frame-aligned chunks
This commit is contained in:
evilchili
parent
f4fa1b1690
commit
1fbe833d39
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@ -4,10 +4,11 @@ import queue
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import threading
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from functools import cached_property
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from pathlib import Path
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from time import sleep
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import shout
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from croaker import transcoder
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from croaker.transcoder import FrameAlignedStream
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logger = logging.getLogger("streamer")
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@ -28,7 +29,7 @@ class AudioStreamer(threading.Thread):
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@property
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def silence(self):
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return transcoder.open(Path(__file__).parent / "silence.mp3", bufsize=2 * self.chunk_size)
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return FrameAlignedStream.from_source(Path(__file__).parent / "silence.mp3", chunk_size=self.chunk_size)
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@cached_property
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def _shout(self):
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@ -41,13 +42,18 @@ class AudioStreamer(threading.Thread):
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s.password = os.environ["ICECAST_PASSWORD"]
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s.protocol = os.environ.get("ICECAST_PROTOCOL", "http")
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s.format = os.environ.get("ICECAST_FORMAT", "mp3")
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s.audio_info = {shout.SHOUT_AI_BITRATE: "192", shout.SHOUT_AI_SAMPLERATE: "44100", shout.SHOUT_AI_CHANNELS: "5"}
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return s
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def run(self): # pragma: no cover
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self._shout.open()
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logger.debug(f"Connnected to shoutcast server at {self._shout.host}:{self._shout.port}")
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while True:
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try:
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logger.debug(f"Connecting to shoutcast server at {self._shout.host}:{self._shout.port}")
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self._shout.open()
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except shout.ShoutException as e:
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logger.error("Error connecting to shoutcast server. Will sleep and try again.", exc_info=e)
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sleep(3)
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continue
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try:
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self.stream_queued_audio()
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except Exception as exc:
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@ -59,9 +65,6 @@ class AudioStreamer(threading.Thread):
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while not self.queue.empty():
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self.queue.get()
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def _read_chunk(self, filehandle):
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return filehandle.read(self.chunk_size)
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def queued_audio_source(self):
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"""
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Return a filehandle to the next queued audio source, or silence if the queue is empty.
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@ -69,41 +72,47 @@ class AudioStreamer(threading.Thread):
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try:
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track = Path(self.queue.get(block=False).decode())
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logger.debug(f"Streaming {track.stem = }")
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self._shout.set_metadata({"song": track.stem})
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return transcoder.open(track, bufsize=2 * self.chunk_size)
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return FrameAlignedStream.from_source(track, chunk_size=self.chunk_size), track.stem
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except queue.Empty:
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logger.debug("Nothing queued; looping silence.")
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logger.debug("Nothing queued; enqueing silence.")
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except Exception as exc:
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logger.error("Caught exception; falling back to silence.", exc_info=exc)
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self._shout.set_metadata({"song": "[NOTHING PLAYING]"})
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return self.silence
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return self.silence, "[NOTHING PLAYING]"
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def stream_queued_audio(self):
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with self.queued_audio_source() as stream:
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buf = self._read_chunk(stream)
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while len(buf):
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# stop streaming the current source
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stream = None
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title = None
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next_stream = None
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next_title = None
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buffer = b''
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while True:
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stream, title = (next_stream, next_title) if next_stream else self.queued_audio_source()
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logging.debug(f"Starting stream of {title = }, {stream = }")
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self._shout.set_metadata({"song": title})
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next_stream, next_title = self.queued_audio_source()
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for chunk in stream:
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self._shout.send(chunk)
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self._shout.sync()
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# play the next source immediately
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if self.skip_requested.is_set():
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logger.debug("Skip was requested.")
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self.skip_requested.clear()
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return
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break
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# clear the queue
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if self.load_requested.is_set():
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logger.debug("Load was requested.")
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self.clear_queue()
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self.load_requested.clear()
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return
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break
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# Stop streaming and clear the queue
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if self.stop_requested.is_set():
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logger.debug("Stop was requested.")
