Keep Checking for Live Video Stream

VIDYUL SHAH

Hello Community,
I'm currently facing an issue with my program's ability to continuously check for a live video stream from my server. At present, when the program starts, it checks if there's a stream available from a given URL. If not, it displays an error indicating that the media is stopped. However, once I connect my Ethernet cable, it fails to recognize and restart the media stream. It also doesn't continue to check if the URL is streaming the video.
How can I modify my current code to address this? What additions should I make to ensure it continuously checks for the stream and displays an error until the live video stream starts?
Here is my code:

#!/usr/bin/env python3

import os, sys, time
from PyQt5 import QtWidgets, QtCore
from PyQt5.QtCore import QLibraryInfo, pyqtSignal, pyqtSlot, QUrl, QTimer, QTime, QDate, QThread
from PyQt5.QtWidgets import QDialog, QApplication, QMainWindow
from PyQt5.uic import loadUi
from PyQt5.QtGui import QImage
from PyQt5.QtMultimedia import QMediaPlayer, QMediaContent

os.environ["QT_QPA_PLATFORM_PLUGIN_PATH"] = QLibraryInfo.location(
    QLibraryInfo.PluginsPath
)

class VideoStream(QDialog):
    ImageUpdate = pyqtSignal(QImage)
    
    def __init__(self):
        super(VideoStream, self).__init__()
        loadUi('VideoStream.ui', self)
        try:
            self.media_player = QMediaPlayer(None, QMediaPlayer.VideoSurface)
            self.media_player.setVideoOutput(self.video_label)

            media_content = QMediaContent(QUrl("rtsp://127.0.0.1:5000/test"))
            self.media_player.setMedia(media_content)

            self.timer = QTimer(self)
            #self.timer.timeout.connect(self.update_video_label)
            self.timer.start(0)  # Set the update interval in milliseconds

            self.media_player.stateChanged.connect(self.on_state_changed)
            self.media_player.play()
        except Exception as e:
            print(e)
        
        
    def on_state_changed(self, state):
        if state == QMediaPlayer.StoppedState:
            print("Media player stopped")

if __name__=='__main__':
    app=QApplication(sys.argv)
    mainwindow=VideoStream()
    widget=QtWidgets.QStackedWidget()
    widget.addWidget(mainwindow)
    widget.show()
    app.exec_()

Case 1 - Output when initially I don't connect the Ethernet cable and start the UI:
Media player stopped
Error: "Could not open resource for reading and writing."
Case 2 - Output when I connect the Ethernet cable and then start the UI and at later stage remove the Ethernet Cable and Plug it Again (But in this case the streaming doesn't start again):
Warning: "Error sending UDP packets"
Warning: "Error sending UDP packets"
Warning: "Error sending UDP packets"
Media player stopped
Error: "Could not read from resource."

VIDYUL SHAH

@JonB This what I have written. I have to put a label giving the status of video sream connected or disconnected. According to current logic it labelsetText switches between connected and disconnected. Is there any other kind of logic that could be used and this problem also is solved.

class VideoStream(QDialog):
    ImageUpdate = pyqtSignal(QImage)
    
    def __init__(self):
        super(VideoStream, self).__init__()
        loadUi('VideoStream.ui', self)
        self.media_url = "rtsp://127.0.0.1:5000/test"
        self.initialize_media_player()
    def initialize_media_player(self):
        try:
            self.media_player = QMediaPlayer(None, QMediaPlayer.VideoSurface)
            self.media_player.setVideoOutput(self.video_label)
            media_content = QMediaContent(QUrl(self.media_url))
            self.media_player.setMedia(media_content)

            self.timer = QTimer(self)
            self.timer.timeout.connect(self.check_stream)
            self.timer.start(10)  # Check stream every second

            self.media_player.stateChanged.connect(self.on_state_changed)
            self.media_player.play()
        except Exception as e:
            print(e)
        
    def check_stream(self):
        if self.media_player.state() == QMediaPlayer.StoppedState:
            self.initialize_media_player()
    
    def on_state_changed(self, state):
        if state == QMediaPlayer.PlayingState:
            print("Media player Playing")
        else:
            print("Media player stopped")

SGaist

Hi,

You are breaking the connection so you have to establish a new one. One possible thing you can do is to start a timer 9n failure and try to restart the media player using an exponential value for the timer as there's no need to spam the connection if the network is down.

