avcodec/aac_tablegen: get rid of hardcoded tables entirely

Commit 96786a12f6df26990bbe7c0ca4592b3731724469 makes runtime
initialization cheap.

Tested with FATE, with/without --enable-hardcoded-tables.

Reviewed-by: Rostislav Pehlivanov <atomnuker@gmail.com>
Signed-off-by: Ganesh Ajjanagadde <gajjanagadde@gmail.com>

1 files changed, 49 insertions, 1 deletions

diff --git a/libavcodec/aactab.h b/libavcodec/aactab.h
index 321c5d392a..b48e7da6ed 100644
--- a/libavcodec/aactab.h
+++ b/libavcodec/aactab.h
@@ -32,7 +32,6 @@
 
 #include "libavutil/mem.h"
 #include "aac.h"
-#include "aac_tablegen_decl.h"
 
 #include <stdint.h>
 
@@ -40,6 +39,55 @@
  * Tables in this file are shared by the AAC decoders and encoder
  */
 
+extern float ff_aac_pow2sf_tab[428];
+extern float ff_aac_pow34sf_tab[428];
+
+static inline void ff_aac_tableinit(void)
+{
+    int i;
+
+    /* 2^(i/16) for 0 <= i <= 15 */
+    static const float exp2_lut[] = {
+        1.00000000000000000000,
+        1.04427378242741384032,
+        1.09050773266525765921,
+        1.13878863475669165370,
+        1.18920711500272106672,
+        1.24185781207348404859,
+        1.29683955465100966593,
+        1.35425554693689272830,
+        1.41421356237309504880,
+        1.47682614593949931139,
+        1.54221082540794082361,
+        1.61049033194925430818,
+        1.68179283050742908606,
+        1.75625216037329948311,
+        1.83400808640934246349,
+        1.91520656139714729387,
+    };
+    float t1 = 8.8817841970012523233890533447265625e-16; // 2^(-50)
+    float t2 = 3.63797880709171295166015625e-12; // 2^(-38)
+    int t1_inc_cur, t2_inc_cur;
+    int t1_inc_prev = 0;
+    int t2_inc_prev = 8;
+
+    for (i = 0; i < 428; i++) {
+        t1_inc_cur = 4 * (i % 4);
+        t2_inc_cur = (8 + 3*i) % 16;
+        if (t1_inc_cur < t1_inc_prev)
+            t1 *= 2;
+        if (t2_inc_cur < t2_inc_prev)
+            t2 *= 2;
+        // A much more efficient and accurate way of doing:
+        // ff_aac_pow2sf_tab[i] = pow(2, (i - POW_SF2_ZERO) / 4.0);
+        // ff_aac_pow34sf_tab[i] = pow(ff_aac_pow2sf_tab[i], 3.0/4.0);
+        ff_aac_pow2sf_tab[i] = t1 * exp2_lut[t1_inc_cur];
+        ff_aac_pow34sf_tab[i] = t2 * exp2_lut[t2_inc_cur];
+        t1_inc_prev = t1_inc_cur;
+        t2_inc_prev = t2_inc_cur;
+    }
+}
+
 /* @name ltp_coef
  * Table of the LTP coefficients
  */