Gstreamer: what happens with frame buffer memory that is passed into appsink and used in OpenCV Mat?

Question

I'm reading videoframe in appsink into opencv Mat:

GstFlowReturn GStreamPipeline::new_sample(GstElement* sink, GStreamPipeline* gsp) {
    GstSample* sample;

    /* Retrieve the buffer */
    g_signal_emit_by_name(sink, "pull-sample", &sample);
    if (sample) 
    {

        GstBuffer* buffer = gst_sample_get_buffer(sample);
        GstSegment* segment = gst_sample_get_segment(sample);
        GstCaps* current_caps = gst_pad_get_current_caps(gst_element_get_static_pad(gsp->app_sink, "sink"));
        GstStructure* new_pad_struct = gst_caps_get_structure(current_caps, 0);
        gint width = 0, height = 0;
        if (!gst_structure_get_int(new_pad_struct, "width", &width) ||
            !gst_structure_get_int(new_pad_struct, "height", &height)) {
            g_print("No width/height available\n");
        }

        GstMapInfo map;
        gst_buffer_map(buffer, &map, GST_MAP_READ);

        cv::Mat frame(cv::Size(width, height), CV_8UC3, (char*)map.data);
        gst_buffer_unmap(buffer, &map);
        if (!current_caps) gst_caps_unref(current_caps);
        gst_sample_unref(sample);
        return GST_FLOW_OK;
    }

    return GST_FLOW_ERROR;
}

What happens with memory to which frame.data points after I leave the scope of the function? How long does that buffer exists? Do I need to copy it to be safe? I want to understand its lifetime to avoid unnecessary copy.

Answer 1

Figured that, need to use gst_buffer_ref(buffer) to increase ref count.