videorate: need implement prepare_output_buffer()

As videorate will ref input buffer, the input isn't writable. Below function will call gst_buffer_copy() which will cause issue when HW need fixed memory. Do we need implement prepare_output_buffer() in videorate?

static GstFlowReturn
default_prepare_output_buffer (GstBaseTransform * trans,
    GstBuffer * inbuf, GstBuffer ** outbuf)
{

  /* no pool, we need to figure out the size of the output buffer first */
  if ((bclass->transform_ip != NULL) && priv->always_in_place) {
    /* we want to do an in-place alloc */
    if (gst_buffer_is_writable (inbuf)) {
      GST_DEBUG_OBJECT (trans, "inplace reuse writable input buffer");
      *outbuf = inbuf;
    } else {
      GST_DEBUG_OBJECT (trans, "making writable buffer copy");
      /* we make a copy of the input buffer */
      *outbuf = **gst_buffer_copy **(inbuf);
    }
    goto done;
  }


}