Refactoring the sound plugin to use ffmpeg as a stream converter.

platypush/backend/http/app/routes/plugins/sound/__init__.py

@@ -1,74 +0,0 @@
-import os
-import tempfile
-
-from flask import Response, Blueprint, request
-
-from platypush.backend.http.app import template_folder
-from platypush.backend.http.app.utils import authenticate, send_request
-
-sound = Blueprint('sound', __name__, template_folder=template_folder)
-
-# Declare routes list
-__routes__ = [
-    sound,
-]
-
-
-# Generates the .wav file header for a given set of samples and specs
-# noinspection PyRedundantParentheses
-def gen_header(sample_rate, sample_width, channels):
-    datasize = int(2000 * 1e6)                                               # Arbitrary data size for streaming
-    o = bytes("RIFF", ' ascii')                                               # (4byte) Marks file as RIFF
-    o += (datasize + 36).to_bytes(4, 'little')                               # (4byte) File size in bytes
-    o += bytes("WAVE", 'ascii')                                              # (4byte) File type
-    o += bytes("fmt ", 'ascii')                                              # (4byte) Format Chunk Marker
-    o += (16).to_bytes(4, 'little')                                          # (4byte) Length of above format data
-    o += (1).to_bytes(2, 'little')                                           # (2byte) Format type (1 - PCM)
-    o += channels.to_bytes(2, 'little')                                      # (2byte)
-    o += sample_rate.to_bytes(4,  'little')                                  # (4byte)
-    o += (sample_rate * channels * sample_width // 8).to_bytes(4, 'little')  # (4byte)
-    o += (channels * sample_width // 8).to_bytes(2, 'little')                # (2byte)
-    o += sample_width.to_bytes(2, 'little')                                  # (2byte)
-    o += bytes("data", 'ascii')                                              # (4byte) Data Chunk Marker
-    o += datasize.to_bytes(4, 'little')                                      # (4byte) Data size in bytes
-    return o
-
-
-def audio_feed(device, fifo, sample_rate, blocksize, latency, channels):
-    send_request(action='sound.stream_recording', device=device, sample_rate=sample_rate,
-                 dtype='int16', fifo=fifo, blocksize=blocksize, latency=latency,
-                 channels=channels)
-
-    try:
-        with open(fifo, 'rb') as f:  # lgtm [py/path-injection]
-            send_header = True
-
-            while True:
-                audio = f.read(blocksize)
-
-                if audio:
-                    if send_header:
-                        audio = gen_header(sample_rate=sample_rate, sample_width=16, channels=channels) + audio
-                        send_header = False
-
-                    yield audio
-    finally:
-        send_request(action='sound.stop_recording')
-
-
-@sound.route('/sound/stream', methods=['GET'])
-@authenticate()
-def get_sound_feed():
-    device = request.args.get('device')
-    sample_rate = request.args.get('sample_rate', 44100)
-    blocksize = request.args.get('blocksize', 512)
-    latency = request.args.get('latency', 0)
-    channels = request.args.get('channels', 1)
-    fifo = request.args.get('fifo', os.path.join(tempfile.gettempdir(), 'inputstream'))
-
-    return Response(audio_feed(device=device, fifo=fifo, sample_rate=sample_rate,
-                               blocksize=blocksize, latency=latency, channels=channels),
-                    mimetype='audio/x-wav;codec=pcm')
-
-
-# vim:sw=4:ts=4:et:

platypush/backend/http/app/streaming/__init__.py

@@ -1,3 +1,3 @@
-from ._base import StreamingRoute, logger
+from ._base import StreamingRoute
 
-__all__ = ['StreamingRoute', 'logger']
+__all__ = ['StreamingRoute']

platypush/backend/http/app/streaming/_base.py

@@ -11,8 +11,6 @@ from platypush.backend.http.app.utils.auth import AuthStatus, get_auth_status
 
 from ..mixins import PubSubMixin
 
-logger = getLogger(__name__)
-
 
 @stream_request_body
 class StreamingRoute(RequestHandler, PubSubMixin, ABC):
@@ -20,6 +18,10 @@ class StreamingRoute(RequestHandler, PubSubMixin, ABC):
     Base class for Tornado streaming routes.
     """
 
