Merge commit 'be00ec832c519427cd92218abac77dafdc1d5487'

[ffmpeg] / libavcodec / mpegaudio_tablegen.h

diff --git a/libavcodec/mpegaudio_tablegen.h b/libavcodec/mpegaudio_tablegen.h
index dd67a0977e2edd85bc315f908e54c464eb261bf3..0b0ea40682dc87d5e29d59bfd9b7f79033d9aef9 100644 (file)
--- a/libavcodec/mpegaudio_tablegen.h
+++ b/libavcodec/mpegaudio_tablegen.h
@@ -45,23 +45,28 @@ static float expval_table_float[512][16];
 static av_cold void mpegaudio_tableinit(void)
 {
     int i, value, exponent;
-    double exp2_lut[4] = {
+    static const double exp2_lut[4] = {
         1.00000000000000000000, /* 2 ^ (0 * 0.25) */
         1.18920711500272106672, /* 2 ^ (1 * 0.25) */
         M_SQRT2               , /* 2 ^ (2 * 0.25) */
         1.68179283050742908606, /* 2 ^ (3 * 0.25) */
     };
-    double cbrt_lut[16];
+    static double pow43_lut[16];
+    double exp2_base = 2.11758236813575084767080625169910490512847900390625e-22; // 2^(-72)
+    double exp2_val;
+    double pow43_val = 0;
     for (i = 0; i < 16; ++i)
-        cbrt_lut[i] = cbrt(i);
+        pow43_lut[i] = i * cbrt(i);
 
     for (i = 1; i < TABLE_4_3_SIZE; i++) {
-        double value = i / 4;
         double f, fm;
         int e, m;
-        f  = value / IMDCT_SCALAR * cbrt(value) * exp2_lut[i & 3];
+        double value = i / 4;
+        if ((i & 3) == 0)
+            pow43_val = value / IMDCT_SCALAR * cbrt(value);
+        f  = pow43_val * exp2_lut[i & 3];
         fm = frexp(f, &e);
-        m  = (uint32_t)(fm * (1LL << 31) + 0.5);
+        m  = llrint(fm * (1LL << 31));
         e += FRAC_BITS - 31 + 5 - 100;
 
         /* normalized to FRAC_BITS */
@@ -69,8 +74,11 @@ static av_cold void mpegaudio_tableinit(void)
         table_4_3_exp[i]   = -e;
     }
     for (exponent = 0; exponent < 512; exponent++) {
+        if (exponent && (exponent & 3) == 0)
+            exp2_base *= 2;
+        exp2_val = exp2_base * exp2_lut[exponent & 3] / IMDCT_SCALAR;
         for (value = 0; value < 16; value++) {
-            double f = value * cbrt_lut[value] * pow(2, (exponent - 400) * 0.25 + FRAC_BITS + 5) / IMDCT_SCALAR;
+            double f = pow43_lut[value] * exp2_val;
             expval_table_fixed[exponent][value] = (f < 0xFFFFFFFF ? llrint(f) : 0xFFFFFFFF);
             expval_table_float[exponent][value] = f;
         }