shithub: libvpx

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Speed-up recode loop for extreme bitrate diffs

Adjusts the q adjustement step depending on how far the
projected and target rates differ.

Change-Id: I498d03523ca233a270512ca3972c372daa4ca2a8

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

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

@@ -3216,6 +3216,13 @@

   vpx_clear_system_state();

 }

+#define MAX_QSTEP_ADJ 4

+static int get_qstep_adj(int rate_excess, int rate_limit) {

+  int qstep =

+      rate_limit ? ((rate_excess + rate_limit / 2) / rate_limit) : INT_MAX;

+  return VPXMIN(qstep, MAX_QSTEP_ADJ);

+}

+

 static void encode_with_recode_loop(VP9_COMP *cpi, size_t *size,

                                     uint8_t *dest) {

   VP9_COMMON *const cm = &cpi->common;

@@ -3389,6 +3396,7 @@

         // to attempt to recode.

         int last_q = q;

         int retries = 0;

+        int qstep;

         if (cpi->resize_pending == 1) {

           // Change in frame size so go back around the recode loop.

@@ -3414,7 +3422,10 @@

             q_high = rc->worst_quality;

           // Raise Qlow as to at least the current value

-          q_low = q < q_high ? q + 1 : q_high;

+          qstep =

+              get_qstep_adj(rc->projected_frame_size, rc->this_frame_target);

+          q_low = VPXMIN(q + qstep, q_high);

+          // q_low = q < q_high ? q + 1 : q_high;

           if (undershoot_seen || loop_at_this_size > 1) {

             // Update rate_correction_factor unless

@@ -3439,7 +3450,10 @@

           overshoot_seen = 1;

         } else {

           // Frame is too small

-          q_high = q > q_low ? q - 1 : q_low;

+          qstep =

+              get_qstep_adj(rc->this_frame_target, rc->projected_frame_size);

+          q_high = VPXMAX(q - qstep, q_low);

+          // q_high = q > q_low ? q - 1 : q_low;

           if (overshoot_seen || loop_at_this_size > 1) {

             vp9_rc_update_rate_correction_factors(cpi);