+    def __init__(self, *args, **kwargs):
+        super().__init__(*args, **kwargs)
+        self.logger = getLogger(__name__)
+
     @override
     def prepare(self):
         """
@@ -32,7 +34,7 @@ class StreamingRoute(RequestHandler, PubSubMixin, ABC):
                 self.send_error(auth_status.value.code, error=auth_status.value.message)
                 return
 
-        logger.info(
+        self.logger.info(
             'Client %s connected to %s', self.request.remote_ip, self.request.path
         )
 
@@ -63,3 +65,62 @@ class StreamingRoute(RequestHandler, PubSubMixin, ABC):
         authentication and return 401 if authentication fails.
         """
         return True
+
+    @classmethod
+    def _get_redis_queue(cls, *_, **__) -> Optional[str]:
+        """
+        Returns the Redis channel associated with a given set of arguments.
+
+        This is None by default, and it should be implemented by subclasses if
+        required.
+        """
+        return None
+
+    def forward_stream(self, *args, **kwargs):
+        """
+        Utility method that does the following:
+
+            1. It listens for new messages on the subscribed Redis channels;
+            2. It applies a filter on the channel if :meth:`._get_redis_queue`
+               returns a non-null result given ``args`` and ``kwargs``;
+            3. It forward the frames read from the Redis channel(s) to the HTTP client;
+            4. It periodically invokes :meth:`._should_stop` to cleanly
+               terminate when the HTTP client socket is closed.
+
+        """
+        redis_queue = self._get_redis_queue(  # pylint: disable=assignment-from-none
+            *args, **kwargs
+        )
+
+        if redis_queue:
+            self.subscribe(redis_queue)
+
+        try:
+            for msg in self.listen():
+                if self._should_stop():
+                    break
+
+                if redis_queue and msg.channel != redis_queue:
+                    continue
+
+                frame = msg.data
+                if frame:
+                    self.write(frame)
+                    self.flush()
+        finally:
+            if redis_queue:
+                self.unsubscribe(redis_queue)
+
+    def _should_stop(self):
+        """
+        Utility method used by :meth:`._forward_stream` to automatically
+        terminate when the client connection is closed (it can be overridden by
+        the subclasses).
+        """
+        if self._finished:
+            return True
+
+        if self.request.connection and getattr(self.request.connection, 'stream', None):
+            return self.request.connection.stream.closed()  # type: ignore
+
+        return True

platypush/backend/http/app/streaming/plugins/camera.py

@@ -1,19 +1,17 @@
 from enum import Enum
 import json
-from logging import getLogger
 from typing import Optional
 from typing_extensions import override
 
 from tornado.web import stream_request_body
 from platypush.context import get_plugin
 
+from platypush.config import Config
 from platypush.plugins.camera import Camera, CameraPlugin, StreamWriter
 from platypush.utils import get_plugin_name_by_class
 
 from .. import StreamingRoute
 
-logger = getLogger(__name__)
-
 
 class RequestType(Enum):
     """
@@ -31,10 +29,9 @@ class CameraRoute(StreamingRoute):
     Route for camera streams.
     """
 
-    _redis_queue_prefix = '_platypush/camera'
+    _redis_queue_prefix = f'_platypush/{Config.get("device_id") or ""}/camera'
 
     def __init__(self, *args, **kwargs):
-        # TODO Support multiple concurrent requests
         super().__init__(*args, **kwargs)
         self._camera: Optional[Camera] = None
         self._request_type = RequestType.UNKNOWN
@@ -61,29 +58,6 @@ class CameraRoute(StreamingRoute):
 
