Slight update to the UHJ coefficients

The extended precision of the encoder's 0.6512*X term was guesswork, with no
real basis for it. Switch back to the original value until something better
actually comes up. Also updates the decoder to account for the change in the
encoder.

3 files changed, 46 insertions, 46 deletions

diff --git a/core/uhjfilter.cpp b/core/uhjfilter.cpp
index 0875211c..282ed2b3 100644
--- a/core/uhjfilter.cpp
+++ b/core/uhjfilter.cpp
@@ -28,7 +28,7 @@ const PhaseShifterT<UhjFilterBase::sFilterDelay*2> PShift{};
  *
  * Left = (S + D)/2.0
  * Right = (S - D)/2.0
- * T = j(-0.1432*W + 0.6511746*X) - 0.7071068*Y
+ * T = j(-0.1432*W + 0.6512*X) - 0.7071068*Y
  * Q = 0.9772*Z
  *
  * where j is a wide-band +90 degree phase shift. 3-channel UHJ excludes Q,
@@ -95,9 +95,9 @@ void UhjEncoder::encode(float *LeftOut, float *RightOut, const FloatBufferLine *
  * S = Left + Right
  * D = Left - Right
  *
- * W = 0.981530*S + 0.197484*j(0.828347*D + 0.767835*T)
- * X = 0.418504*S - j(0.828347*D + 0.767835*T)
- * Y = 0.795954*D - 0.676406*T + j(0.186626*S)
+ * W = 0.981532*S + 0.197484*j(0.828331*D + 0.767820*T)
+ * X = 0.418496*S - j(0.828331*D + 0.767820*T)
+ * Y = 0.795968*D - 0.676392*T + j(0.186633*S)
  * Z = 1.023332*Q
  *
  * where j is a +90 degree phase shift. 3-channel UHJ excludes Q, while 2-
@@ -130,19 +130,19 @@ void UhjDecoder::decode(const al::span<BufferLine> samples, const size_t offset,
     float *RESTRICT xoutput{samples[1].data() + offset};
     float *RESTRICT youtput{samples[2].data() + offset};
 
-    /* Precompute j(0.828347*D + 0.767835*T) and store in xoutput. */
+    /* Precompute j(0.828331*D + 0.767820*T) and store in xoutput. */
     auto tmpiter = std::copy(mDTHistory.cbegin(), mDTHistory.cend(), mTemp.begin());
     std::transform(mD.cbegin(), mD.cbegin()+samplesToDo+sFilterDelay, mT.cbegin(), tmpiter,
-        [](const float d, const float t) noexcept { return 0.828347f*d + 0.767835f*t; });
+        [](const float d, const float t) noexcept { return 0.828331f*d + 0.767820f*t; });
     std::copy_n(mTemp.cbegin()+forwardSamples, mDTHistory.size(), mDTHistory.begin());
     PShift.process({xoutput, samplesToDo}, mTemp.data());
 
-    /* W = 0.981530*S + 0.197484*j(0.828347*D + 0.767835*T) */
+    /* W = 0.981532*S + 0.197484*j(0.828331*D + 0.767820*T) */
     for(size_t i{0};i < samplesToDo;++i)
-        woutput[i] = 0.981530f*mS[i] + 0.197484f*xoutput[i];
-    /* X = 0.418504*S - j(0.828347*D + 0.767835*T) */
+        woutput[i] = 0.981532f*mS[i] + 0.197484f*xoutput[i];
+    /* X = 0.418496*S - j(0.828331*D + 0.767820*T) */
     for(size_t i{0};i < samplesToDo;++i)
-        xoutput[i] = 0.418504f*mS[i] - xoutput[i];
+        xoutput[i] = 0.418496f*mS[i] - xoutput[i];
 
     /* Precompute j*S and store in youtput. */
     tmpiter = std::copy(mSHistory.cbegin(), mSHistory.cend(), mTemp.begin());
@@ -150,9 +150,9 @@ void UhjDecoder::decode(const al::span<BufferLine> samples, const size_t offset,
     std::copy_n(mTemp.cbegin()+forwardSamples, mSHistory.size(), mSHistory.begin());
     PShift.process({youtput, samplesToDo}, mTemp.data());
 
