shithub: libvpx

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vp8: Limit Q change for screen content CBR mode

Add last_q[] to layer context, and add limit on
Q change from previous layer/frame. For now put
hard limit of 12 for decrease.

For 1 pass CBR sreen content mode.

Change-Id: Ifb972c9b6831440c80b1cb07a054c577ece930ec

--- a/vp8/encoder/onyx_if.c

+++ b/vp8/encoder/onyx_if.c

@@ -218,6 +218,8 @@

   lc->frames_since_last_drop_overshoot = cpi->frames_since_last_drop_overshoot;

   lc->force_maxqp = cpi->force_maxqp;

   lc->last_frame_percent_intra = cpi->last_frame_percent_intra;

+  lc->last_q[0] = cpi->last_q[0];

+  lc->last_q[1] = cpi->last_q[1];

   memcpy(lc->count_mb_ref_frame_usage, cpi->mb.count_mb_ref_frame_usage,

          sizeof(cpi->mb.count_mb_ref_frame_usage));

@@ -255,6 +257,8 @@

   cpi->frames_since_last_drop_overshoot = lc->frames_since_last_drop_overshoot;

   cpi->force_maxqp = lc->force_maxqp;

   cpi->last_frame_percent_intra = lc->last_frame_percent_intra;

+  cpi->last_q[0] = lc->last_q[0];

+  cpi->last_q[1] = lc->last_q[1];

   memcpy(cpi->mb.count_mb_ref_frame_usage, lc->count_mb_ref_frame_usage,

          sizeof(cpi->mb.count_mb_ref_frame_usage));

--- a/vp8/encoder/onyx_int.h

+++ b/vp8/encoder/onyx_int.h

@@ -257,6 +257,7 @@

   int count_mb_ref_frame_usage[MAX_REF_FRAMES];

+  int last_q[2];

 } LAYER_CONTEXT;

 typedef struct VP8_COMP {

--- a/vp8/encoder/ratectrl.c

+++ b/vp8/encoder/ratectrl.c

@@ -1125,6 +1125,14 @@

   }

 }

+static int limit_q_cbr_inter(int last_q, int current_q) {

+  int limit_down = 12;

+  if (last_q - current_q > limit_down)

+    return (last_q - limit_down);

+  else

+    return current_q;

+}

+

 int vp8_regulate_q(VP8_COMP *cpi, int target_bits_per_frame) {

   int Q = cpi->active_worst_quality;

@@ -1263,6 +1271,12 @@

       }

     }

   }

+

+  // Limit decrease in Q for 1 pass CBR screen content mode.

+  if (cpi->common.frame_type != KEY_FRAME && cpi->pass == 0 &&

+      cpi->oxcf.end_usage == USAGE_STREAM_FROM_SERVER &&

+      cpi->oxcf.screen_content_mode)

+    Q = limit_q_cbr_inter(cpi->last_q[1], Q);

   return Q;

 }