio buffer

examples/voice_agents/basic_agent.py

@@ -71,7 +71,6 @@ async def entrypoint(ctx: JobContext):
     ctx.log_context_fields = {
         "room": ctx.room.name,
     }
-    await ctx.connect()
 
     session = AgentSession(
         vad=ctx.proc.userdata["vad"],
@@ -98,9 +97,6 @@ async def log_usage():
     # shutdown callbacks are triggered when the session is over
     ctx.add_shutdown_callback(log_usage)
 
-    # wait for a participant to join the room
-    await ctx.wait_for_participant()
-
     await session.start(
         agent=MyAgent(),
         room=ctx.room,
@@ -111,6 +107,9 @@ async def log_usage():
         room_output_options=RoomOutputOptions(transcription_enabled=True),
     )
 
+    # join the room when agent is ready
+    await ctx.connect()
+
 
 if __name__ == "__main__":
     cli.run_app(WorkerOptions(entrypoint_fnc=entrypoint, prewarm_fnc=prewarm))

livekit-agents/livekit/agents/voice/room_io/_input.py

@@ -2,16 +2,18 @@
 
 import asyncio
 from abc import ABC, abstractmethod
-from collections.abc import AsyncIterator
+from collections.abc import AsyncIterator, Iterable
 from typing import Generic, TypeVar, Union
 
 from typing_extensions import override
 
 import livekit.rtc as rtc
+from livekit.rtc._proto.track_pb2 import AudioTrackFeature
 
 from ...log import logger
 from ...utils import aio, log_exceptions
 from ..io import AudioInput, VideoInput
+from ._pre_connect_audio import PreConnectAudioHandler
 
 T = TypeVar("T", bound=Union[rtc.AudioFrame, rtc.VideoFrame])
 
@@ -126,14 +128,15 @@ async def _forward_task(
         self,
         old_task: asyncio.Task | None,
         stream: rtc.VideoStream | rtc.AudioStream,
-        track_source: rtc.TrackSource.ValueType,
+        publication: rtc.RemoteTrackPublication,
+        participant: rtc.RemoteParticipant,
     ) -> None:
         if old_task:
             await aio.cancel_and_wait(old_task)
 
         extra = {
-            "participant": self._participant_identity,
-            "source": rtc.TrackSource.Name(track_source),
+            "participant": participant.identity,
+            "source": rtc.TrackSource.Name(publication.source),
         }
         logger.debug("start reading stream", extra=extra)
         async for event in stream:
@@ -172,7 +175,7 @@ def _on_track_available(
         self._stream = self._create_stream(track)
         self._publication = publication
         self._forward_atask = asyncio.create_task(
-            self._forward_task(self._forward_atask, self._stream, publication.source)
+            self._forward_task(self._forward_atask, self._stream, publication, participant)
         )
         return True
 
@@ -202,13 +205,15 @@ def __init__(
         sample_rate: int,
         num_channels: int,
         noise_cancellation: rtc.NoiseCancellationOptions | None,
+        pre_connect_audio_handler: PreConnectAudioHandler | None,
     ) -> None:
         _ParticipantInputStream.__init__(
             self, room=room, track_source=rtc.TrackSource.SOURCE_MICROPHONE
         )
         self._sample_rate = sample_rate
         self._num_channels = num_channels
         self._noise_cancellation = noise_cancellation
+        self._pre_connect_audio_handler = pre_connect_audio_handler
 
     @override
     def _create_stream(self, track: rtc.Track) -> rtc.AudioStream:
@@ -219,6 +224,78 @@ def _create_stream(self, track: rtc.Track) -> rtc.AudioStream:
             noise_cancellation=self._noise_cancellation,
         )
 
