shithub: libvpx

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Modify active_worst_quality setting for one pass CBR.

Current setting had active_worst_quality set too high (close to worst_quality)
for first frame(s) following first key frame. This changes that to be somewhat
more aggressive in allowing active_worst_quality to be lower following key frame.

Also remove the 4/5 reduction in active_worst for key frame as
this should be set by the user qp_max setting.

Change-Id: I0530b3ddcc85c00e3eb7568de1b14a31206c4a4c

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

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

@@ -563,18 +563,23 @@

   const VP9_COMMON *const cm = &cpi->common;

   const RATE_CONTROL *rc = &cpi->rc;

   // Buffer level below which we push active_worst to worst_quality.

-  int64_t critical_level = rc->optimal_buffer_level >> 2;

+  int64_t critical_level = rc->optimal_buffer_level >> 3;

   int64_t buff_lvl_step = 0;

   int adjustment = 0;

   int active_worst_quality;

+  int ambient_qp;

   if (cm->frame_type == KEY_FRAME)

-    return rc->worst_quality * 4 / 5;

-  if (cm->current_video_frame > 1)

-    active_worst_quality = MIN(rc->worst_quality,

-                               rc->avg_frame_qindex[INTER_FRAME] * 5 / 4);

-  else

-    active_worst_quality = MIN(rc->worst_quality,

-                               rc->avg_frame_qindex[KEY_FRAME] * 3 / 2);

+    return rc->worst_quality;

+  // For ambient_qp we use minimum of avg_frame_qindex[KEY_FRAME/INTER_FRAME]

+  // for the first few frames following key frame. These are both initialized

+  // to worst_quality and updated with (3/4, 1/4) average in postencode_update.

+  // So for first few frames following key, the qp of that key frame is weighted

+  // into the active_worst_quality setting.

+  ambient_qp = (cm->current_video_frame < 5) ?

+      MIN(rc->avg_frame_qindex[INTER_FRAME], rc->avg_frame_qindex[KEY_FRAME]) :

+      rc->avg_frame_qindex[INTER_FRAME];

+  active_worst_quality = MIN(rc->worst_quality,

+                             ambient_qp * 5 / 4);

   if (rc->buffer_level > rc->optimal_buffer_level) {

     // Adjust down.

     // Maximum limit for down adjustment, ~30%.

@@ -592,12 +597,11 @@

     if (critical_level) {

       buff_lvl_step = (rc->optimal_buffer_level - critical_level);

       if (buff_lvl_step) {

-        adjustment =

-            (int)((rc->worst_quality - rc->avg_frame_qindex[INTER_FRAME]) *

-                  (rc->optimal_buffer_level - rc->buffer_level) /

-                  buff_lvl_step);

+        adjustment = (int)((rc->worst_quality - ambient_qp) *

+                           (rc->optimal_buffer_level - rc->buffer_level) /

+                           buff_lvl_step);

       }

-      active_worst_quality = rc->avg_frame_qindex[INTER_FRAME] + adjustment;

+      active_worst_quality = ambient_qp + adjustment;

     }

   } else {

     // Set to worst_quality if buffer is below critical level.

--- a/vp9/encoder/vp9_svc_layercontext.c

+++ b/vp9/encoder/vp9_svc_layercontext.c

@@ -77,6 +77,7 @@

       lc->target_bandwidth = oxcf->ts_target_bitrate[layer];

       lrc->last_q[INTER_FRAME] = oxcf->worst_allowed_q;

       lrc->avg_frame_qindex[INTER_FRAME] = oxcf->worst_allowed_q;

+      lrc->avg_frame_qindex[KEY_FRAME] = oxcf->worst_allowed_q;

     } else {

       lc->target_bandwidth = oxcf->ss_target_bitrate[layer];

       lrc->last_q[KEY_FRAME] = oxcf->best_allowed_q;

-- 

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