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• Monitoring for failure and quickly restarting systemd service

  16 février 2024, par mzrt

  I am running a 24/7 youtube stream on Ubuntu. My ffmpeg command is wrapped in a systemd service. On several occasions the ffmpeg command has failed and systemd has not restarted quickly enough to keep the youtube stream alive. When this happens I need to daemon-reload and restart the systemd service.

  


  To counter this I have written a bash script that checks the log for stream ending errors, however, it does not seem to be working. I have had failures since implementing this script, and it did not seem to have been triggered.

  


  two questions :

  


  

  1. is there a more efficient way to do what I am doing ?

  


  2. if not, can anyone identify what I am doing wrong ?

  


  


  #!/bin/bash

RESET=0

while true; do
    # Get the current time minus 1 minute
    LAST_1_MINUTE=$(date -d '1 minute ago' '+%b %e %H:%M:%S')
    
    # Run the command to check for the error within the last minute
    if journalctl --since "$LAST_1_MINUTE" | grep -qi "Error writing trailer"; then
        if [ $RESET -lt 1 ]; then
            # Perform actions if error is detected
            sudo systemctl daemon-reload && \
            echo "Restarting master.service by monitor.sh script at $(date)" >> /var/log/monitor.log && \
            sudo systemctl restart master.service
            RESET=2
        fi
    else
        RESET=$((RESET - 1))
    fi

    # Wait for 20 seconds before the next iteration
    sleep 20
done


  


• Efficiently Fetching the Latest Frame from a Live Stream using OpenCV in Python

  10 juillet 2023, par Nicolantonio De Bari

  Problem :

  


  I have a FastAPI server that connects to a live video feed using cv2.VideoCapture. The server then uses OpenCV to process the frames for object detection and sends the results to a WebSocket. Here's the relevant part of my code :

  


  class VideoProcessor:
    # ...

    def update_frame(self, url):
        logger.info("update_frame STARTED")
        cap = cv2.VideoCapture(url)
        while self.capture_flag:
            ret, frame = cap.read()
            if ret:
                frame = cv2.resize(frame, (1280, 720))
                self.current_frame = frame
            else:
                logger.warning("Failed to read frame, retrying connection...")
                cap.release()
                time.sleep(1)
                cap = cv2.VideoCapture(url)

    async def start_model(self, url, websocket: WebSocket):
        # ...
        threading.Thread(target=self.update_frame, args=(url,), daemon=True).start()
        while self.capture_flag:
            if self.current_frame is not None:
                frame = cv2.resize(self.current_frame, (1280, 720))
                bbx = await self.process_image(frame)
                await websocket.send_text(json.dumps(bbx))
                await asyncio.sleep(0.1)


  


  Currently, I'm using a separate thread (update_frame) to continuously fetch frames from the live feed and keep the most recent one in self.current_frame.

  


  The issue with this method is that it uses multi-threading and continuously reads frames in the background, which is quite CPU-intensive. The cv2.VideoCapture.read() function fetches the oldest frame in the buffer, and OpenCV does not provide a direct way to fetch the latest frame.

  


  Goal

  


  I want to optimize this process by eliminating the need for a separate thread and fetching the latest frame directly when I need it. I want to ensure that each time I process a frame in start_model, I'm processing the most recent frame from the live feed.

  


  I have considered a method of continuously calling cap.read() in a tight loop to "clear" the buffer, but I understand that this is inefficient and can lead to high CPU usage.

  


  Attempt :

  


  What I then tried to do is use ffmpeg & subprocess to get the latest frame, but I dont seem to understand how to get the latest frame then.