VIDYUL SHAH

@SGaist Didn't understand this timer concept. Could you explain this please

VIDYUL SHAH

@SGaist Basically I want to do is error handling that is the connection is established or not established so it will keel checking for connection and display error message until the connection is established.
I tried to use enum QMediaPlayer::Error , enum QMediaPlayer::MediaStatus and enum QMediaPlayer::State but no luck in finding the appropriate solution

JonB

@VIDYUL-SHAH
If you want to "keep checking something" then as @SGaist suggested you should use a QTimer to repeatedly try that (establishing connection). I don't think you get a signal for "Ethernet cable plugged in/network available". And then he also suggested to adjust the time on the timer so that it does not re-fire too rapidly.

JoeCFD

@VIDYUL-SHAH I guess Qt Multimedia may not have the mechanism to check if streaming is running or stopped.

Onvif is a tool to detect which URLs are available in the network. Nowadays, I guess all cameras are onvif compatible.

If you use gstreamer, you can check the gap of two coming frames with a timer. If the gap is more than a few seconds(you decide, 2, 3, or 4s), it can mean streaming is broken.

FFmpeg may have similar function.

VIDYUL SHAH

@JonB https://doc.qt.io/qt-5/qmediaplayer.html#setMedia
I got this link from one of the qt forum where I read on gstreamer. SO what I have done is that from one of my pc the video data is coming as a gstreamed data at url ''rtsp://127.0.0.1:5000/test". Do I need to directly use this link or should I write gstream pile? Then I also read to keep listening for the mediaStatusChanged() and error() signals. How can I use these to check if the streaming is stopped or not using "start a timer 9n failure and try to restart the media player" that you suggested . Could you please elaborate.
To be honest I just copied this

def on_state_changed(self, state):
       if state == QMediaPlayer.StoppedState:
           print("Media player stopped")

from one of the github repo but didn't understand how it works.
@JoeCFD as you suggested, is it possible to check check gaps in frames could you share some links please. I couldn't find any related stuff. Maybe I searched the wrong way.

JonB

@VIDYUL-SHAH said in Keep Checking for Live Video Stream:

using "start a timer 9n failure and try to restart the media player" that you suggested

That was @SGaist. Anyway, he suggests connect a slot to QMediaPlayer.error() signal. In the slot set off a QTimer.singleShot() which does a self.media_player.play() (or maybe the self.media_player.setMedia(media_content) again too, I don't know), probably with increasing values for the single shot timeout so it does not fire too often. That is the gist, obviously you need to cease to do this after (a) the player has started successfully in case it then gets a later error or (b) a certain amount of time has expired without success, else you will be doing this forever.

JoeCFD

@VIDYUL-SHAH take a look at the source code of qgroundcontrol for this.

VIDYUL SHAH

@JoeCFD Ty for the suggestion but it went all over my head. Except a few lines, I couldn't understand the rest as it is a very big code.
Just keeping the link here if someone reading this thread might want to get help from it.
https://github.com/mavlink/qgroundcontrol/blob/master/src/VideoReceiver/GstVideoReceiver.cc
@JonB @SGaist Sorry for that, actually after reading all suggestions and trying to reply all of them, confused me.

VIDYUL SHAH

@JonB This what I have written. I have to put a label giving the status of video sream connected or disconnected. According to current logic it labelsetText switches between connected and disconnected. Is there any other kind of logic that could be used and this problem also is solved.

class VideoStream(QDialog):
    ImageUpdate = pyqtSignal(QImage)
    
    def __init__(self):
        super(VideoStream, self).__init__()
        loadUi('VideoStream.ui', self)
        self.media_url = "rtsp://127.0.0.1:5000/test"
        self.initialize_media_player()
    def initialize_media_player(self):
        try:
            self.media_player = QMediaPlayer(None, QMediaPlayer.VideoSurface)
            self.media_player.setVideoOutput(self.video_label)
            media_content = QMediaContent(QUrl(self.media_url))
            self.media_player.setMedia(media_content)

            self.timer = QTimer(self)
            self.timer.timeout.connect(self.check_stream)
            self.timer.start(10)  # Check stream every second

            self.media_player.stateChanged.connect(self.on_state_changed)
            self.media_player.play()
        except Exception as e:
            print(e)
        
    def check_stream(self):
        if self.media_player.state() == QMediaPlayer.StoppedState:
            self.initialize_media_player()
    
    def on_state_changed(self, state):
        if state == QMediaPlayer.PlayingState:
            print("Media player Playing")
        else:
            print("Media player stopped")

JonB

@VIDYUL-SHAH
Well, it's in the right direction. The important thing is: did it help? Do the retries end up working such that it starts working when " I connect my Ethernet cable", which is what you wanted?

