shithub: libvpx

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Enable dual arf with constant q.

Add second level arf Q adjustment when using dual arfs
in constant Q mode.

Previously in constant Q mode enabling dual arf hurt by ~5%
but with this change the average benefit is ~1-1.5% with some
mid range data points up ~10%.

Note however that it still hurts on some clips including
some very low motion show content.

Change-Id: I5b7789a2f42a6127d9e801cc010c20a7113bdd9b

--- a/vp9/encoder/vp9_encoder.c

+++ b/vp9/encoder/vp9_encoder.c

@@ -3417,7 +3417,7 @@

   // Note that at the moment multi_arf is only configured for 2 pass VBR and

   // will not work properly with svc.

   if ((oxcf->pass == 2) && !cpi->use_svc &&

-      (cpi->oxcf.enable_auto_arf > 1) && (cpi->oxcf.rc_mode == VPX_VBR))

+      (cpi->oxcf.enable_auto_arf > 1))

     cpi->multi_arf_allowed = 1;

   else

     cpi->multi_arf_allowed = 0;

--- a/vp9/encoder/vp9_ratectrl.c

+++ b/vp9/encoder/vp9_ratectrl.c

@@ -971,7 +971,13 @@

       if (!cpi->refresh_alt_ref_frame) {

         active_best_quality = cq_level;

       } else {

-        active_best_quality = get_gf_active_quality(rc, q, cm->bit_depth);

+       const GF_GROUP *const gf_group = &cpi->twopass.gf_group;

+       active_best_quality = get_gf_active_quality(rc, q, cm->bit_depth);

+

+        // Modify best quality for second level arfs. For mode VPX_Q this

+        // becomes the baseline frame q.

+        if (gf_group->rf_level[gf_group->index] == GF_ARF_LOW)

+          active_best_quality = (active_best_quality + cq_level + 1) / 2;

       }

     } else {

       active_best_quality = get_gf_active_quality(rc, q, cm->bit_depth);