[x265] [PATCH] Reduce QP for the scene changes that is followed by black frames

[pooja at multicorewareinc.com]

# HG changeset patch
# User Pooja Venkatesan <pooja at multicorewareinc.com>
# Date 1552816785 -19800
#      Sun Mar 17 15:29:45 2019 +0530
# Node ID f0b531ade27567f539d80e2592de146475f68080
# Parent  de920e0a31831f52599f3937c3ee6945e88ed851
Reduce QP for the scene changes that is followed by black frames

During a scenecut, the transition from black frames to a different sequence
gives a high QP value. Reducing tune complexity factor for the scene
change in ABR reduces QP.

diff -r de920e0a3183 -r f0b531ade275 source/encoder/ratecontrol.cpp
--- a/source/encoder/ratecontrol.cpp	Tue Jul 23 17:03:51 2019 +0530
+++ b/source/encoder/ratecontrol.cpp	Sun Mar 17 15:29:45 2019 +0530
@@ -2116,6 +2116,9 @@
             if ((underflow < epsilon || rce->isFadeEnd) && !isFrameDone)
             {
                 init(*m_curSlice->m_sps);
+                // Reduce tune complexity factor for scenes that follow blank frames
+                double tuneCplxFactor = (m_ncu > 3600 && m_param->rc.cuTree && !m_param->rc.hevcAq) ? 2.5 : m_param->rc.hevcAq ? 1.5 : m_isGrainEnabled ? 1.9 : 1.0;
+                m_cplxrSum /= tuneCplxFactor;
                 m_shortTermCplxSum = rce->lastSatd / (CLIP_DURATION(m_frameDuration) / BASE_FRAME_DURATION);
                 m_shortTermCplxCount = 1;
                 m_isAbrReset = true;
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