[x265] [PATCH 3/3]SBRC: Tune ratefactor for simple/complex frames based on segment average

[Kirithika Kalirathnam]

From fd5e47885c1b17c7504a2e231bd8f4054b630f75 Mon Sep 17 00:00:00 2001
From: Kirithika <kirithika at multicorewareinc.com>
Date: Tue, 29 Jul 2025 10:28:50 +0530
Subject: [PATCH] SBRC: Tune ratefactor for simple/complex frames based on
 segment average

---
 source/encoder/ratecontrol.cpp | 12 ++++++------
 source/encoder/ratecontrol.h   |  4 ++--
 2 files changed, 8 insertions(+), 8 deletions(-)

diff --git a/source/encoder/ratecontrol.cpp b/source/encoder/ratecontrol.cpp
index 3de97c278..2e264e5ff 100644
--- a/source/encoder/ratecontrol.cpp
+++ b/source/encoder/ratecontrol.cpp
@@ -2038,7 +2038,7 @@ double RateControl::rateEstimateQscale(Frame* curFrame, RateControlEntry *rce)

         if (m_param->bEnableSBRC)
         {
-            qScale = tuneQscaleForSBRC(curFrame, qScale, rce);
+            qScale = tuneQscaleForSBRC(curFrame, qScale);
             rce->qpNoVbv = x265_qScale2qp(qScale);
         }

@@ -2264,8 +2264,10 @@ double RateControl::rateEstimateQscale(Frame* curFrame, RateControlEntry *rce)
                 if (m_param->bEnableSBRC)
                 {
                     double rfConstant = m_param->rc.rfConstant;
-                    if (m_currentSatd < m_movingSumComplexitySeg[rce->sliceType])
+                    if (m_currentSatd < (0.7 *m_movingSumComplexitySeg[rce->sliceType]))
                         rfConstant += 2;
+                    else if (m_currentSatd > (1.3 *m_movingSumComplexitySeg[rce->sliceType]))
+                        rfConstant -= 1;
                     double ipOffset = (curFrame->m_lowres.bScenecut ? m_ipOffset : m_ipOffset / 2.0);
                     rfConstant = (rce->sliceType == I_SLICE ? rfConstant - ipOffset :
                         (rce->sliceType == B_SLICE ? rfConstant + m_pbOffset : rfConstant));
@@ -2364,7 +2366,7 @@ double RateControl::rateEstimateQscale(Frame* curFrame, RateControlEntry *rce)
                 m_lastQScaleFor[P_SLICE] = X265_MAX(minScenecutQscale, m_lastQScaleFor[P_SLICE]);
             }
             if (m_param->bEnableSBRC)
-                q = tuneQscaleForSBRC(curFrame, q, rce);
+                q = tuneQscaleForSBRC(curFrame, q);

             rce->qpNoVbv = x265_qScale2qp(q);
             if (m_sliceType == P_SLICE)
@@ -2546,7 +2548,7 @@ double RateControl::predictSize(Predictor *p, double q, double var)
     return (p->coeff * var + p->offset) / (q * p->count);
 }

-double RateControl::tuneQscaleForSBRC(Frame* curFrame, double q, RateControlEntry* rce)
+double RateControl::tuneQscaleForSBRC(Frame* curFrame, double q)
 {
     int depth = 0;
     int framesDoneInSeg = m_framesDone % m_param->keyframeMax;
@@ -2579,8 +2581,6 @@ double RateControl::tuneQscaleForSBRC(Frame* curFrame, double q, RateControlEntr
         double allowedSize = m_vbvMaxRate * segDur;
         double remDur = segDur - totalDuration;
         double remainingBits = frameBitsTotal;
-
-        int framesLeft = m_param->totalFrames - m_framesDone;
         int isLastSegmentInaEncode = m_totalframesInSegment < m_param->keyframeMax;
         remainingBits = lookaheadBits / lookaheadDur * remDur;

diff --git a/source/encoder/ratecontrol.h b/source/encoder/ratecontrol.h
index 244511e45..2e3672d58 100644
--- a/source/encoder/ratecontrol.h
+++ b/source/encoder/ratecontrol.h
@@ -178,7 +178,7 @@ public:
     int     m_qpConstant[3];
     int     m_lastNonBPictType;
     int     m_framesDone;        /* # of frames passed through RateCotrol already */
-    int     m_iBits;
+    int64_t m_iBits;
     double  m_cplxrSum;          /* sum of bits*qscale/rceq */
     double  m_wantedBitsWindow;  /* target bitrate * window */
     double  m_accumPQp;          /* for determining I-frame quant */
@@ -305,7 +305,7 @@ protected:
     double rateEstimateQscale(Frame* pic, RateControlEntry *rce); // main logic for calculating QP based on ABR
     double tuneAbrQScaleFromFeedback(double qScale);
     double tuneQScaleForZone(RateControlEntry *rce, double qScale); // Tune qScale to adhere to zone budget
-    double tuneQscaleForSBRC(Frame* curFrame, double q, RateControlEntry *rce); // Tune qScale to adhere to segment budget
+    double tuneQscaleForSBRC(Frame* curFrame, double q); // Tune qScale to adhere to segment budget  
     void   accumPQpUpdate();

     int    getPredictorType(int lowresSliceType, int sliceType);
--
2.51.0.windows.1


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