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Unable to change video playback speed run-time QMediaplayer QAbstractVideoSurace

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  • SGaistS Offline
    SGaistS Offline
    SGaist
    Lifetime Qt Champion
    wrote on last edited by
    #6

    Can you see any particular changes in the video frame you receive when that happens ?

    Interested in AI ? www.idiap.ch
    Please read the Qt Code of Conduct - https://forum.qt.io/topic/113070/qt-code-of-conduct

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    • SGaistS SGaist

      Can you see any particular changes in the video frame you receive when that happens ?

      M Offline
      M Offline
      magicstar
      wrote on last edited by magicstar
      #7

      @SGaist ,
      The video frame is not displayed at all. As present function is not called. So, I do not see any change in videoframe.
      I am not sure why I am facing many problems with above implementation. I have observed few other problems.

      1. If I stop video or reload second video I get read access violation at
        pixmap->setPixmap(QPixmap::fromImage(img));

      2. I am unable to play video at 4x speed. audio and video is not synced at all. Seems like audio gets played at 4x speed and frames get piled up and are being displayed at its own speed.

      I have implemented QAbstractVideoSurface to modify frames on the fly using different OpenCV functions. Currently, I am facing many problems just at the basic implementation. Is there any other better way to achieve the goal ?

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      • SGaistS Offline
        SGaistS Offline
        SGaist
        Lifetime Qt Champion
        wrote on last edited by
        #8
        1. Did you check the stack trace to see what is happening ?
          Are you sure your pixmap is value ?
          Are creating a new VideoFrameGrabber in between ?
        2. What kind of processing are you applying ? These can be time consuming and thus slow down the video pipeline.

        Interested in AI ? www.idiap.ch
        Please read the Qt Code of Conduct - https://forum.qt.io/topic/113070/qt-code-of-conduct

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        • SGaistS SGaist
          1. Did you check the stack trace to see what is happening ?
            Are you sure your pixmap is value ?
            Are creating a new VideoFrameGrabber in between ?
          2. What kind of processing are you applying ? These can be time consuming and thus slow down the video pipeline.
          M Offline
          M Offline
          magicstar
          wrote on last edited by magicstar
          #9

          @SGaist ,

          1. I tried debug problem through stack trace.
            The read access violation is for QScrollBar::wheelEvent function of file Qt5Widgetsd.
            I tried disabling QGraphicsView and pixmap event filter by setEnabled(false). But, it did not help.
            I am not creating new VideoFrameGrabber in between. Also, there is no problem in QImage as i am able to save image.
          2. Currently, I am not applying any processing. Just converting QVideoFrame To QImage
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          • SGaistS Offline
            SGaistS Offline
            SGaist
            Lifetime Qt Champion
            wrote on last edited by
            #10

            Where do you have scrollbars in your application ?
            What is the input format ?

            Interested in AI ? www.idiap.ch
            Please read the Qt Code of Conduct - https://forum.qt.io/topic/113070/qt-code-of-conduct

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            • SGaistS SGaist

              Where do you have scrollbars in your application ?
              What is the input format ?

              M Offline
              M Offline
              magicstar
              wrote on last edited by
              #11

              @SGaist
              After lot of digging and modying code, I feel the problem is not with the scrollbars. After I stop the media, QGraphicsView *view seems to be deleted and that is why i get access violation error. However, I wonder if resources are deallocated when QAbstractVideoSurface::stop is called?
              If so, what is the better way of implementing the functionality ?

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              • SGaistS Offline
                SGaistS Offline
                SGaist
                Lifetime Qt Champion
                wrote on last edited by
                #12

                It should not...

                Can you show the stack trace of the crash ?

                Interested in AI ? www.idiap.ch
                Please read the Qt Code of Conduct - https://forum.qt.io/topic/113070/qt-code-of-conduct

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                • SGaistS SGaist

                  It should not...

                  Can you show the stack trace of the crash ?

                  M Offline
                  M Offline
                  magicstar
                  wrote on last edited by magicstar
                  #13
                  This post is deleted!
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                  • SGaistS SGaist

                    It should not...

                    Can you show the stack trace of the crash ?

                    M Offline
                    M Offline
                    magicstar
                    wrote on last edited by
                    #14

                    @SGaist
                    Stack trace of the crash did help me with the error. Thanks a lot...
                    However, one error still remains. Present function of the QAbstractVideoSurface is not called sometimes. And this behaviour is very random as of now.

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                    • SGaistS Offline
                      SGaistS Offline
                      SGaist
                      Lifetime Qt Champion
                      wrote on last edited by
                      #15

                      What was it ?

                      Interested in AI ? www.idiap.ch
                      Please read the Qt Code of Conduct - https://forum.qt.io/topic/113070/qt-code-of-conduct

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