From 1e41f6702633f14e631ab9a42786a48515ba79ad Mon Sep 17 00:00:00 2001
From: "Christian R. Helmrich" <c.helmrich@ecodis.de>
Date: Thu, 11 Jun 2020 00:00:07 +0200
Subject: [PATCH] more rate reduction

---
 src/lib/exhaleEnc.cpp      |  3 ++-
 src/lib/specGapFilling.cpp | 29 +++++++++++++++++++++++++++--
 2 files changed, 29 insertions(+), 3 deletions(-)

diff --git a/src/lib/exhaleEnc.cpp b/src/lib/exhaleEnc.cpp
index 639342f..a347ebb 100644
--- a/src/lib/exhaleEnc.cpp
+++ b/src/lib/exhaleEnc.cpp
@@ -759,7 +759,8 @@ unsigned ExhaleEncoder::psychBitAllocation () // perceptual bit-allocation via s
   const unsigned lfeChannelIndex = (m_channelConf >= CCI_6_CH ? __max (5, nChannels - 1) : USAC_MAX_NUM_CHANNELS);
   const uint32_t maxSfbLong      = (samplingRate < 37566 ? 51 /*32 kHz*/ : brModeAndFsToMaxSfbLong (m_bitRateMode, samplingRate));
   const uint64_t scaleSr         = (samplingRate < 27713 ? (samplingRate < 24000 ? 32 : 34) - m_bitRateMode : 37) - (nChannels >> 1);
-  const uint64_t scaleBr         = (m_bitRateMode == 0 ? 4 + (samplingRate >> 10) : scaleSr - eightTimesSqrt256Minus[256 - m_bitRateMode] - __min (3, (m_bitRateMode - 1) >> 1));
+  const uint64_t scaleBr         = (m_bitRateMode == 0 ? __min (38, 3 + (samplingRate >> 10) + (samplingRate >> 13)) - (nChannels >> 1)
+                                   : scaleSr - eightTimesSqrt256Minus[256 - m_bitRateMode] - __min (3, (m_bitRateMode - 1) >> 1));
   uint32_t* sfbStepSizes = (uint32_t*) m_tempIntBuf;
   uint8_t  meanSpecFlat[USAC_MAX_NUM_CHANNELS];
 //uint8_t  meanTempFlat[USAC_MAX_NUM_CHANNELS];
diff --git a/src/lib/specGapFilling.cpp b/src/lib/specGapFilling.cpp
index 384afbd..51a0b26 100644
--- a/src/lib/specGapFilling.cpp
+++ b/src/lib/specGapFilling.cpp
@@ -21,6 +21,16 @@ SpecGapFiller::SpecGapFiller ()
   memset (m_1stNonZeroSfb, 0, sizeof (m_1stNonZeroSfb));
 }
 
+#if SGF_SF_PEAK_SMOOTHING
+static const unsigned smallDeltaHuffBitCount[15] = {8, 7, 6, 6, 5, 4, 3, 1, 4, 4, 5, 6, 6, 7, 7};
+
+static inline unsigned huffBitCountEstimate (const int scaleFactorDelta)
+{
+  if (abs (scaleFactorDelta) < 8) return smallDeltaHuffBitCount[scaleFactorDelta + 7];
+  return (abs (scaleFactorDelta) >> 1) + 4;
+}
+#endif
+
 // public functions
 uint8_t SpecGapFiller::getSpecGapFillParams (const SfbQuantizer& sfbQuantizer, const uint8_t* const quantMagn,
                                              const uint8_t numSwbShort, SfbGroupData& grpData /*modified*/,
@@ -239,16 +249,31 @@ uint8_t SpecGapFiller::getSpecGapFillParams (const SfbQuantizer& sfbQuantizer, c
 
       for (x = start + 1; x < sfbsPerGrp; x++)
       {
-        const int32_t xZ = size * (x - start) - xSum; // zero-mean
+        const int32_t xZ  = size * (x - start) - xSum; // zero-mean
+
         a += xZ * xZ;
         b += xZ * (size * grpScFacs[x] - ySum);
       }
       if (a > 0) // complete line and adjust gap-fill scale factors
       {
+        unsigned countOld = 0, countNew = 0;
+
         b = CLIP_PM (((b << 8) + (a >> 1)) / a, SHRT_MAX);
         a = ((ySum << 8) - b * xSum + (size >> 1)) / size;
 
-        for (x = start + 1; x < sfbsPerGrp; x++) grpScFacs[x] = CLIP_UCHAR ((a + b * (x - start) - SCHAR_MIN) >> 8);
+        ySum = grpScFacs[start];
+        for (x = start + 1; x < sfbsPerGrp; x++)
+        {
+          const int32_t y = CLIP_UCHAR ((a + b * (x - start) - SCHAR_MIN) >> 8);
+
+          countOld += huffBitCountEstimate ((int) grpScFacs[x] - grpScFacs[x - 1]);
+          countNew += huffBitCountEstimate (y - ySum);
+          ySum = y;
+        }
+        if (countNew < countOld)
+        {
+          for (x = start + 1; x < sfbsPerGrp; x++) grpScFacs[x] = CLIP_UCHAR ((a + b * (x - start) - SCHAR_MIN) >> 8);
+        }
       }
     }
 #endif