-    /* Y = 0.795954*D - 0.676406*T + j(0.186626*S) */
+    /* Y = 0.795968*D - 0.676392*T + j(0.186633*S) */
     for(size_t i{0};i < samplesToDo;++i)
-        youtput[i] = 0.795954f*mD[i] - 0.676406f*mT[i] + 0.186626f*youtput[i];
+        youtput[i] = 0.795968f*mD[i] - 0.676392f*mT[i] + 0.186633f*youtput[i];
 
     if(samples.size() > 3)
     {
diff --git a/utils/uhjdecoder.cpp b/utils/uhjdecoder.cpp
index 4c45afd7..7bb1a51a 100644
--- a/utils/uhjdecoder.cpp
+++ b/utils/uhjdecoder.cpp
@@ -141,9 +141,9 @@ const PhaseShifterT<UhjDecoder::sFilterDelay*2> PShift{};
  * S = Left + Right
  * D = Left - Right
  *
- * W = 0.981530*S + 0.197484*j(0.828347*D + 0.767835*T)
- * X = 0.418504*S - j(0.828347*D + 0.767835*T)
- * Y = 0.795954*D - 0.676406*T + j(0.186626*S)
+ * W = 0.981532*S + 0.197484*j(0.828331*D + 0.767820*T)
+ * X = 0.418496*S - j(0.828331*D + 0.767820*T)
+ * Y = 0.795968*D - 0.676392*T + j(0.186633*S)
  * Z = 1.023332*Q
  *
  * where j is a +90 degree phase shift. 3-channel UHJ excludes Q, while 2-
@@ -162,49 +162,49 @@ const PhaseShifterT<UhjDecoder::sFilterDelay*2> PShift{};
  * Gerzon's original paper for deriving Sigma (S) or Delta (D) from the L and R
  * signals. As proof, taking Y for example:
  *
- * Y = 0.795954*D - 0.676406*T + j(0.186626*S)
+ * Y = 0.795968*D - 0.676392*T + j(0.186633*S)
  *
  * * Plug in the encoding parameters, using ? as a placeholder for whether S
  *   and D should receive an extra 0.5 factor
- * Y = 0.795954*(j(-0.3420201*W + 0.5098604*X) + 0.6554516*Y)*? -
- *     0.676406*(j(-0.1432*W + 0.6511746*X) - 0.7071068*Y) +
- *     0.186626*j(0.9396926*W + 0.1855740*X)*?
+ * Y = 0.795968*(j(-0.3420201*W + 0.5098604*X) + 0.6554516*Y)*? -
+ *     0.676392*(j(-0.1432*W + 0.6512*X) - 0.7071068*Y) +
+ *     0.186633*j(0.9396926*W + 0.1855740*X)*?
  *
  * * Move common factors in
- * Y = (j(-0.3420201*0.795954*?*W + 0.5098604*0.795954*?*X) + 0.6554516*0.795954*?*Y) -
- *     (j(-0.1432*0.676406*W + 0.6511746*0.676406*X) - 0.7071068*0.676406*Y) +
- *     j(0.9396926*0.186626*?*W + 0.1855740*0.186626*?*X)
+ * Y = (j(-0.3420201*0.795968*?*W + 0.5098604*0.795968*?*X) + 0.6554516*0.795968*?*Y) -
+ *     (j(-0.1432*0.676392*W + 0.6512*0.676392*X) - 0.7071068*0.676392*Y) +
+ *     j(0.9396926*0.186633*?*W + 0.1855740*0.186633*?*X)
  *
  * * Clean up extraneous groupings
- * Y = j(-0.3420201*0.795954*?*W + 0.5098604*0.795954*?*X) + 0.6554516*0.795954*?*Y -
- *     j(-0.1432*0.676406*W + 0.6511746*0.676406*X) + 0.7071068*0.676406*Y +
- *     j*(0.9396926*0.186626*?*W + 0.1855740*0.186626*?*X)
+ * Y = j(-0.3420201*0.795968*?*W + 0.5098604*0.795968*?*X) + 0.6554516*0.795968*?*Y -
+ *     j(-0.1432*0.676392*W + 0.6512*0.676392*X) + 0.7071068*0.676392*Y +
+ *     j*(0.9396926*0.186633*?*W + 0.1855740*0.186633*?*X)
  *
  * * Move phase shifts together and combine them
- * Y = j(-0.3420201*0.795954*?*W + 0.5098604*0.795954*?*X - -0.1432*0.676406*W -
- *        0.6511746*0.676406*X + 0.9396926*0.186626*?*W + 0.1855740*0.186626*?*X) +
- *     0.6554516*0.795954*?*Y + 0.7071068*0.676406*Y
+ * Y = j(-0.3420201*0.795968*?*W + 0.5098604*0.795968*?*X - -0.1432*0.676392*W -
+ *        0.6512*0.676392*X + 0.9396926*0.186633*?*W + 0.1855740*0.186633*?*X) +
+ *     0.6554516*0.795968*?*Y + 0.7071068*0.676392*Y
  *
  * * Reorder terms
- * Y = j(-0.3420201*0.795954*?*W +  0.1432*0.676406*W + 0.9396926*0.186626*?*W +
- *        0.5098604*0.795954*?*X + -0.6511746*0.676406*X + 0.1855740*0.186626*?*X) +
- *     0.7071068*0.676406*Y + 0.6554516*0.795954*?*Y
+ * Y = j(-0.3420201*0.795968*?*W +  0.1432*0.676392*W + 0.9396926*0.186633*?*W +
+ *        0.5098604*0.795968*?*X + -0.6512*0.676392*X + 0.1855740*0.186633*?*X) +
+ *     0.7071068*0.676392*Y + 0.6554516*0.795968*?*Y
  *
  * * Move common factors out
- * Y = j((-0.3420201*0.795954*? +  0.1432*0.676406 + 0.9396926*0.186626*?)*W +
- *       ( 0.5098604*0.795954*? + -0.6511746*0.676406 + 0.1855740*0.186626*?)*X) +
- *     (0.7071068*0.676406 + 0.6554516*0.795954*?)*Y
+ * Y = j((-0.3420201*0.795968*? +  0.1432*0.676392 + 0.9396926*0.186633*?)*W +
+ *       ( 0.5098604*0.795968*? + -0.6512*0.676392 + 0.1855740*0.186633*?)*X) +
+ *     (0.7071068*0.676392 + 0.6554516*0.795968*?)*Y
  *
  * * Result w/ 0.5 factor:
- * -0.3420201*0.795954*0.5 + 0.1432*0.676406 + 0.9396926*0.186626*0.5 = 0.04843*W
- * 0.5098604*0.795954*0.5 + -0.6511746*0.676406 + 0.1855740*0.186626*0.5 = -0.22023*X
- * 0.7071068*0.676406 + 0.6554516*0.795954*0.5 = 0.73915*Y
- * -> Y = j(0.04843*W + -0.22023*X) + 0.73915*Y
+ * -0.3420201*0.795968*0.5 +  0.1432*0.676392 + 0.9396926*0.186633*0.5 =  0.04843*W
+ *  0.5098604*0.795968*0.5 + -0.6512*0.676392 + 0.1855740*0.186633*0.5 = -0.22023*X
+ *  0.7071068*0.676392                        + 0.6554516*0.795968*0.5 =  0.73914*Y
+ * -> Y = j(0.04843*W + -0.22023*X) + 0.73914*Y
  *
  * * Result w/o 0.5 factor:
- * -0.3420201*0.795954 + 0.1432*0.676406 + 0.9396926*0.186626 = 0.00000*W
- * 0.5098604*0.795954 + -0.6511746*0.676406 + 0.1855740*0.186626 = 0.00000*X
- * 0.7071068*0.676406 + 0.6554516*0.795954 = 1.00000*Y
+ * -0.3420201*0.795968 +  0.1432*0.676392 + 0.9396926*0.186633 = 0.00000*W
+ *  0.5098604*0.795968 + -0.6512*0.676392 + 0.1855740*0.186633 = 0.00000*X
+ *  0.7071068*0.676392                    + 0.6554516*0.795968 = 1.00000*Y
  * -> Y = j(0.00000*W + 0.00000*X) + 1.00000*Y
  *
  * Not halving produces a result matching the original input.
@@ -252,8 +252,8 @@ void UhjDecoder::decode(const float *RESTRICT InSamples, const size_t InChannels
 
