ref: 382ab797cfdb405b0a634629e926cee8590c99c2
parent: 273906404c1647ef9f43c27fc1efced3c7af96f4
author: Jean-Marc Valin <jmvalin@jmvalin.ca>
date: Thu Jul 21 15:48:55 EDT 2016
saturate MDCT output
--- a/celt/arch.h
+++ b/celt/arch.h
@@ -101,6 +101,9 @@
#define Q15ONE 32767
#define SIG_SHIFT 12
+/* Safe saturation value for 32-bit signals. Should be less than
+ 2^31*(1-0.85) to avoid blowing up on DC at deemphasis.*/
+#define SIG_SAT (300000000)
#define NORM_SCALING 16384
--- a/celt/mdct.c
+++ b/celt/mdct.c
@@ -306,8 +306,8 @@
/* We swap real and imag because we're using an FFT instead of an IFFT. */
re = yp1[1];
im = yp1[0];
- yp0[0] = yr;
- yp1[1] = yi;
+ yp0[0] = SATURATE(yr, SIG_SAT);
+ yp1[1] = SATURATE(yi, SIG_SAT);
t0 = t[(N4-i-1)];
t1 = t[(N2-i-1)];
@@ -314,8 +314,8 @@
/* We'd scale up by 2 here, but instead it's done when mixing the windows */
yr = ADD32_ovflw(S_MUL(re,t0), S_MUL(im,t1));
yi = SUB32_ovflw(S_MUL(re,t1), S_MUL(im,t0));
- yp1[0] = yr;
- yp0[1] = yi;
+ yp1[0] = SATURATE(yr, SIG_SAT);
+ yp0[1] = SATURATE(yi, SIG_SAT);
yp0 += 2;
yp1 -= 2;
}