         return None
 
-    def _should_stop(self):
-        if self._finished:
-            return True
-
-        if self.request.connection and getattr(self.request.connection, 'stream', None):
-            return self.request.connection.stream.closed()  # type: ignore
-
-        return True
-
-    def send_feed(self, camera: CameraPlugin):
-        redis_queue = self._get_redis_queue_by_camera(camera)
-        for msg in self.listen():
-            if self._should_stop():
-                break
-
-            if msg.channel != redis_queue:
-                continue
-
-            frame = msg.data
-            if frame:
-                self.write(frame)
-                self.flush()
-
     def send_frame(self, camera: Camera):
         frame = None
         for _ in range(camera.info.warmup_frames):
@@ -121,8 +95,9 @@ class CameraRoute(StreamingRoute):
 
         return kwargs
 
+    @override
     @classmethod
-    def _get_redis_queue_by_camera(cls, camera: CameraPlugin) -> str:
+    def _get_redis_queue(cls, camera: CameraPlugin, *_, **__) -> str:
         plugin_name = get_plugin_name_by_class(camera.__class__)
         assert plugin_name, f'No such plugin: {plugin_name}'
         return '/'.join(
@@ -144,9 +119,8 @@ class CameraRoute(StreamingRoute):
 
         stream_class = StreamWriter.get_class_by_name(self._extension)
         camera = self._get_camera(plugin)
-        redis_queue = self._get_redis_queue_by_camera(camera)
+        redis_queue = self._get_redis_queue(camera)
         self.set_header('Content-Type', stream_class.mimetype)
-        self.subscribe(redis_queue)
 
         with camera.open(
             stream=True,
@@ -159,6 +133,6 @@ class CameraRoute(StreamingRoute):
             if self._request_type == RequestType.PHOTO:
                 self.send_frame(session)
             elif self._request_type == RequestType.VIDEO:
-                self.send_feed(camera)
+                self.forward_stream(camera)
 
         self.finish()

platypush/backend/http/app/streaming/plugins/sound.py

@@ -0,0 +1,97 @@
+from contextlib import contextmanager
+import json
+from typing import Generator, Optional
+from typing_extensions import override
+
+from tornado.web import stream_request_body
+
+from platypush.backend.http.app.utils import send_request
+from platypush.config import Config
+
+from .. import StreamingRoute
+
+
+@stream_request_body
+class SoundRoute(StreamingRoute):
+    """
+    Route for audio streams.
+    """
+
+    _redis_queue_prefix = f'_platypush/{Config.get("device_id") or ""}/sound'
+
+    def __init__(self, *args, **kwargs):
+        super().__init__(*args, **kwargs)
+        self._audio_headers_written: bool = False
+        """Send the audio file headers before we send the first audio frame."""
+
+    @override
+    @classmethod
+    def path(cls) -> str:
+        return r"/sound/stream\.?([a-zA-Z0-9_]+)?"
+
+    @contextmanager
+    def _audio_stream(self, **kwargs) -> Generator[None, None, None]:
+        response = send_request(
+            'sound.stream_recording',
+            dtype='int16',
+            **kwargs,
+        )
+
+        assert response and not response.is_error(), (
+            'Streaming error: ' + str(response.errors) if response else '(unknown)'
+        )
+
+        yield
+        send_request('sound.stop_recording')
+
+    @override
+    @classmethod
+    def _get_redis_queue(cls, device: Optional[str] = None, *_, **__) -> str:
+        return '/'.join([cls._redis_queue_prefix, *([device] if device else [])])
+
+    def _get_args(self, **kwargs):
+        kwargs.update({k: v[0].decode() for k, v in self.request.arguments.items()})
+        device = kwargs.get('device')
+        return {
+            'device': device,
+            'sample_rate': int(kwargs.get('sample_rate', 44100)),
+            'blocksize': int(kwargs.get('blocksize', 512)),
+            'latency': float(kwargs.get('latency', 0)),
+            'channels': int(kwargs.get('channels', 1)),
+            'format': kwargs.get('format', 'wav'),
+            'redis_queue': kwargs.get('redis_queue', self._get_redis_queue(device)),
+        }
+
+    @staticmethod
+    def _content_type_by_extension(extension: str) -> str:
+        if extension == 'mp3':
+            return 'audio/mpeg'
+        if extension == 'ogg':
+            return 'audio/ogg'
+        if extension == 'wav':
+            return 'audio/wav;codec=pcm'
+        if extension == 'flac':
+            return 'audio/flac'
+        if extension == 'aac':
+            return 'audio/aac'
+        return 'application/octet-stream'
+
+    def get(self, extension: Optional[str] = None) -> None:
+        ext = extension or 'wav'
+        args = self._get_args(format=ext)
+
+        try:
+            with self._audio_stream(**args):
+                self.set_header('Content-Type', self._content_type_by_extension(ext))
+                self.forward_stream(**args)
+
+            self.finish()
+        except AssertionError as e:
+            self.set_header("Content-Type", "application/json")
+            self.set_status(400, str(e))
+            self.finish(json.dumps({"error": str(e)}))
+        except Exception as e:
+            self.set_header("Content-Type", "application/json")
+            self.logger.exception(e)
+            self.set_status(500, str(e))
+            self.finish(json.dumps({"error": str(e)}))

