KNEO-Academy/src/models/video_thread.py

"""
video_thread.py - Video Capture Thread

This module provides a QThread-based video capture worker for webcam streaming.
It handles camera connection, frame capture, and automatic reconnection.
"""

import cv2
import time
import threading
from PyQt5.QtCore import QThread, pyqtSignal
from PyQt5.QtGui import QImage


class VideoThread(QThread):
    """
    Thread for capturing video frames from a webcam.

    Emits frames as QImage objects via Qt signals for display in the UI.
    Handles camera connection with timeout and automatic reconnection.

    Signals:
        change_pixmap_signal: Emitted with each new frame (QImage)
        camera_error_signal: Emitted when camera errors occur (str)
    """

    change_pixmap_signal = pyqtSignal(QImage)
    camera_error_signal = pyqtSignal(str)  # Camera error signal

    def __init__(self):
        """Initialize the VideoThread with default settings."""
        super().__init__()
        self._run_flag = True
        self._camera_open_attempts = 0
        self._max_attempts = 3
        self._camera_timeout = 5  # Camera open timeout in seconds

    def _open_camera_with_timeout(self, camera_index, backend=None):
        """
        Open camera with timeout mechanism.

        Args:
            camera_index (int): Index of the camera to open.
            backend: OpenCV video capture backend (e.g., cv2.CAP_DSHOW).

        Returns:
            cv2.VideoCapture: Opened camera object, or None if failed.
        """
        cap = None
        open_success = False

        def try_open():
            nonlocal cap, open_success
            try:
                if backend is not None:
                    cap = cv2.VideoCapture(camera_index, backend)
                else:
                    cap = cv2.VideoCapture(camera_index)
                open_success = cap is not None and cap.isOpened()
            except Exception as e:
                print(f"Exception while opening camera: {e}")
                open_success = False

        # Try to open camera in a separate thread
        thread = threading.Thread(target=try_open)
        thread.daemon = True
        thread.start()
        thread.join(timeout=self._camera_timeout)

        if thread.is_alive():
            print(f"Camera open timeout ({self._camera_timeout} seconds)")
            return None

        if open_success:
            return cap
        else:
            if cap is not None:
                cap.release()
            return None

    def run(self):
        """
        Main thread execution loop.

        Attempts to open the camera with multiple backends and retries.
        Captures frames and emits them as QImage signals.
        """
        # Try multiple times to open camera
        while self._camera_open_attempts < self._max_attempts and self._run_flag:
            self._camera_open_attempts += 1
            print(f"Attempting to open camera (attempt {self._camera_open_attempts}/{self._max_attempts})...")

            # Try DirectShow backend first (usually faster on Windows)
            cap = self._open_camera_with_timeout(0, cv2.CAP_DSHOW)
            if cap is None:
                print("Unable to open camera with DirectShow, trying default backend")
                cap = self._open_camera_with_timeout(0)
                if cap is None:
                    print("Unable to open camera with any backend, retrying in 1 second...")
                    time.sleep(1)
                    continue

            # Set camera properties for better performance
            # Lower resolution for faster startup and higher frame rate
            cap.set(cv2.CAP_PROP_FRAME_WIDTH, 640)
            cap.set(cv2.CAP_PROP_FRAME_HEIGHT, 480)
            cap.set(cv2.CAP_PROP_FPS, 30)

            # Set buffer size to 1 to reduce latency
            cap.set(cv2.CAP_PROP_BUFFERSIZE, 1)

            # Warm up camera by discarding first few frames
            for _ in range(5):
                cap.read()

            # Camera opened successfully, reset attempt count
            self._camera_open_attempts = 0

            # Main capture loop
            while self._run_flag:
                ret, frame = cap.read()
                if ret:
                    # Convert to RGB format
                    frame = cv2.cvtColor(frame, cv2.COLOR_BGR2RGB)
                    height, width, channel = frame.shape
                    bytes_per_line = channel * width
                    qt_image = QImage(frame.data, width, height, bytes_per_line, QImage.Format_RGB888)
                    self.change_pixmap_signal.emit(qt_image)
                else:
                    print("Unable to read camera frame, camera may be disconnected")
                    break

            # Release camera resources
            cap.release()

            # If stopped by stop signal, don't retry
            if not self._run_flag:
                break

            print("Camera connection lost, attempting to reconnect...")

        if self._camera_open_attempts >= self._max_attempts:
            print("Maximum attempts reached, unable to open camera")

    def stop(self):
        """Stop the video capture thread."""
        try:
            print("Stopping camera thread...")
            self._run_flag = False
            # Wait for thread to finish
            if self.isRunning():
                self.wait()
            print("Camera thread stopped")
        except Exception as e:
            print(f"Error stopping camera thread: {e}")
            import traceback
            print(traceback.format_exc())