L2E: Use libvpx's default q in case of invalid external value

If the external model recommends an invalid q value, we use the
default q selected by libvpx's rate control strategy.

We update the test so that when the external model wants to control
GOP decision, it could get per frame information and just recommend
an invalid q.

Change-Id: I69be4b0ee0800e7ab0706d305242bb87f001b1f7

1 files changed, 9 insertions, 0 deletions

diff --git a/vpx/vpx_ext_ratectrl.h b/vpx/vpx_ext_ratectrl.h
index 6e41abaf4..b57148c69 100644
--- a/vpx/vpx_ext_ratectrl.h
+++ b/vpx/vpx_ext_ratectrl.h
@@ -48,11 +48,20 @@ typedef enum vpx_rc_type {
  */
 typedef void *vpx_rc_model_t;
 
+/*!\brief A reserved value for the q index.
+ * If the external rate control model returns this value,
+ * the encoder will use the default q selected by libvpx's rate control
+ * system.
+ */
+#define VPX_DEFAULT_Q -1
+
 /*!\brief Encode frame decision made by the external rate control model
  *
  * The encoder will receive the decision from the external rate control model
  * through get_encodeframe_decision() defined in vpx_rc_funcs_t.
  *
+ * If q_index = VPX_DEFAULT_Q, the encoder will use libvpx's default q.
+ *
  * If max_frame_size = 0, the encoding ignores max frame size limit.
  * If max_frame_size = -1, the encoding uses VP9's max frame size as the limit.
  * If the encoded frame size is larger than max_frame_size, the frame is