platypush/backend/http/app/utils/streaming.py

@@ -1,3 +1,4 @@
+import logging
 import os
 import importlib
 import inspect
@@ -5,7 +6,9 @@ from typing import List, Type
 
 import pkgutil
 
-from ..streaming import StreamingRoute, logger
+from ..streaming import StreamingRoute
+
+logger = logging.getLogger(__name__)
 
 
 def get_streaming_routes() -> List[Type[StreamingRoute]]:

platypush/plugins/sound/__init__.py

@@ -6,7 +6,10 @@ import time
 
 from enum import Enum
 from threading import Thread, Event, RLock
-from typing import Optional
+from typing import Optional, Union
+
+import sounddevice as sd
+import soundfile as sf
 
 from platypush.context import get_bus
 from platypush.message.event.sound import (
@@ -15,8 +18,10 @@ from platypush.message.event.sound import (
 )
 
 from platypush.plugins import Plugin, action
+from platypush.utils import get_redis
 
 from .core import Sound, Mix
+from ._converter import ConverterProcess
 
 
 class PlaybackState(Enum):
@@ -49,10 +54,11 @@ class SoundPlugin(Plugin):
         * **sounddevice** (``pip install sounddevice``)
         * **soundfile** (``pip install soundfile``)
         * **numpy** (``pip install numpy``)
+        * **ffmpeg** package installed on the system (for streaming support)
+
     """
 
     _STREAM_NAME_PREFIX = 'platypush-stream-'
-    _default_input_stream_fifo = os.path.join(tempfile.gettempdir(), 'inputstream')
 
     def __init__(
         self,
@@ -60,6 +66,7 @@ class SoundPlugin(Plugin):
         output_device=None,
         input_blocksize=Sound._DEFAULT_BLOCKSIZE,
         output_blocksize=Sound._DEFAULT_BLOCKSIZE,
+        ffmpeg_bin: str = 'ffmpeg',
         **kwargs,
     ):
         """
@@ -82,6 +89,9 @@ class SoundPlugin(Plugin):
             Try to increase this value if you get output underflow errors while
             playing. Default: 1024
         :type output_blocksize: int
+
+        :param ffmpeg_bin: Path of the ``ffmpeg`` binary (default: search for
+            the ``ffmpeg`` in the ``PATH``).
         """
 
         super().__init__(**kwargs)
@@ -102,6 +112,7 @@ class SoundPlugin(Plugin):
         self.stream_name_to_index = {}
         self.stream_index_to_name = {}
         self.completed_callback_events = {}
+        self.ffmpeg_bin = ffmpeg_bin
 
     @staticmethod
     def _get_default_device(category):
@@ -111,9 +122,6 @@ class SoundPlugin(Plugin):
         :param category: Device category to query. Can be either input or output
         :type category: str
         """
-
-        import sounddevice as sd
-
         return sd.query_hostapis()[0].get('default_' + category.lower() + '_device')
 
     @action
@@ -155,8 +163,6 @@ class SoundPlugin(Plugin):
 
         """
 
