How do i access pixel values of frames in deepstream pipeline

Question

I am using probe to get data to a custom function and I need to access pixel value of the frames. I am trying to average video frames. How do I access it?

gst_pad_add_probe (osd_sink_pad, GST_PAD_PROBE_TYPE_BUFFER, probe_function, NULL, NULL);

I tried to access it using NvDsBatchMeta and GstBuffer but was not able to access it.