+    @override
+    async def _forward_task(
+        self,
+        old_task: asyncio.Task | None,
+        stream: rtc.AudioStream,
+        publication: rtc.RemoteTrackPublication,
+        participant: rtc.RemoteParticipant,
+    ) -> None:
+        if (
+            self._pre_connect_audio_handler
+            and publication.track
+            and AudioTrackFeature.TF_PRECONNECT_BUFFER in publication.audio_features
+        ):
+            try:
+                duration = 0
+                frames = await self._pre_connect_audio_handler.wait_for_data(publication.track.sid)
+                for frame in self._resample_frames(frames):
+                    if self._attached:
+                        await self._data_ch.send(frame)
+                        duration += frame.duration
+                if frames:
+                    logger.debug(
+                        "pre-connect audio buffer pushed",
+                        extra={
+                            "duration": duration,
+                            "track_id": publication.track.sid,
+                            "participant": participant.identity,
+                        },
+                    )
+
+            except asyncio.TimeoutError:
+                logger.warning(
+                    "timeout waiting for pre-connect audio buffer",
+                    extra={
+                        "duration": duration,
+                        "track_id": publication.track.sid,
+                        "participant": participant.identity,
+                    },
+                )
+
+            except Exception as e:
+                logger.error(
+                    "error reading pre-connect audio buffer",
+                    extra={
+                        "error": e,
+                        "track_id": publication.track.sid,
+                        "participant": participant.identity,
+                    },
+                )
+
+        await super()._forward_task(old_task, stream, publication, participant)
+
+    def _resample_frames(self, frames: Iterable[rtc.AudioFrame]) -> Iterable[rtc.AudioFrame]:
+        resampler: rtc.AudioResampler | None = None
+        for frame in frames:
+            if (
+                not resampler
+                and self._sample_rate is not None
+                and frame.sample_rate != self._sample_rate
+            ):
+                resampler = rtc.AudioResampler(
+                    input_rate=frame.sample_rate, output_rate=self._sample_rate
+                )
+
+            if resampler:
+                yield from resampler.push(frame)
+            else:
+                yield frame
+
+        if resampler:
+            yield from resampler.flush()
+
 
 class _ParticipantVideoInputStream(_ParticipantInputStream[rtc.VideoFrame], VideoInput):
     def __init__(self, room: rtc.Room) -> None:

livekit-agents/livekit/agents/voice/room_io/_pre_connect_audio.py

@@ -0,0 +1,129 @@
+import asyncio
+import contextlib
+import time
+from dataclasses import dataclass, field
+
+from livekit import rtc
+
+from ..agent import logger, utils
+
+PRE_CONNECT_AUDIO_BUFFER_STREAM = "lk.agent.pre-connect-audio-buffer"
+
+
+@dataclass
+class _PreConnectAudioBuffer:
+    timestamp: float
+    frames: list[rtc.AudioFrame] = field(default_factory=list)
+
+
+class PreConnectAudioHandler:
+    def __init__(self, room: rtc.Room, *, timeout: float, max_delta_s: float = 1.0):
+        self._room = room
+        self._timeout = timeout
+        self._max_delta_s = max_delta_s
+
+        # track id -> buffer
+        self._buffers: dict[str, asyncio.Future[_PreConnectAudioBuffer]] = {}
+        self._tasks: set[asyncio.Task] = set()
+
+        self._registered_after_connect = False
+
+    def register(self):
+        def _handler(reader: rtc.ByteStreamReader, participant_id: str):
+            task = asyncio.create_task(self._read_audio_task(reader, participant_id))
+            self._tasks.add(task)
+            task.add_done_callback(self._tasks.discard)
+
+            def _on_timeout():
+                logger.warning(
+                    "pre-connect audio received but not completed in time",
+                    extra={"participant": participant_id},
+                )
+                if not task.done():
+                    task.cancel()
+
+            timeout_handle = asyncio.get_event_loop().call_later(self._timeout, _on_timeout)
+            task.add_done_callback(lambda _: timeout_handle.cancel())
+
+        try:
+            if self._room.isconnected():
+                self._registered_after_connect = True
+            self._room.register_byte_stream_handler(PRE_CONNECT_AUDIO_BUFFER_STREAM, _handler)
+        except ValueError:
+            logger.warning(
+                f"pre-connect audio handler for {PRE_CONNECT_AUDIO_BUFFER_STREAM} "
+                "already registered, ignoring"
+            )
+
+    async def aclose(self):
+        self._room.unregister_byte_stream_handler(PRE_CONNECT_AUDIO_BUFFER_STREAM)
+        await utils.aio.cancel_and_wait(*self._tasks)
+
+    async def wait_for_data(self, track_id: str) -> list[rtc.AudioFrame]:
+        # the handler is enabled by default, log a warning only if the buffer is actually used
+        if self._registered_after_connect:
+            logger.warning(
+                "pre-connect audio handler registered after room connection, "
+                "start RoomIO before ctx.connect() to ensure seamless audio buffer.",
+                extra={"track_id": track_id},
+            )
+
+        self._buffers.setdefault(track_id, asyncio.Future())
+        fut = self._buffers[track_id]
+
+        try:
+            if fut.done():
+                buf = fut.result()
+                if (delta := time.time() - buf.timestamp) > self._max_delta_s:
+                    logger.warning(
+                        "pre-connect audio buffer is too old",
+                        extra={"track_id": track_id, "delta_time": delta},
+                    )
+                    return []
+                return buf.frames
+
+            buf = await asyncio.wait_for(fut, self._timeout)
+            return buf.frames
+        finally:
+            self._buffers.pop(track_id)
+
+    @utils.log_exceptions(logger=logger)
+    async def _read_audio_task(self, reader: rtc.ByteStreamReader, participant_id: str):
+        if not (track_id := reader.info.attributes.get("trackId")):
+            logger.warning(
+                "pre-connect audio received but no trackId", extra={"participant": participant_id}
+            )
+            return
+
+        if (fut := self._buffers.get(track_id)) and fut.done():
+            # reset the buffer if it's already set
+            self._buffers.pop(track_id)
+        self._buffers.setdefault(track_id, asyncio.Future())
+        fut = self._buffers[track_id]
+
+        buf = _PreConnectAudioBuffer(timestamp=time.time())
+        try:
+            sample_rate = int(reader.info.attributes["sampleRate"])
+            num_channels = int(reader.info.attributes["channels"])
+
+            duration = 0
+            audio_stream = utils.audio.AudioByteStream(sample_rate, num_channels)
+            async for chunk in reader:
+                for frame in audio_stream.push(chunk):
+                    buf.frames.append(frame)
+                    duration += frame.duration
+
+            for frame in audio_stream.flush():
+                buf.frames.append(frame)
+                duration += frame.duration
+
+            logger.debug(
+                "pre-connect audio received",
+                extra={"duration": duration, "track_id": track_id, "participant": participant_id},
+            )
+
+            with contextlib.suppress(asyncio.InvalidStateError):
+                fut.set_result(buf)
+        except Exception as e:
+            with contextlib.suppress(asyncio.InvalidStateError):
+                fut.set_exception(e)

