diff options
| -rw-r--r-- | libavcodec/mpegaudio_tablegen.h | 22 |
1 files changed, 15 insertions, 7 deletions
diff --git a/libavcodec/mpegaudio_tablegen.h b/libavcodec/mpegaudio_tablegen.h index dd67a0977e..1b273146cc 100644 --- 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; } |