RTSP stream delay which live stream a ip camera

[greed_14]

Hello, I've been using Qt 6.3.1 for RTSP IP camera streaming. However, I've noticed a delay of approximately 3-4 seconds in the streaming process. Interestingly, when I perform the same streaming using Qt 5.15.2, there is no such delay. I am aware that Qtmultimeadia module has undergone modifications since Qt 6. Is there a way to eliminate this streaming delay? Additionally, there are instances when the delay isn't observed, I am getting a Warning: "A lot of buffers are being dropped." and video is getting struck

Item {

MediaPlayer {
    id: player
    source: "rtsp://admin:admin123@192.168.1.108:554/cam/realmonitor?channel=1&subtype=0"
    videoOutput:  cameraout
    onPlaybackStateChanged: function(newState) {
        console.log("playback state changed",playbackState)
    }
    onErrorOccurred: function(error, errorString) {
        console.log("error occured ",error, errorString);
    }
    audioOutput: AudioOutput {
        id: audioOutput
    }
    onHasVideoChanged: {
        console.log("has video changed ",hasVideo);

    }
    onBufferProgressChanged: {
        console.log("buffer changed ",bufferProgress,player.bufferedTimeRange())
    }
    onVideoOutputChanged: {
        console.log("videoOutPut changed",error,errorString,hasVideo,source)
    }
    onMediaStatusChanged: {
        if(player.mediaStatus ==MediaPlayer.NoMedia){
            console.log("onMediaStatusChanged NoMedia",player.mediaStatus,MediaPlayer.NoMedia)
        }
        if(player.mediaStatus ==MediaPlayer.LoadingMedia){
            console.log("onMediaStatusChanged LoadingMedia",player.mediaStatus,MediaPlayer.LoadingMedia)

        }
        if(player.mediaStatus ==MediaPlayer.LoadedMedia){
            console.log("onMediaStatusChanged LoadedMedia",player.mediaStatus,MediaPlayer.LoadedMedia)

        }
        if(player.mediaStatus ==MediaPlayer.BufferingMedia){
            console.log("onMediaStatusChanged BufferingMedia",player.mediaStatus,MediaPlayer.BufferingMedia)

        }
        if(player.mediaStatus ==MediaPlayer.StalledMedia){
            console.log("onMediaStatusChanged StalledMedia",player.mediaStatus,MediaPlayer.StalledMedia)

        }
        if(player.mediaStatus ==MediaPlayer.BufferedMedia){
            console.log("onMediaStatusChanged BufferedMedia",player.mediaStatus,MediaPlayer.BufferedMedia)

        }
        if(player.mediaStatus ==MediaPlayer.EndOfMedia){
            console.log("onMediaStatusChanged EndOfMedia",player.mediaStatus,MediaPlayer.EndOfMedia)

        }
        if(player.mediaStatus ==MediaPlayer.InvalidMedia){
            console.log("onMediaStatusChanged InvalidMedia",player.mediaStatus,MediaPlayer.InvalidMedia)

        }
    }
    onPlaybackRateChanged: {
        console.log("onPlaybackRateChanged ",player.playbackRate)
    }
    onPositionChanged: {
        console.log("onPositionChanged ",player.position)
    }
    onSourceChanged: {
        console.log("onSourceChanged ",player.source)
    }

}


VideoOutput {
    id: cameraout
    anchors.fill:parent
}

Rectangle{
    id: playrect
    width: 100
    height:width
    color: "green"
    anchors.bottom: parent.bottom
    anchors.left: parent.left
    MouseArea{
        anchors.fill: parent
        onClicked: {
            player.source ="rtsp://admin:admin123@192.168.1.108:554/cam/realmonitor?channel=1&subtype=0"
            player.play()
            console.log("play clicked")
        }
    }
}
Rectangle{
    id: pauserect
    width: 100
    height:width
    color: "red"
    anchors.bottom: parent.bottom
    anchors.right: parent.right
    MouseArea{
        anchors.fill: parent
        onClicked: {
            player.source = ""
            player.stop()
            console.log("stopped")
        }
    }
}

}

[JoeCFD]

@greed_14 https://forum.qt.io/topic/148589/mediaplayer-does-not-receive-stream-metadata/3?_=1693329743288

[greed_14]

@JoeCFD i did go through that link but there is nothing about delay in there.

[JoeCFD]

@greed_14 I would upgrade Qt to 6.5 or above first.

[greed_14]

@JoeCFD yea but i need to get it done in Qt 6.3.1 as that's the requirement on the project i am working on.

[JoeCFD]

@greed_14 If your OS is Linux, it is likely gstreamer is applied in Qt(guess) and maybe playbin is used for RTSP streaming. If my guess is correct, playbin has 2s delay by default. You can try it out from command line.

command is:
gst-launch-1.0 playbin -v uri=rtsp://admin:admin123@192.168.1.108:554/cam/realmonitor?channel=1&subtype=0

Since Qt does not offer enough controls over the pipelines, I do not use Qt multimedia module. Instead, I use raw gstreamer code with qml sink for rstp streaming in Linux.

From SGaist in the link above: As Qt 6.5 switched the multimedia backend to ffmpeg.

[greed_14]

@JoeCFD Hi as you have suggested there seems to be a delay with playbin.

command 1:
gst-launch-1.0 playbin -v uri=rtsp://127.0.0.1:8554/cam

when i run the above command 1 which contains playbin there seems to be a 2-3s seconds delay.

command 2:
gst-launch-1.0 rtspsrc location="rtsp://127.0.0.1:8554/cam" latency=10 ! decodebin ! autovideosink

whereas if i run command 2 there's not much visible delay.

I have also been looking for alternative ways instead of using Qtmultimedia module cause there seems to be other issues related to memory with my version.Do you have any example or how i can use use raw gstreamer code with qml sink for rstp streaming without using Qtmultimedia module.

[JoeCFD]

@greed_14 https://github.com/GStreamer/gst-plugins-good/tree/master/tests/examples/qt/qmlsink

in your command 2, you added 10ms delay which is too small for you to see any effect.