livekit-agents/livekit/agents/voice/room_io/room_io.py

@@ -19,6 +19,7 @@
 from ..events import AgentStateChangedEvent, UserInputTranscribedEvent
 from ..io import AudioInput, AudioOutput, TextOutput, VideoInput
 from ..transcription import TranscriptSynchronizer
+from ._pre_connect_audio import PreConnectAudioHandler
 
 if TYPE_CHECKING:
     from ..agent_session import AgentSession
@@ -70,6 +71,10 @@ class RoomInputOptions:
     participant_identity: NotGivenOr[str] = NOT_GIVEN
     """The participant to link to. If not provided, link to the first participant.
     Can be overridden by the `participant` argument of RoomIO constructor or `set_participant`."""
+    pre_connect_audio: bool = True
+    """Pre-connect audio enabled or not."""
+    pre_connect_audio_timeout: float = 3.0
+    """The pre-connect audio will be ignored if it doesn't arrive within this time."""
 
 
 @dataclass
@@ -125,8 +130,17 @@ def __init__(
         self._tasks: set[asyncio.Task] = set()
         self._update_state_task: asyncio.Task | None = None
 
+        self._pre_connect_audio_handler: PreConnectAudioHandler | None = None
+
     async def start(self) -> None:
         # -- create inputs --
+        if self._input_options.pre_connect_audio:
+            self._pre_connect_audio_handler = PreConnectAudioHandler(
+                room=self._room,
+                timeout=self._input_options.pre_connect_audio_timeout,
+            )
+            self._pre_connect_audio_handler.register()
+
         if self._input_options.text_enabled:
             try:
                 self._room.register_text_stream_handler(TOPIC_CHAT, self._on_user_text_input)
@@ -144,6 +158,7 @@ async def start(self) -> None:
                 sample_rate=self._input_options.audio_sample_rate,
                 num_channels=self._input_options.audio_num_channels,
                 noise_cancellation=self._input_options.noise_cancellation,
+                pre_connect_audio_handler=self._pre_connect_audio_handler,
             )
 
         # -- create outputs --
@@ -209,6 +224,9 @@ async def aclose(self) -> None:
         if self._init_atask:
             await utils.aio.cancel_and_wait(self._init_atask)
 
+        if self._pre_connect_audio_handler:
+            await self._pre_connect_audio_handler.aclose()
+
         if self._audio_input:
             await self._audio_input.aclose()
         if self._video_input:

livekit-agents/pyproject.toml

@@ -24,7 +24,7 @@ classifiers = [
 ]
 dependencies = [
     "click~=8.1",
-    "livekit>=1.0.6,<2",
+    "livekit>=1.0.7,<2",
     "livekit-api>=1.0.2,<2",
     "livekit-protocol~=1.0",
     "protobuf>=3",