     for(size_t i{0};i < SamplesToDo;++i)
     {
-        /* W = 0.981530*S + 0.197484*j(0.828347*D + 0.767835*T) */
-        woutput[i] = 0.981530f*mS[i] + 0.197484f*xoutput[i];
+        /* W = 0.981532*S + 0.197484*j(0.828347*D + 0.767835*T) */
+        woutput[i] = 0.981532f*mS[i] + 0.197484f*xoutput[i];
         /* X = 0.418504*S - j(0.828347*D + 0.767835*T) */
         xoutput[i] = 0.418504f*mS[i] - xoutput[i];
     }
@@ -266,8 +266,8 @@ void UhjDecoder::decode(const float *RESTRICT InSamples, const size_t InChannels
 
     for(size_t i{0};i < SamplesToDo;++i)
     {
-        /* Y = 0.795954*D - 0.676406*T + j(0.186626*S) */
-        youtput[i] = 0.795954f*mD[i] - 0.676406f*mT[i] + 0.186626f*youtput[i];
+        /* Y = 0.795968*D - 0.676392*T + j(0.186633*S) */
+        youtput[i] = 0.795968f*mD[i] - 0.676392f*mT[i] + 0.186633f*youtput[i];
     }
 
     if(OutSamples.size() > 3)
diff --git a/utils/uhjencoder.cpp b/utils/uhjencoder.cpp
index 73e21479..700d1b17 100644
--- a/utils/uhjencoder.cpp
+++ b/utils/uhjencoder.cpp
@@ -89,7 +89,7 @@ const PhaseShifterT<UhjEncoder::sFilterDelay*2> PShift{};
  *
  * Left = (S + D)/2.0
  * Right = (S - D)/2.0
- * T = j(-0.1432*W + 0.6511746*X) - 0.7071068*Y
+ * T = j(-0.1432*W + 0.6512*X) - 0.7071068*Y
  * Q = 0.9772*Z
  *
  * where j is a wide-band +90 degree phase shift. T is excluded from 2-channel