QT5.3.2 quick camera

I have a question. I use the Qt5.3.2 the arm environment is imxSABRE6Q .the GStreamer version is 1.0 src：imxv4l2src sink：imxeglvivsink . 1. when start camera, the screen only a frame . 2. then I trigger event that the camera stop. Then I again trigger one event ,the camera start working is OK, but after about 30s the screen display video stop . I need some suggestion about it. Thanks