/******************************************************************************
*
* Copyright 2022 Google LLC
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at:
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*
******************************************************************************/
#include "spec.h"
#include "bits.h"
#include "tables.h"
/* ----------------------------------------------------------------------------
* Global Gain / Quantization
* -------------------------------------------------------------------------- */
/**
* Resolve quantized gain index offset
* sr, nbytes Samplerate and size of the frame
* return Gain index offset
*/
static int resolve_gain_offset(enum lc3_srate sr, int nbytes)
{
int sr_ind = lc3_hr(sr) ? 4 + (sr - LC3_SRATE_48K_HR) : sr;
int g_off = (nbytes * 8) / (10 * (1 + sr_ind));
return LC3_MIN(sr >= LC3_SRATE_96K_HR ? 181 : 255,
105 + 5*(1 + sr_ind) + LC3_MIN(g_off, 115));
}
/**
* Unquantize gain
* g_int Quantization gain value
* return Unquantized gain value
*/
static float unquantize_gain(int g_int)
{
/* Unquantization gain table :
* G[i] = 10 ^ (i / 28) , i = [0..27] */
static const float iq_table[] = {
1.00000000e+00, 1.08571112e+00, 1.17876863e+00, 1.27980221e+00,
1.38949549e+00, 1.50859071e+00, 1.63789371e+00, 1.77827941e+00,
1.93069773e+00, 2.09617999e+00, 2.27584593e+00, 2.47091123e+00,
2.68269580e+00, 2.91263265e+00, 3.16227766e+00, 3.43332002e+00,
3.72759372e+00, 4.04708995e+00, 4.39397056e+00, 4.77058270e+00,
5.17947468e+00, 5.62341325e+00, 6.10540230e+00, 6.62870316e+00,
7.19685673e+00, 7.81370738e+00, 8.48342898e+00, 9.21055318e+00
};
float g = 1.f;
for ( ; g_int < 0; g_int += 28, g *= 0.1f);
for ( ; g_int >= 28; g_int -= 28, g *= 10.f);
return g * iq_table[g_int];
}
/**
* Global Gain Estimation
* dt, sr Duration and samplerate of the frame
* x Spectral coefficients
* nbytes Size of the frame
* nbits_budget Number of bits available coding the spectrum
* nbits_off Offset on the available bits, temporarily smoothed
* g_off Gain index offset
* reset_off Return True when the nbits_off must be reset
* g_min Return lower bound of quantized gain value
* return The quantized gain value
*/
LC3_HOT static int estimate_gain(
enum lc3_dt dt, enum lc3_srate sr, const float *x,
int nbytes, int nbits_budget, float nbits_off, int g_off,
bool *reset_off, int *g_min)
{
int n4 = lc3_ne(dt, sr) / 4;
union { float f; int32_t q16; } e[LC3_MAX_NE / 4];
/* --- Signal adaptative noise floor --- */
int reg_bits = 0;
float low_bits = 0;
if (lc3_hr(sr)) {
int reg_c = (const int [LC3_NUM_DT][LC3_NUM_SRATE - LC3_SRATE_48K_HR]){
[LC3_DT_2M5] = { -6, -6 },
[LC3_DT_5M ] = { 0, 0 },
[LC3_DT_10M] = { 2, 5 }
}[dt][sr - LC3_SRATE_48K_HR];
reg_bits = (8*nbytes * 4) / (125 * (1 + dt));
reg_bits = LC3_CLIP(reg_bits + reg_c, 6, 23);
float m0 = 1e-5f, m1 = 1e-5f, k = 0;
for (int i = 0; i < n4; i++) {
m0 += fabsf(x[4*i + 0]), m1 += fabsf(x[4*i + 0]) * k++;
m0 += fabsf(x[4*i + 1]), m1 += fabsf(x[4*i + 1]) * k++;
m0 += fabsf(x[4*i + 2]), m1 += fabsf(x[4*i + 2]) * k++;
m0 += fabsf(x[4*i + 3]), m1 += fabsf(x[4*i + 3]) * k++;
}
int m = roundf((1.6f * m0) / ((1 + dt) * m1));
low_bits = 8 - LC3_MIN(m, 8);
}
/* --- Energy (dB) by 4 MDCT blocks --- */
float x2_max = 0;
for (int i = 0; i < n4; i++) {
float x0 = x[4*i + 0] * x[4*i + 0];
float x1 = x[4*i + 1] * x[4*i + 1];
float x2 = x[4*i + 2] * x[4*i + 2];
float x3 = x[4*i + 3] * x[4*i + 3];
x2_max = fmaxf(x2_max, x0);
x2_max = fmaxf(x2_max, x1);
x2_max = fmaxf(x2_max, x2);
x2_max = fmaxf(x2_max, x3);
e[i].f = x0 + x1 + x2 + x3;
}
float x_max = sqrtf(x2_max);
float nf = lc3_hr(sr) ?
