diff --git a/src/dsp/enc_sse2.c b/src/dsp/enc_sse2.c
index 6b21dc2d..6c8faf17 100644
--- a/src/dsp/enc_sse2.c
+++ b/src/dsp/enc_sse2.c
@@ -830,8 +830,6 @@ static int QuantizeBlockSSE2(int16_t in[16], int16_t out[16],
   const __m128i bias8 = _mm_loadu_si128((__m128i*)&mtx->bias_[8]);
   const __m128i q0 = _mm_loadu_si128((__m128i*)&mtx->q_[0]);
   const __m128i q8 = _mm_loadu_si128((__m128i*)&mtx->q_[8]);
-  const __m128i zthresh0 = _mm_loadu_si128((__m128i*)&mtx->zthresh_[0]);
-  const __m128i zthresh8 = _mm_loadu_si128((__m128i*)&mtx->zthresh_[8]);
 
   // sign(in) = in >> 15  (0x0000 if positive, 0xffff if negative)
   const __m128i sign0 = _mm_srai_epi16(in0, 15);
@@ -894,17 +892,8 @@ static int QuantizeBlockSSE2(int16_t in[16], int16_t out[16],
   in0 = _mm_mullo_epi16(out0, q0);
   in8 = _mm_mullo_epi16(out8, q8);
 
-  // if (coeff <= mtx->zthresh_) {in=0; out=0;}
-  {
-    __m128i cmp0 = _mm_cmpgt_epi16(coeff0, zthresh0);
-    __m128i cmp8 = _mm_cmpgt_epi16(coeff8, zthresh8);
-    in0 = _mm_and_si128(in0, cmp0);
-    in8 = _mm_and_si128(in8, cmp8);
-    _mm_storeu_si128((__m128i*)&in[0], in0);
-    _mm_storeu_si128((__m128i*)&in[8], in8);
-    out0 = _mm_and_si128(out0, cmp0);
-    out8 = _mm_and_si128(out8, cmp8);
-  }
+  _mm_storeu_si128((__m128i*)&in[0], in0);
+  _mm_storeu_si128((__m128i*)&in[8], in8);
 
   // zigzag the output before storing it.
   //
diff --git a/src/enc/quant.c b/src/enc/quant.c
index a287d61c..3f1ae8e7 100644
--- a/src/enc/quant.c
+++ b/src/enc/quant.c
@@ -169,19 +169,13 @@ static const uint16_t kAcTable2[128] = {
   385, 393, 401, 409, 416, 424, 432, 440
 };
 
-static const uint16_t kCoeffThresh[16] = {
-  0,  10, 20, 30,
-  10, 20, 30, 30,
-  20, 30, 30, 30,
-  30, 30, 30, 30
-};
-
 static const uint8_t kBiasMatrices[3][2] = {  // [luma-ac,luma-dc,chroma][dc,ac]
-  { 96, 110 }, { 96, 112 }, { 112, 120 }
+  { 96, 110 }, { 96, 108 }, { 110, 115 }
 };
 
 // Sharpening by (slightly) raising the hi-frequency coeffs.
 // Hack-ish but helpful for mid-bitrate range. Use with care.
+#define SHARPEN_BITS 11  // number of descaling bits for sharpening bias
 static const uint8_t kFreqSharpening[16] = {
   0,  30, 60, 90,
   30, 60, 90, 90,
@@ -204,9 +198,15 @@ static int ExpandMatrix(VP8Matrix* const m, int type) {
     const int bias = kBiasMatrices[type][is_ac_coeff];
     m->iq_[i] = (1 << QFIX) / m->q_[i];
     m->bias_[i] = BIAS(bias);
-    // TODO(skal): tune kCoeffThresh[]
-    m->zthresh_[i] = ((256 /*+ kCoeffThresh[i]*/ - bias) * m->q_[i] + 127) >> 8;
-    m->sharpen_[i] = (kFreqSharpening[i] * m->q_[i]) >> 11;
+    // zthresh_ is the exact value such that QUANTDIV(coeff, iQ, B) is:
+    //   * zero if coeff <= zthresh
+    //   * non-zero if coeff > zthresh
+    m->zthresh_[i] = ((1 << QFIX) - 1 - m->bias_[i]) / m->iq_[i];
+    if (type == 0) {  // we only use sharpening for AC luma coeffs
+      m->sharpen_[i] = (kFreqSharpening[i] * m->q_[i]) >> SHARPEN_BITS;
+    } else {
+      m->sharpen_[i] = 0;
+    }
     sum += m->q_[i];
   }
   return (sum + 8) >> 4;