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Source reader classes

The VideoStreamer class streams video from a source (file or camera) and retrieves frames in real-time, ensuring that the current frame is always processed without delay. Unlike cv2.VideoCapture, which might introduce a delay while waiting for the next frame in the stream, VideoStreamer fetches the frame at the current time, making it ideal for real-time processing.

kano.lab.source_reader.VideoStreamer

A class to stream video from a source (file or camera), continuously read frames, and store them in a queue.

Parameters:

Name Type Description Default
source str

Path to the video source or camera index.

 required
reconnect bool

Whether to reconnect to the video source if the connection is lost. Default is True.

 True
Source code in kano\lab\source_reader.py 
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class VideoStreamer:
    """
    A class to stream video from a source (file or camera), continuously read frames, and store them in a queue.

    Args:
        source (str): Path to the video source or camera index.
        reconnect (bool): Whether to reconnect to the video source if the connection is lost. Default is True.
    """

    def __init__(
        self, source: str, reconnect: bool = True, reconnect_time: float = 2
    ):
        """
        Initializes the VideoStreamer class to stream video from the specified source.

        Args:
            source (str): The path to the video source or camera index.
            reconnect (bool): Whether to reconnect to the video source if the connection is lost.
            reconnect_time (float): Time to play the source after out of frames or connection lost
        """
        self.source = source
        self.frame_queue = Queue(maxsize=5)
        thread = threading.Thread(target=self._read_frames)
        thread.start()
        thread.daemon = True
        self.stop = False
        self.reconnect = reconnect
        self.reconnect_time = reconnect_time

    def _read_frames(self):
        """
        Continuously reads frames from the video source and stores them in a queue.

        If the video source is lost, it attempts to reconnect if `self.reconnect` is True.
        """
        cap = cv2.VideoCapture(self.source)

        if not cap.isOpened():
            raise ValueError(f"Error when playing {self.source}.")

        source_fps = cap.get(cv2.CAP_PROP_FPS)
        running = True
        fps_counter = FPSCounter()

        while running:
            ret, frame = cap.read()

            if not ret or not self.stop:
                if self.reconnect:
                    print("Reconnect...")
                    time.sleep(self.reconnect_time)
                    cap = cv2.VideoCapture(self.source)
                    fps_counter = FPSCounter()
                    continue
                break

            fps_counter.update()
            fps_counter.keep_target_fps(source_fps)

            try:
                self.frame_queue.put_nowait(frame)
            except:
                pass

        cap.release()

    def get_latest_frame(self):
        """
        Retrieves the latest frame from the queue.

        Returns:
            frame (ndarray): The most recent frame from the video source.
        """
        return self.frame_queue.get()

    def stop_stream(self):
        """
        Stop the stream thread
        """
        self.stop = True

__init__(source, reconnect=True, reconnect_time=2)

Initializes the VideoStreamer class to stream video from the specified source.

Parameters:

Name Type Description Default
source str

The path to the video source or camera index.

 required
reconnect bool

Whether to reconnect to the video source if the connection is lost.

 True
reconnect_time float

Time to play the source after out of frames or connection lost

 2
Source code in kano\lab\source_reader.py 
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def __init__(
    self, source: str, reconnect: bool = True, reconnect_time: float = 2
):
    """
    Initializes the VideoStreamer class to stream video from the specified source.

    Args:
        source (str): The path to the video source or camera index.
        reconnect (bool): Whether to reconnect to the video source if the connection is lost.
        reconnect_time (float): Time to play the source after out of frames or connection lost
    """
    self.source = source
    self.frame_queue = Queue(maxsize=5)
    thread = threading.Thread(target=self._read_frames)
    thread.start()
    thread.daemon = True
    self.stop = False
    self.reconnect = reconnect
    self.reconnect_time = reconnect_time

get_latest_frame()

Retrieves the latest frame from the queue.

Returns:

Name Type Description
frame ndarray

The most recent frame from the video source.
Source code in kano\lab\source_reader.py 
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def get_latest_frame(self):
    """
    Retrieves the latest frame from the queue.

    Returns:
        frame (ndarray): The most recent frame from the video source.
    """
    return self.frame_queue.get()

stop_stream()

Stop the stream thread

Source code in kano\lab\source_reader.py 
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def stop_stream(self):
    """
    Stop the stream thread
    """
    self.stop = True