Something

    /* mark buffers and put on caps */
    caps = gst_caps_new_simply ("video/x-theora", "width", G_TYPE_INT, enc->width, "height", G_TYPE_INT, enc->height, "framerate", GST_TYPE_FRACTION, enc->fps_n, enc->fps_d, "pixel-aspect-ratio", GST_TYPE_FRACTION, enc->par_n, enc->par_d, NULL)
    caps = theora_set_header_on_caps (caps, buffers);
    GST_DEBUG ("here are the caps: %" GST_PTR_FORMAT, caps);
    gst_pad_set_caps (enc->srcpad, caps);