-        import sounddevice as sd
-
         devs = sd.query_devices()
         if category == 'input':
             devs = [d for d in devs if d.get('max_input_channels') > 0]
@@ -166,8 +172,6 @@ class SoundPlugin(Plugin):
         return devs
 
     def _play_audio_callback(self, q, blocksize, streamtype, stream_index):
-        import sounddevice as sd
-
         is_raw_stream = streamtype == sd.RawOutputStream
 
         def audio_callback(outdata, frames, *, status):
@@ -277,8 +281,6 @@ class SoundPlugin(Plugin):
                 'Please specify either a file to play or a ' + 'list of sound objects'
             )
 
-        import sounddevice as sd
-
         if blocksize is None:
             blocksize = self.output_blocksize
 
@@ -301,8 +303,6 @@ class SoundPlugin(Plugin):
             device = self._get_default_device('output')
 
         if file:
-            import soundfile as sf
-
             f = sf.SoundFile(file)
         if not samplerate:
             samplerate = f.samplerate if f else Sound._DEFAULT_SAMPLERATE
@@ -444,10 +444,12 @@ class SoundPlugin(Plugin):
         fifo: Optional[str] = None,
         duration: Optional[float] = None,
         sample_rate: Optional[int] = None,
-        dtype: Optional[str] = 'float32',
+        dtype: str = 'float32',
         blocksize: Optional[int] = None,
-        latency: float = 0,
+        latency: Union[float, str] = 'high',
         channels: int = 1,
+        redis_queue: Optional[str] = None,
+        format: str = 'wav',
     ):
         """
         Return audio data from an audio source
@@ -464,12 +466,13 @@ class SoundPlugin(Plugin):
             float32
         :param blocksize: Audio block size (default: configured
             `input_blocksize` or 2048)
-        :param latency: Device latency in seconds (default: 0)
+        :param latency: Device latency in seconds (default: the device's default high latency)
         :param channels: Number of channels (default: 1)
+        :param redis_queue: If set, the audio chunks will also be published to
+            this Redis channel, so other consumers can process them downstream.
+        :param format: Audio format. Supported: wav, mp3, ogg, aac. Default: wav.
         """
 
-        import sounddevice as sd
-
         self.recording_paused_changed.clear()
 
         if device is None:
@@ -485,30 +488,42 @@ class SoundPlugin(Plugin):
             blocksize = self.input_blocksize
 
         if not fifo:
-            fifo = self._default_input_stream_fifo
+            fifo = os.devnull
 
-        q = queue.Queue()
+        def audio_callback(audio_converter: ConverterProcess):
-
+            # _ = frames
-        def audio_callback(indata, frames, time_duration, status):  # noqa
+            # __ = time
+            def callback(indata, _, __, status):
                 while self._get_recording_state() == RecordingState.PAUSED:
                     self.recording_paused_changed.wait()
 
                 if status:
                     self.logger.warning('Recording callback status: %s', status)
 
-            q.put(indata.copy())
+                audio_converter.write(indata.tobytes())
+
+            return callback
 
         def streaming_thread():
             try:
-                with sd.InputStream(
+                with ConverterProcess(
+                    ffmpeg_bin=self.ffmpeg_bin,
+                    sample_rate=sample_rate,
+                    channels=channels,
+                    dtype=dtype,
+                    chunk_size=self.input_blocksize,
+                    output_format=format,
+                ) as converter, sd.InputStream(
                     samplerate=sample_rate,
                     device=device,
                     channels=channels,
-                    callback=audio_callback,
+                    callback=audio_callback(converter),
                     dtype=dtype,
                     latency=latency,
                     blocksize=blocksize,
-                ), open(fifo, 'wb') as audio_queue:
+                ), open(
+                    fifo, 'wb'
+                ) as audio_queue:
                     self.start_recording()
                     get_bus().post(SoundRecordingStartedEvent())
                     self.logger.info('Started recording from device [%s]', device)
@@ -521,23 +536,23 @@ class SoundPlugin(Plugin):
                         while self._get_recording_state() == RecordingState.PAUSED:
                             self.recording_paused_changed.wait()
 
-                        get_args = (
+                        timeout = (
-                            {
+                            max(
-                                'block': True,
-                                'timeout': max(
                                 0,
                                 duration - (time.time() - recording_started_time),
-                                ),
+                            )
-                            }
                             if duration is not None
-                            else {}
+                            else 1
                         )
 