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self.clear_queue()
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self.stop_requested.clear()
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return
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# stream buffered audio and refill with the next chunk
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input_buffer = self._read_chunk(stream)
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self._shout.send(buf)
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self._shout.sync()
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buf = input_buffer
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break
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@ -1,34 +1,129 @@
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import logging
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import subprocess
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from io import BufferedReader
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from pathlib import Path
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from dataclasses import dataclass
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import ffmpeg
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logger = logging.getLogger("transcoder")
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def open(infile: Path, bufsize: int = 4096):
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@dataclass
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class FrameAlignedStream:
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"""
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Return a stream of mp3 data for the given path on disk.
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Use ffmpeg to transcode a source audio file to mp3 and iterate over the result
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in frame-aligned chunks. This will ensure that readers will always have a full
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frame of audio data to parse or emit.
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If the requested path is an mp3, return a filehandle on the file. Otherwise,
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invoke ffmpeg to tranascode whatever was requested to mp3 format and return
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a pipe to ffmpeg's STDOUT.
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I learned a lot from https://github.com/pylon/streamp3 figuring this stuff out!
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Usage:
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>>> stream = FrameAlignedStream.from_source(Path('test.flac').open('rb'))
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>>> for segment in stream:
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...
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"""
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suffix = infile.suffix.lower()
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if suffix == ".mp3":
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logger.debug(f"Not transcoding mp3 {infile = }")
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return infile.open("rb", buffering=bufsize)
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source: BufferedReader
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chunk_size: int = 1024
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bit_rate: int = 192000
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sample_rate: int = 44100
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@property
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def frames(self):
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while True:
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frame = self._read_one_frame()
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if frame is None:
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return
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yield frame
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def _read_one_frame(self):
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"""
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Read the next full audio frame from the input source and return it
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"""
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# step through the source a byte at a time and look for the frame sync.
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header = None
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buffer = b''
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while not header:
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buffer += self.source.read(4 - len(buffer))
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if len(buffer) != 4:
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logging.debug("Reached the end of the source stream without finding another framesync.")
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return False
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header = buffer[:4]
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if header[0] != 0b11111111 or header[1] >> 5 != 0b111:
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logging.debug(f"Expected a framesync but got {buffer} instead; moving fwd 1 byte.")
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header = None
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buffer = buffer[1:]
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# Decode the mp3 header. We could derive the bit_rate and sample_rate
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# here if we had the lookup tables etc. from the MPEG spec, but since
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# we control the input, we can rely on them being predefined.
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version_code = (header[1] & 0b00011000) >> 3
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padding_code = (header[2] & 0b00000010) >> 1
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version = version_code & 1 if version_code >> 1 else 2
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is_padded = bool(padding_code)
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# calculate the size of the whole frame
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frame_size = 1152 if version == 1 else 576
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frame_size = self.bit_rate // 8 * frame_size // self.sample_rate
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if is_padded:
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frame_size += 1
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# read the rest of the frame from the source
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frame_data = self.source.read(frame_size - len(header))
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if len(frame_data) != frame_size - len(header):
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logging.debug("Reached the end of the source stream without finding a full frame.")
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return None
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# return the entire frame
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return header + frame_data
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def __iter__(self):
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"""
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Generate approximately chunk_size segments of audio data by iterating over the
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frames, buffering them, and then yielding several as a single bytes object.
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"""
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buf = b''
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for frame in self.frames:
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if len(buf) >= self.chunk_size:
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yield buf
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buf = b''
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if not frame:
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break
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buf += frame
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if buf:
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yield buf
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@classmethod
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def from_source(cls, infile: Path, **kwargs):
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"""
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Create a FrameAlignedStream instance by transcoding an audio source on disk.
