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spec: Move gain estimation in fixed point

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This commit is contained in:
Antoine SOULIER
2022-05-12 10:17:20 +02:00
parent 15240c5f9e
commit bba71917f2
3 changed files with 104 additions and 23 deletions
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49
src/spec.c
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@@ -51,25 +51,24 @@ LC3_HOT static int estimate_gain(
int nbits_budget, float nbits_off, int g_off, bool *reset_off)
{
int ne = LC3_NE(dt, sr) >> 2;
float e[ne];
int e[ne];
/* --- Energy (dB) by 4 NDCT blocks ---
* For the next steps, add energy offset 28/20 dB,
* and compute the maximum magnitude */
/* --- Energy (dB) by 4 MDCT blocks --- */
float x_max = 0;
float x2_max = 0;
for (int i = 0; i < ne; i++, x += 4) {
float x0 = fabsf(x[0]), x1 = fabsf(x[1]);
float x2 = fabsf(x[2]), x3 = fabsf(x[3]);
float x0 = x[0] * x[0];
float x1 = x[1] * x[1];
float x2 = x[2] * x[2];
float x3 = x[3] * x[3];
x_max = fmaxf(x_max, x0);
x_max = fmaxf(x_max, x1);
x_max = fmaxf(x_max, x2);
x_max = fmaxf(x_max, x3);
x2_max = fmaxf(x2_max, x0);
x2_max = fmaxf(x2_max, x1);
x2_max = fmaxf(x2_max, x2);
x2_max = fmaxf(x2_max, x3);
float s2 = x0*x0 + x1*x1 + x2*x2 + x3*x3;
e[i] = 28.f/20 * 10 * (s2 > 0 ? fast_log10f(s2) : -10);
e[i] = fast_db_q16(fmaxf(x0 + x1 + x2 + x3, 1e-10f));
}
/* --- Determine gain index --- */
@@ -77,21 +76,25 @@ LC3_HOT static int estimate_gain(
int nbits = nbits_budget + nbits_off + 0.5f;
int g_int = 255 - g_off;
const int k_20_28 = 20.f/28 * 0x1p16f + 0.5f;
const int k_2u7 = 2.7f * 0x1p16f + 0.5f;
const int k_1u4 = 1.4f * 0x1p16f + 0.5f;
for (int i = 128, j, j0 = ne-1, j1 ; i > 0; i >>= 1) {
float gn = g_int - i;
float v = 0;
int gn = (g_int - i) * k_20_28;
int v = 0;
for (j = j0; j >= 0 && e[j] < gn; j--);
for (j1 = j; j >= 0; j--) {
float e_diff = e[j] - gn;
int e_diff = e[j] - gn;
v += e_diff < 0 ? 2.7f * 28.f/20 :
e_diff < 43 * 28.f/20 ? e_diff + 7 * 28.f/20 :
2*e_diff - 36 * 28.f/20 ;
v += e_diff < 0 ? k_2u7 :
e_diff < 43 << 16 ? e_diff + ( 7 << 16)
: 2*e_diff - (36 << 16);
}
if (v > nbits * 1.4f * 28.f/20)
if (v > nbits * k_1u4)
j0 = j1;
else
g_int = g_int - i;
@@ -99,10 +102,10 @@ LC3_HOT static int estimate_gain(
/* --- Limit gain index --- */
int g_min = x_max == 0 ? -g_off :
ceilf(28 * log10f(x_max / (32768 - 0.375f)));
int g_min = x2_max == 0 ? -g_off :
ceilf(28 * log10f(sqrtf(x2_max) / (32768 - 0.375f)));
*reset_off = g_int < g_min || x_max == 0;
*reset_off = g_int < g_min || x2_max == 0;
if (*reset_off)
g_int = g_min;