shithub: libvpx

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Speed setting correction to max q estimate.

Use a crude correction factor to correct for
lower compression efficiency at higher encode
speeds when estimating the max Q for the
clip.

Change-Id: I5ae377647f4adf5e91d700a8791fb3b8f70efc73

--- a/vp9/encoder/vp9_firstpass.c

+++ b/vp9/encoder/vp9_firstpass.c

@@ -911,6 +911,7 @@

   const double section_err = fpstats->coded_error / fpstats->count;

   const double err_per_mb = section_err / num_mbs;

+  const double speed_term = 1.0 + ((double)cpi->speed * 0.04);

   if (section_target_bandwitdh <= 0)

     return rc->worst_quality;          // Highest value allowed

@@ -924,8 +925,8 @@

   for (q = rc->best_quality; q < rc->worst_quality; ++q) {

     const double err_correction_factor = calc_correction_factor(err_per_mb,

                                              ERR_DIVISOR, 0.5, 0.90, q);

-    const int bits_per_mb_at_this_q = vp9_rc_bits_per_mb(INTER_FRAME, q,

-                                                         err_correction_factor);

+    const int bits_per_mb_at_this_q =

+      vp9_rc_bits_per_mb(INTER_FRAME, q, (err_correction_factor * speed_term));

     if (bits_per_mb_at_this_q <= target_norm_bits_per_mb)

       break;

   }

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

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

@@ -1010,7 +1010,7 @@

         *frame_over_shoot_limit  = this_frame_target * 9 / 8;

         *frame_under_shoot_limit = this_frame_target * 7 / 8;

       } else {

-        // Stron overshoot limit for constrained quality

+        // Strong overshoot limit for constrained quality

         if (cpi->oxcf.end_usage == USAGE_CONSTRAINED_QUALITY) {

           *frame_over_shoot_limit  = this_frame_target * 11 / 8;

           *frame_under_shoot_limit = this_frame_target * 2 / 8;