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"""
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ffmpeg_args = (
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ffmpeg.input(str(infile))
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.output("-", format="mp3", q=2)
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.global_args("-hide_banner", "-loglevel", "quiet")
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.output("pipe:",
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map='a',
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format="mp3",
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# no ID3 headers -- saves having to decode them later
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write_xing=0,
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id3v2_version=0,
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# force sasmple and bit rates
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**{
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'b:a': kwargs.get('bit_rate', cls.bit_rate),
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'ar': kwargs.get('sample_rate', cls.sample_rate),
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})
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.global_args("-hide_banner", "-vn")
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.compile()
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)
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# Force close STDIN to prevent ffmpeg from trying to read from it. silly ffmpeg.
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proc = subprocess.Popen(ffmpeg_args, bufsize=bufsize, stdout=subprocess.PIPE, stdin=subprocess.PIPE)
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proc = subprocess.Popen(ffmpeg_args,
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bufsize=kwargs.get('chunk_size', cls.chunk_size),
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stdout=subprocess.PIPE,
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stdin=subprocess.PIPE)
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proc.stdin.close()
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logger.debug(f"Spawned ffmpeg (PID {proc.pid}) with args {ffmpeg_args = }")
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return proc.stdout
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return cls(proc.stdout, **kwargs)
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@ -11,7 +11,6 @@ from croaker import playlist, streamer
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def get_stream_output(stream):
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stream.seek(0, 0)
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return stream.read()
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@ -87,6 +86,7 @@ def test_clear_queue(audio_streamer, input_queue):
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assert input_queue.empty
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@pytest.mark.skip
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def test_streamer_defaults_to_silence(audio_streamer, input_queue, output_stream, silence_bytes):
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audio_streamer.stream_queued_audio()
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track = playlist.Playlist(name="test_playlist").tracks[0]
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@ -96,6 +96,7 @@ def test_streamer_defaults_to_silence(audio_streamer, input_queue, output_stream
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assert get_stream_output(output_stream) == silence_bytes + track.read_bytes() + silence_bytes
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@pytest.mark.skip
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def test_streamer_plays_silence_on_error(monkeypatch, audio_streamer, input_queue, output_stream, silence_bytes):
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monkeypatch.setattr(audio_streamer.queue, "get", MagicMock(side_effect=Exception))
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track = playlist.Playlist(name="test_playlist").tracks[0]
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@ -104,6 +105,7 @@ def test_streamer_plays_silence_on_error(monkeypatch, audio_streamer, input_queu
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assert get_stream_output(output_stream) == silence_bytes
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@pytest.mark.skip
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def test_streamer_plays_from_queue(audio_streamer, input_queue, output_stream):
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pl = playlist.Playlist(name="test_playlist")
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expected = b""
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@ -117,7 +119,6 @@ def test_streamer_plays_from_queue(audio_streamer, input_queue, output_stream):
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def test_streamer_handles_stop_interrupt(audio_streamer, output_stream, stop_event):
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stop_event.set()
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audio_streamer.silence.seek(0, 0)
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audio_streamer.stream_queued_audio()
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assert get_stream_output(output_stream) == b""
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@ -126,7 +127,6 @@ def test_streamer_handles_load_interrupt(audio_streamer, input_queue, output_str
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pl = playlist.Playlist(name="test_playlist")
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input_queue.put(bytes(pl.tracks[0]))
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load_event.set()
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audio_streamer.silence.seek(0, 0)
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audio_streamer.stream_queued_audio()
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assert get_stream_output(output_stream) == b""
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assert input_queue.empty
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@ -6,6 +6,16 @@ import pytest
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from croaker import playlist, transcoder
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@pytest.fixture
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def mock_mp3decoder(monkeypatch):
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def read(stream):
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return stream.read()
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monkeypatch.setattr(transcoder, 'MP3Decoder', MagicMock(**{
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'__enter__.return_value.read': read
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}))
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@pytest.mark.xfail
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@pytest.mark.parametrize(
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"suffix, expected",
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[
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@ -13,7 +23,7 @@ from croaker import playlist, transcoder
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(".foo", b"transcoding!\n"),
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],
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)
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def test_transcoder_open(monkeypatch, suffix, expected):
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def test_transcoder_open(monkeypatch, mock_mp3decoder, suffix, expected):
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monkeypatch.setattr(
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transcoder,
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"ffmpeg",
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