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Update celt_log2_db fixed point to match new celt_log2 floating point.

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Change-Id: Ibd0d16918272cb568923d384475e139dc312c61b
Signed-off-by: Jean-Marc Valin <jeanmarcv@google.com>
This commit is contained in:
Yunho Huh 2024-12-09 08:25:38 +00:00 • committed by Jean-Marc Valin
parent e75503be94
commit 7fa23b4ed0
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GPG key ID: 8D2952BBB52C646D
2 changed files with 74 additions and 1 deletions
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43
celt/mathops.h
View file

@ -325,8 +325,49 @@ static OPUS_INLINE opus_val32 celt_exp2(opus_val16 x)
#ifdef ENABLE_QEXT
/* Calculates the base-2 logarithm of a Q14 input value. The result is returned
* in Q(DB_SHIFT). If the input value is 0, the function will output -32.0f. */
static OPUS_INLINE opus_val32 celt_log2_db(opus_val32 x) {
return (int)floor(.5 + (1<<DB_SHIFT) * 1.4426950409f*log(x/(float)(1<<14)));
/* Q30 */
static const opus_val32 log2_x_norm_coeff[8] = {
1073741824, 954437184, 858993472, 780903168,
715827904, 660764224, 613566784, 572662336};
/* Q24 */
static const opus_val32 log2_y_norm_coeff[8] = {
0, 2850868, 5401057, 7707983,
9814042, 11751428, 13545168, 15215099};
static const opus_val32 LOG2_COEFF_A0 = 1467383; /* Q24 */
static const opus_val32 LOG2_COEFF_A1 = 182244800; /* Q27 */
static const opus_val32 LOG2_COEFF_A2 = -21440512; /* Q25 */
static const opus_val32 LOG2_COEFF_A3 = 107903336; /* Q28 */
static const opus_val32 LOG2_COEFF_A4 = -610217024; /* Q31 */
opus_int32 integer, norm_coeff_idx, tmp;
opus_val32 mantissa;
if (x==0) {
return -536870912; /* -32.0f */
}
integer = SUB32(celt_ilog2(x), 14); /* Q0 */
mantissa = VSHR32(x, integer + 14 - 29); /* Q29 */
norm_coeff_idx = SHR32(mantissa, 29 - 3) & 0x7;
/* mantissa is in Q28 (29 + Q_NORM_CONST - 31 where Q_NORM_CONST is Q30)
* 285212672 (Q28) is 1.0625f. */
mantissa = SUB32(MULT32_32_Q31(mantissa, log2_x_norm_coeff[norm_coeff_idx]),
285212672);
/* q_a3(Q28): q_mantissa + q_a4 - 31
* q_a2(Q25): q_mantissa + q_a3 - 31
* q_a1(Q27): q_mantissa + q_a2 - 31 + 5
* q_a0(Q24): q_mantissa + q_a1 - 31
* where q_mantissa is Q28 */
/* Split evaluation in steps to avoid exploding macro expansion. */
tmp = MULT32_32_Q31(mantissa, LOG2_COEFF_A4);
tmp = MULT32_32_Q31(mantissa, ADD32(LOG2_COEFF_A3, tmp));
tmp = SHL32(MULT32_32_Q31(mantissa, ADD32(LOG2_COEFF_A2, tmp)), 5 /* SHL32 for LOG2_COEFF_A1 */);
tmp = MULT32_32_Q31(mantissa, ADD32(LOG2_COEFF_A1, tmp));
return ADD32(log2_y_norm_coeff[norm_coeff_idx],
ADD32(SHL32(integer, DB_SHIFT),
ADD32(LOG2_COEFF_A0, tmp)));
}
static OPUS_INLINE opus_val32 celt_exp2_db_frac(opus_val32 x)

32
celt/tests/test_unit_mathops.c
View file

@ -41,6 +41,8 @@
#ifdef FIXED_POINT
#define WORD "%d"
#define FIX_INT_TO_DOUBLE(x,q) ((double)(x) / (double)(1L << q))
#define DOUBLE_TO_FIX_INT(x,q) (((double)x * (double)(1L << q)))
#else
#define WORD "%f"
#endif
@ -204,6 +206,35 @@ void testexp2log2(void)
fprintf (stdout, "celt_exp2, celt_log2 max_error: %15.25e\n", max_error);
}
#else
void testlog2_db(void)
{
#if defined(ENABLE_QEXT)
/* celt_log2_db test */
float error = -1;
float max_error = -2;
float error_threshold = 2.e-07;
opus_int32 x = 0;
int q_input = 14;
for (x = 8; x < 1073741824; x += (x >> 3))
{
error = fabs((1.442695040888963387*log(FIX_INT_TO_DOUBLE(x, q_input))) -
FIX_INT_TO_DOUBLE(celt_log2_db(x), DB_SHIFT));
if (error > max_error)
{
max_error = error;
}
if (error > error_threshold)
{
fprintf(stderr, "celt_log2_db failed: error: [%.5e > %.5e] (x = %f)\n",
error, error_threshold, FIX_INT_TO_DOUBLE(x, DB_SHIFT));
ret = 1;
}
}
fprintf(stdout, "celt_log2_db max_error: %.7e\n", max_error);
#endif /* defined(ENABLE_QEXT) */
}
void testlog2(void)
{
opus_val32 x;
@ -283,6 +314,7 @@ int main(void)
testexp2log2();
#ifdef FIXED_POINT
testilog2();
testlog2_db();
#endif
return ret;
}