-                        data = q.get(**get_args)
+                        data = converter.read(timeout=timeout)
-                        if not len(data):
+                        if not data:
                             continue
 
                         audio_queue.write(data)
+                        if redis_queue:
+                            get_redis().publish(redis_queue, data)
+
             except queue.Empty:
                 self.logger.warning('Recording timeout: audio callback failed?')
             finally:
@@ -549,11 +564,8 @@ class SoundPlugin(Plugin):
                 self.logger.info('Removing previous input stream FIFO %s', fifo)
                 os.unlink(fifo)
         else:
-                raise RuntimeError(
-                    f'{fifo} exists and is not a FIFO. Please remove it or rename it'
-                )
-
             os.mkfifo(fifo, 0o644)
+
         Thread(target=streaming_thread).start()
 
     @action
@@ -565,7 +577,7 @@ class SoundPlugin(Plugin):
         sample_rate=None,
         format=None,
         blocksize=None,
-        latency=0,
+        latency='high',
         channels=1,
         subtype='PCM_24',
     ):
@@ -590,7 +602,7 @@ class SoundPlugin(Plugin):
         :param blocksize: Audio block size (default: configured `input_blocksize` or 2048)
         :type blocksize: int
 
-        :param latency: Device latency in seconds (default: 0)
+        :param latency: Device latency in seconds (default: the device's default high latency)
         :type latency: float
 
         :param channels: Number of channels (default: 1)
@@ -613,8 +625,6 @@ class SoundPlugin(Plugin):
             channels,
             subtype,
         ):
-            import sounddevice as sd
-
             self.recording_paused_changed.clear()
 
             if outfile:
@@ -661,8 +671,6 @@ class SoundPlugin(Plugin):
                 )
 
             try:
-                import soundfile as sf
-
                 with sf.SoundFile(
                     outfile,
                     mode='w',
@@ -785,8 +793,6 @@ class SoundPlugin(Plugin):
         :type dtype: str
         """
 
-        import sounddevice as sd
-
         self.recording_paused_changed.clear()
 
         if input_device is None:
@@ -806,8 +812,9 @@ class SoundPlugin(Plugin):
         if blocksize is None:
             blocksize = self.output_blocksize
 
-        # noinspection PyUnusedLocal
+        # _ = frames
-        def audio_callback(indata, outdata, frames, time, status):
+        # __ = time
+        def audio_callback(indata, outdata, _, __, status):
             while self._get_recording_state() == RecordingState.PAUSED:
                 self.recording_paused_changed.wait()
 

