Add backend/app/utils/hls.py
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backend/app/utils/hls.py
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206
backend/app/utils/hls.py
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"""HLS preview manager for live video preview via HTTP Live Streaming."""
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import asyncio
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import logging
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from pathlib import Path
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from ..config import Settings
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logger = logging.getLogger(__name__)
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class HLSPreviewManager:
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"""
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Manages FFmpeg HLS transcoding processes for video preview.
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Creates per-port HLS streams at low bitrate for web browser playback.
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"""
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def __init__(self, settings: Settings, hls_dir: str = "/tmp/hls"):
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"""Initialize HLS preview manager.
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Args:
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settings: Application settings with ffmpeg_path
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hls_dir: Directory for HLS playlist and segment files
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"""
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self.settings = settings
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self.hls_dir = Path(hls_dir)
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self._processes: dict[int, asyncio.subprocess.Process] = {}
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async def start_preview(self, port_index: int) -> None:
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"""
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Start HLS transcoding for a port.
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Creates {hls_dir}/port_{port_index}.m3u8 and segment files.
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No-op if already running for this port.
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Args:
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port_index: 0-based port index
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"""
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if port_index in self._processes and self._processes[port_index] is not None:
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logger.info(f"Port {port_index}: HLS preview already running")
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return
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# Ensure hls_dir exists
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self.hls_dir.mkdir(parents=True, exist_ok=True)
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# Build FFmpeg command
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command = self._build_hls_command(port_index)
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logger.info(f"Port {port_index}: Starting HLS preview: {' '.join(command)}")
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# Spawn subprocess
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try:
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process = await asyncio.create_subprocess_exec(
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*command,
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stdin=asyncio.subprocess.PIPE,
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stderr=asyncio.subprocess.PIPE,
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stdout=asyncio.subprocess.PIPE,
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)
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self._processes[port_index] = process
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logger.info(f"Port {port_index}: HLS preview started (PID: {process.pid})")
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except Exception as e:
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logger.error(f"Port {port_index}: Failed to start HLS preview: {e}")
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raise
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async def stop_preview(self, port_index: int) -> None:
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"""
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Stop HLS transcoding for a port.
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Graceful shutdown: stdin q -> SIGTERM -> SIGKILL.
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No-op if not running.
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Args:
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port_index: 0-based port index
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"""
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if port_index not in self._processes or self._processes[port_index] is None:
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logger.info(f"Port {port_index}: HLS preview not running")
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return
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process = self._processes[port_index]
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logger.info(f"Port {port_index}: Stopping HLS preview (PID: {process.pid})")
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try:
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# Step 1: Try graceful quit via stdin
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if process.stdin and not process.stdin.is_closing():
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try:
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process.stdin.write(b"q\n")
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await process.stdin.drain()
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logger.debug(f"Port {port_index}: Sent quit command to stdin")
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except (BrokenPipeError, ConnectionResetError):
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logger.debug(f"Port {port_index}: Could not write to stdin (already closed)")
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# Step 2: Wait up to 3 seconds for graceful shutdown
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try:
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await asyncio.wait_for(process.wait(), timeout=3.0)
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logger.info(f"Port {port_index}: HLS process exited gracefully")
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self._processes[port_index] = None
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return
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except asyncio.TimeoutError:
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logger.warning(f"Port {port_index}: Graceful quit timeout, sending SIGTERM")
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# Step 3: Send SIGTERM
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try:
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process.terminate()
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except ProcessLookupError:
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logger.debug(f"Port {port_index}: Process already terminated")
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self._processes[port_index] = None
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return
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# Step 4: Wait up to 2 seconds for SIGTERM to work
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try:
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await asyncio.wait_for(process.wait(), timeout=2.0)
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logger.info(f"Port {port_index}: HLS process exited after SIGTERM")
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self._processes[port_index] = None
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return
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except asyncio.TimeoutError:
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logger.warning(f"Port {port_index}: SIGTERM timeout, sending SIGKILL")
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# Step 5: Send SIGKILL
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try:
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process.kill()
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await process.wait()
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logger.info(f"Port {port_index}: HLS process killed")
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except ProcessLookupError:
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logger.debug(f"Port {port_index}: Process already killed")
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except Exception as e:
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logger.error(f"Port {port_index}: Error stopping HLS preview: {e}")
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finally:
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self._processes[port_index] = None
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async def stop_all(self) -> None:
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"""Stop all HLS preview processes."""
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logger.info("Stopping all HLS preview processes")
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port_indices = list(self._processes.keys())
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for port_index in port_indices:
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await self.stop_preview(port_index)
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logger.info("All HLS preview processes stopped")
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def get_playlist_path(self, port_index: int) -> Path:
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"""Return path to HLS playlist file for given port.
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Args:
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port_index: 0-based port index
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Returns:
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Path to the .m3u8 playlist file
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"""
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return self.hls_dir / f"port_{port_index}.m3u8"
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def is_previewing(self, port_index: int) -> bool:
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"""Return True if HLS preview is running for this port.
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Args:
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port_index: 0-based port index
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Returns:
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True if preview is active and process is running
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"""
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if port_index not in self._processes:
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return False
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process = self._processes[port_index]
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return process is not None and not process.done()
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def _build_hls_command(self, port_index: int) -> list[str]:
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"""
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Build FFmpeg HLS transcoding command.
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Args:
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port_index: 0-based port index
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Returns:
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List of command arguments for FFmpeg
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Command structure:
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ffmpeg -f deltacast -i deltacast://{port_index}
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-c:v libx264 -preset ultrafast -tune zerolatency
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-b:v 5M -s 1280x720
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-c:a aac -b:a 128k
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-f hls
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-hls_time 5
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-hls_list_size 3
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-hls_flags delete_segments
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{hls_dir}/port_{port_index}.m3u8
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"""
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playlist_path = self.get_playlist_path(port_index)
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command = [
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self.settings.ffmpeg_path,
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# Input: Deltacast SDI
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"-f", "deltacast",
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"-i", f"deltacast://{port_index}",
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# Video codec: x264 with low latency settings
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"-c:v", "libx264",
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"-preset", "ultrafast",
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"-tune", "zerolatency",
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"-b:v", "5M",
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"-s", "1280x720",
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# Audio codec: AAC
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"-c:a", "aac",
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"-b:a", "128k",
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# HLS output format
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"-f", "hls",
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"-hls_time", "5",
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"-hls_list_size", "3",
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"-hls_flags", "delete_segments",
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# Output path
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str(playlist_path),
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]
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return command
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