VIDYUL SHAH

@JonB Yes it starts but I notice after keeping ethernet unplugged for a long time. It gives warning messages 3-4 (Warning: "Error sending UDP packets") times in an interval as specified in QTimer. Ans then it will start the recurrsion and keep checking for the connection until I again plug-in the ethernet. Is there any way to reduce this time apart from setting the qtimer and another query is that for the connection/disconnection label which i asked previously.

JonB

@VIDYUL-SHAH
I can't say about the UDP packets sending errors. We previously said you might increase the timer timeout (perhaps exponentially) each time it fails so as to reduce the attempts by not hammering it while it is failing/cable is unplugged. I don't know/understand if you have a query about a label, you can set a label to whatever whenever you want.

I have to say I think it is "unusual" to try to cater automatically for "ethernet unplugged" or similar. If Url is unavailable it's unavailable, I would expect user to retry and/or change Url. But that's up to you.

And just btw self.timer.start(10) # Check stream every second is not every second, it's 100 times per second. Which is "hammering" and seems way too frequent. But if you implement the "exponential timeout increase" that will also alter that, though you should be aware of the units QTimer works on.

Oh, and unless you find you have to do it, I wouldn't recreate a new QMediaPlayer (and a QTimer for that matter) every time. Isn't it enough to just call self.media_player.play() on each timeout?

VIDYUL SHAH

@JonB @SGaist I was playing with:

def initialize_media_player(self):
        self.media_player = QMediaPlayer(None, QMediaPlayer.VideoSurface)
        media_content = QMediaContent(QUrl(self.media_url))
        self.media_player.setMedia(media_content)
        self.media_player.setVideoOutput(self.video_label)
        
        self.check_stream()

        '''self.timer = QTimer(self)
        self.timer.timeout.connect(self.check_stream)
        self.timer.start(5)  # Check stream every second '''

        self.media_player.stateChanged.connect(self.on_state_changed)
        self.media_player.play()

def check_stream(self):
        if self.media_player.mediaStatus() == QMediaPlayer.UnknownMediaStatus:
            print('1')
        if self.media_player.mediaStatus() == QMediaPlayer.NoMedia:
            print('2')
        if self.media_player.mediaStatus() == QMediaPlayer.LoadingMedia:
            print('3')
        if self.media_player.mediaStatus() == QMediaPlayer.LoadedMedia:
            print('4')
        if self.media_player.mediaStatus() == QMediaPlayer.StalledMedia:
            print('5')
        if self.media_player.mediaStatus() == QMediaPlayer.BufferingMedia:
            print('6')
        if self.media_player.mediaStatus() == QMediaPlayer.BufferedMedia:
            print('7')
        if self.media_player.mediaStatus() == QMediaPlayer.EndOfMedia:
            print('8')
        if self.media_player.mediaStatus() == QMediaPlayer.InvalidMedia:
            print('9')

What I did was I ran my user interface (UI) on one computer without executing the Python script on another computer to stream live video. This resulted in the following output on the screen:

3
Error: "Could not open resource for reading and writing."

Then, I simply uncommented the timer section without executing the Python script on the other computer to stream the live video. This resulted in the following output on the screen:

3
9
9
9
9
9
..... (continuously)

Later, I ran my UI on one computer while also running the Python script on the other computer to stream live video. This resulted in the following output on the screen:

3
7
7
7
7
7
..... (continuously)

Now what I have understood is that using a few lines from 'def check_stream(self)' I have to build a logic which will check if the data is streamed from the URL or is the streaming has stopped and then wait for a few seconds to again play the media but I am unable to build this logic and also unable to understand when and how to catch these lines from self.media_player.play().

VIDYUL SHAH

@JonB Thank you for all the inputs, I somehow managed to play and stop the video and also display error message.