+/* Completely arbitrary. Ratecontrol lowers relative quality at higher framerates
+ * and the reverse at lower framerates; this serves as the center of the curve.
+ * Halve all the values for frame-packed 3D to compensate for the "doubled"
+ * framerate. */
+#define BASE_FRAME_DURATION (0.04f / ((h->param.i_frame_packing == 5)+1))
+
+/* Arbitrary limitations as a sanity check. */
+#define MAX_FRAME_DURATION (1.00f / ((h->param.i_frame_packing == 5)+1))
+#define MIN_FRAME_DURATION (0.01f / ((h->param.i_frame_packing == 5)+1))
+
+#define CLIP_DURATION(f) x264_clip3f(f,MIN_FRAME_DURATION,MAX_FRAME_DURATION)
+