shithub: opus

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ref: e0f26246b08122cef31c1ac85f7ed228e2daca61
parent: 4a168eb343af95be4b3a00ef2c5cf40da1d6b7e0
author: Jean-Marc Valin <[email protected]>
date: Sat Dec 14 06:07:13 EST 2013 

fixed-point: adds rounding to some shifts to eliminate bias

This reduces the peak decoding error by removing small (inaudible) spikes in
the error at the frame boundaries. These were due to the frequency-domain bias
ending up as a small pulse in the middle of the IMDCT overlap. None of this
was ever audible, but fixing it is still cleaner.


--- a/celt/bands.c
+++ b/celt/bands.c
@@ -430,7 +430,7 @@
    {
       celt_norm r, l;
       /* Apply mid scaling (side is already scaled) */
-      l = MULT16_16_Q15(mid, X[j]);
+      l = MULT16_16_P15(mid, X[j]);
       r = Y[j];
       X[j] = EXTRACT16(PSHR32(MULT16_16(lgain, SUB16(l,r)), kl+1));
       Y[j] = EXTRACT16(PSHR32(MULT16_16(rgain, ADD16(l,r)), kr+1));
@@ -600,8 +600,8 @@
          opus_val32 tmp1, tmp2;
          tmp1 = MULT16_16(QCONST16(.70710678f,15), X[stride*2*j+i]);
          tmp2 = MULT16_16(QCONST16(.70710678f,15), X[stride*(2*j+1)+i]);
-         X[stride*2*j+i] = EXTRACT16(SHR32(ADD32(tmp1, tmp2), 15));
-         X[stride*(2*j+1)+i] = EXTRACT16(SHR32(SUB32(tmp1, tmp2), 15));
+         X[stride*2*j+i] = EXTRACT16(PSHR32(ADD32(tmp1, tmp2), 15));
+         X[stride*(2*j+1)+i] = EXTRACT16(PSHR32(SUB32(tmp1, tmp2), 15));
       }
 }
 
--- a/celt/vq.c
+++ b/celt/vq.c
@@ -49,8 +49,8 @@
       celt_norm x1, x2;
       x1 = Xptr[0];
       x2 = Xptr[stride];
-      Xptr[stride] = EXTRACT16(SHR32(MULT16_16(c,x2) + MULT16_16(s,x1), 15));
-      *Xptr++      = EXTRACT16(SHR32(MULT16_16(c,x1) - MULT16_16(s,x2), 15));
+      Xptr[stride] = EXTRACT16(PSHR32(MULT16_16(c,x2) + MULT16_16(s,x1), 15));
+      *Xptr++      = EXTRACT16(PSHR32(MULT16_16(c,x1) - MULT16_16(s,x2), 15));
    }
    Xptr = &X[len-2*stride-1];
    for (i=len-2*stride-1;i>=0;i--)
@@ -58,8 +58,8 @@
       celt_norm x1, x2;
       x1 = Xptr[0];
       x2 = Xptr[stride];
-      Xptr[stride] = EXTRACT16(SHR32(MULT16_16(c,x2) + MULT16_16(s,x1), 15));
-      *Xptr--      = EXTRACT16(SHR32(MULT16_16(c,x1) - MULT16_16(s,x2), 15));
+      Xptr[stride] = EXTRACT16(PSHR32(MULT16_16(c,x2) + MULT16_16(s,x1), 15));
+      *Xptr--      = EXTRACT16(PSHR32(MULT16_16(c,x1) - MULT16_16(s,x2), 15));
    }
 }