platypush/plugins/sound/_converter.py

@@ -0,0 +1,162 @@
+import asyncio
+from asyncio.subprocess import PIPE
+from queue import Empty
+
+from queue import Queue
+from threading import Thread
+from typing import Optional, Self
+
+from platypush.context import get_or_create_event_loop
+
+_dtype_to_ffmpeg_format = {
+    'int8': 's8',
+    'uint8': 'u8',
+    'int16': 's16le',
+    'uint16': 'u16le',
+    'int32': 's32le',
+    'uint32': 'u32le',
+    'float32': 'f32le',
+    'float64': 'f64le',
+}
+"""
+Supported input types:
+    'int8', 'uint8', 'int16', 'uint16', 'int32', 'uint32', 'float32', 'float64'
+"""
+
+_output_format_to_ffmpeg_args = {
+    'wav': ('-f', 'wav'),
+    'ogg': ('-f', 'ogg'),
+    'mp3': ('-f', 'mp3'),
+    'aac': ('-f', 'adts'),
+    'flac': ('-f', 'flac'),
+}
+
+
+class ConverterProcess(Thread):
+    """
+    Wrapper for an ffmpeg converter instance.
+    """
+
+    def __init__(
+        self,
+        ffmpeg_bin: str,
+        sample_rate: int,
+        channels: int,
+        dtype: str,
+        chunk_size: int,
+        output_format: str,
+        *args,
+        **kwargs,
+    ):
+        """
+        :param ffmpeg_bin: Path to the ffmpeg binary.
+        :param sample_rate: The sample rate of the input audio.
+        :param channels: The number of channels of the input audio.
+        :param dtype: The (numpy) data type of the raw input audio.
+        :param chunk_size: Number of bytes that will be read at once from the
+            ffmpeg process.
+        :param output_format: Output audio format.
+        """
+        super().__init__(*args, **kwargs)
+
+        ffmpeg_format = _dtype_to_ffmpeg_format.get(dtype)
+        assert ffmpeg_format, (
+            f'Unsupported data type: {dtype}. Supported data types: '
+            f'{list(_dtype_to_ffmpeg_format.keys())}'
+        )
+
+        self._ffmpeg_bin = ffmpeg_bin
+        self._ffmpeg_format = ffmpeg_format
+        self._sample_rate = sample_rate
+        self._channels = channels
+        self._chunk_size = chunk_size
+        self._output_format = output_format
+        self._closed = False
+        self._out_queue = Queue()
+        self.ffmpeg = None
+        self._loop = None
+
+    def __enter__(self) -> Self:
+        self.start()
+        return self
+
+    def __exit__(self, *_, **__):
+        if self.ffmpeg and self._loop:
+            self._loop.call_soon_threadsafe(self.ffmpeg.kill)
+
+        self.ffmpeg = None
+
+        if self._loop:
+            self._loop = None
+
+    def _check_ffmpeg(self):
+        assert (
+            self.ffmpeg and self.ffmpeg.returncode is None
+        ), 'The ffmpeg process has already terminated'
+
+    def _get_format_args(self):
+        ffmpeg_args = _output_format_to_ffmpeg_args.get(self._output_format)
+        assert ffmpeg_args, (
+            f'Unsupported output format: {self._output_format}. Supported formats: '
+            f'{list(_output_format_to_ffmpeg_args.keys())}'
+        )
+
+        return ffmpeg_args
+
+    async def _audio_proxy(self, timeout: Optional[float] = None):
+        self.ffmpeg = await asyncio.create_subprocess_exec(
+            self._ffmpeg_bin,
+            '-f',
+            self._ffmpeg_format,
+            '-ar',
+            str(self._sample_rate),
+            '-ac',
+            str(self._channels),
+            '-i',
+            'pipe:',
+            *self._get_format_args(),
+            'pipe:',
+            stdin=PIPE,
+            stdout=PIPE,
+        )
+
+        try:
+            await asyncio.wait_for(self.ffmpeg.wait(), 0.1)
+        except asyncio.TimeoutError:
+            pass
+
+        while self._loop and self.ffmpeg and self.ffmpeg.returncode is None:
+            self._check_ffmpeg()
+            assert (
+                self.ffmpeg and self.ffmpeg.stdout
+            ), 'The stdout is closed for the ffmpeg process'
+
+            try:
+                data = await asyncio.wait_for(
+                    self.ffmpeg.stdout.read(self._chunk_size), timeout
+                )
+                self._out_queue.put(data)
+            except asyncio.TimeoutError:
+                self._out_queue.put(b'')
+
+    def write(self, data: bytes):
+        self._check_ffmpeg()
+        assert (
+            self.ffmpeg and self._loop and self.ffmpeg.stdin
+        ), 'The stdin is closed for the ffmpeg process'
+
+        self._loop.call_soon_threadsafe(self.ffmpeg.stdin.write, data)
+
+    def read(self, timeout: Optional[float] = None) -> Optional[bytes]:
+        try:
+            return self._out_queue.get(timeout=timeout)
+        except Empty:
+            return None
+
+    def run(self):
+        super().run()
+        self._loop = get_or_create_event_loop()
+        self._loop.run_until_complete(self._audio_proxy(timeout=1))
+
+
+# vim:sw=4:ts=4:et:

platypush/plugins/sound/manifest.yaml

@@ -11,5 +11,9 @@ manifest:
     - sounddevice
     - soundfile
     - numpy
+    apt:
+    - ffmpeg
+    pacman:
+    - ffmpeg
   package: platypush.plugins.sound
   type: plugin