  


  async def start_model(self, url, websocket: WebSocket):
    try:
        logger.info("Model Started")
        self.capture_flag = True

        command = ["ffmpeg", "-i", url, "-f", "image2pipe", "-pix_fmt", "bgr24", "-vcodec", "rawvideo", "-"]
        pipe = subprocess.Popen(command, stdout=subprocess.PIPE, bufsize=10**8)

        while self.capture_flag:
            raw_image = pipe.stdout.read(1280*720*3)  # read 720p frame (BGR)
            if raw_image == b'':
                logger.warning("Failed to read frame, retrying connection...")
                await asyncio.sleep(1) # delay for 1 second before retrying
                continue
            
            frame = np.fromstring(raw_image, dtype='uint8')
            frame = frame.reshape((720, 1280, 3))
            if frame is not None:
                self.current_frame = frame
                frame = cv2.resize(self.current_frame, (1280, 720))
                bbx = await self.process_image(frame)
                await websocket.send_text(json.dumps(bbx))
                await asyncio.sleep(0.1)
                
        pipe.terminate()

    except WebSocketDisconnect:
        logger.info("WebSocket disconnected during model operation")
        self.capture_flag = False  # Ensure to stop the model operation when the WebSocket disconnects


  


  Question

  


  Is there a more efficient way to fetch the latest frame from a live stream using OpenCV in Python ? Can I modify my current setup to get the newest frame without having to read all the frames in a separate thread ?
Or is there another library that I could use ?

  


  I know a similar question has been asked, but not related to video streaming.

  


• Cannot stream video from VLC docker

  4 avril 2023, par Snake Eyes

  I have Dockerfile :

  


  FROM fedora:34

ARG VLC_UID="1000"
ARG VLC_GID="1000"

ENV HOME="/data"


RUN groupadd -g "${VLC_GID}" vlc && \
    useradd -m -d /data -s /bin/sh -u "${VLC_UID}" -g "${VLC_GID}" vlc && \
    dnf upgrade -y && \
    rpm -ivh "https://download1.rpmfusion.org/free/fedora/rpmfusion-free-release-34.noarch.rpm" && \
    dnf upgrade -y && \
    dnf install -y vlc && \
    dnf install -y libaacs libbdplus && \
    dnf install -y libbluray-bdj && \
    dnf clean all

USER "vlc"

WORKDIR "/data"

VOLUME ["/data"]

ENTRYPOINT ["/usr/bin/cvlc"]


  


  And then run :

  


  docker run -d -v "d:\path":/data -p 8787:8787 myrepo/myvlc:v1 file:///data/Sample.mkv --sout '#transcode {vcodec=h264,acodec=mp3,samplerate=44100}:std{access=http,mux=ffmpeg{mux=flv},dst=0.0.0.0:8787/stream.flv}'


  


  I get error :

  


  2023-04-04 12:19:11 [000055933c090060] vlcpulse audio output error: PulseAudio server connection failure: Connection refused
2023-04-04 12:19:11 [000055933c09d680] dbus interface error: Failed to connect to the D-Bus session daemon: Unable to autolaunch a dbus-daemon without a $DISPLAY for X11
2023-04-04 12:19:11 [000055933c09d680] main interface error: no suitable interface module
2023-04-04 12:19:11 [000055933bf26ad0] main libvlc error: interface "dbus,none" initialization failed
2023-04-04 12:19:11 [000055933c08d7a0] main interface error: no suitable interface module
2023-04-04 12:19:11 [000055933bf26ad0] main libvlc error: interface "globalhotkeys,none" initialization failed
2023-04-04 12:19:11 [000055933c08d7a0] dummy interface: using the dummy interface module...
2023-04-04 12:19:11 [00007f3b84001250] stream_out_standard stream out error: no mux specified or found by extension
2023-04-04 12:19:11 [00007f3b84000f30] main stream output error: stream chain failed for `standard{mux="",access="",dst="'#transcode"}'
2023-04-04 12:19:11 [00007f3b90000c80] main input error: cannot start stream output instance, aborting
2023-04-04 12:19:11 [00007f3b7c001990] stream_out_standard stream out error: no mux specified or found by extension
2023-04-04 12:19:11 [00007f3b7c001690] main stream output error: stream chain failed for `standard{mux="",access="",dst="'#transcode"}'
2023-04-04 12:19:11 [00007f3b90000c80] main input error: cannot start stream output instance, aborting


  


  I mention that I'm using cvlc and I can't stream that mkv file.

  


  I tried as well --sout '#transcode{scodec=none}:http{mux=ffmpeg{mux=flv},dst=:8787/}' but same errors.

  


  How can I solve it ?