lc3_ldexpf(x_max, -reg_bits) * lc3_exp2f(-low_bits) : 0;
for (int i = 0; i < n4; i++)
e[i].q16 = lc3_db_q16(fmaxf(e[i].f + nf, 1e-10f));
/* --- Determine gain index --- */
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 = n4-1, j1 ; i > 0; i >>= 1) {
int gn = (g_int - i) * k_20_28;
int v = 0;
for (j = j0; j >= 0 && e[j].q16 < gn; j--);
for (j1 = j; j >= 0; j--) {
int e_diff = e[j].q16 - gn;
v += e_diff < 0 ? k_2u7 :
e_diff < 43 << 16 ? e_diff + ( 7 << 16)
: 2*e_diff - (36 << 16);
}
if (v > nbits * k_1u4)
j0 = j1;
else
g_int = g_int - i;
}
/* --- Limit gain index --- */
float x_lim = lc3_hr(sr) ? 0x7fffp8f : 0x7fffp0f;
*g_min = 255 - g_off;
for (int i = 128 ; i > 0; i >>= 1)
if (x_lim * unquantize_gain(*g_min - i) > x_max)
*g_min -= i;
*reset_off = g_int < *g_min || x_max == 0;
if (*reset_off)
g_int = *g_min;
return g_int;
}
/**
* Global Gain Adjustment
* dt, sr Duration and samplerate of the frame
* g_idx The estimated quantized gain index
* nbits Computed number of bits coding the spectrum
* nbits_budget Number of bits available for coding the spectrum
* g_idx_min Minimum gain index value
* return Gain adjust value (-1 to 2)
*/
LC3_HOT static int adjust_gain(
enum lc3_dt dt, enum lc3_srate sr,
int g_idx, int nbits, int nbits_budget, int g_idx_min)
{
/* --- Compute delta threshold --- */
const int *t = (const int [LC3_NUM_SRATE][3]){
{ 80, 500, 850 }, { 230, 1025, 1700 }, { 380, 1550, 2550 },
{ 530, 2075, 3400 }, { 680, 2600, 4250 },
{ 680, 2600, 4250 }, { 830, 3125, 5100 }
}[sr];
int delta, den = 48;
if (nbits < t[0]) {
delta = 3*(nbits + 48);
} else if (nbits < t[1]) {
int n0 = 3*(t[0] + 48), range = t[1] - t[0];
delta = n0 * range + (nbits - t[0]) * (t[1] - n0);
den *= range;
} else {
delta = LC3_MIN(nbits, t[2]);
}
delta = (delta + den/2) / den;
/* --- Adjust gain --- */
if (lc3_hr(sr) && nbits > nbits_budget) {
int factor = 1 + (dt <= LC3_DT_5M) +
(dt <= LC3_DT_2M5) * (1 + (nbits >= 520));
int g_incr = factor + (factor * (nbits - nbits_budget)) / delta;
return LC3_MIN(g_idx + g_incr, 255) - g_idx;
}
if (!lc3_hr(sr) && nbits < nbits_budget - (delta + 2))
return -(g_idx > g_idx_min);
if (!lc3_hr(sr) && nbits > nbits_budget)
return (g_idx < 255) + (g_idx < 254 && nbits >= nbits_budget + delta);
return 0;
}
/**
* Spectrum quantization
* dt, sr Duration and samplerate of the frame
* g_int Quantization gain value
* x Spectral coefficients, scaled as output
* n Return count of significants
*/
LC3_HOT static void quantize(
enum lc3_dt dt, enum lc3_srate sr, int g_int, float *x, int *n)
{
float g_inv = unquantize_gain(-g_int);
int ne = lc3_ne(dt, sr);
*n = ne;
for (int i = 0; i < ne; i += 2) {
float xq_min = lc3_hr(sr) ? 0.5f : 10.f/16;
x[i+0] *= g_inv;
x[i+1] *= g_inv;
*n = fabsf(x[i+0]) >= xq_min ||
fabsf(x[i+1]) >= xq_min ? ne : *n - 2;
}
}
/**
* Spectrum quantization inverse
* dt, sr Duration and samplerate of the frame
* g_int Quantization gain value
* x, nq Spectral quantized, and count of significants
* return Unquantized gain value
*/
LC3_HOT static float unquantize(
enum lc3_dt dt, enum lc3_srate sr,
int g_int, float *x, int nq)
{
float g = unquantize_gain(g_int);
int i, ne = lc3_ne(dt, sr);
for (i = 0; i < nq; i++)
x[i] = x[i] * g;
for ( ; i < ne; i++)
x[i] = 0;
return g;
}
/* ----------------------------------------------------------------------------
* Spectrum coding
* -------------------------------------------------------------------------- */
/**
* Resolve High-bitrate and LSB modes according size of the frame
* sr, nbytes Samplerate and size of the frame
* p_lsb_mode True when LSB mode allowed, when not NULL
* return True when High-Rate mode enabled
*/
static bool resolve_modes(enum lc3_srate sr, int nbytes, bool *p_lsb_mode)
{
int sr_ind = lc3_hr(sr) ? 4 + (sr - LC3_SRATE_48K_HR) : sr;
if (p_lsb_mode)
*p_lsb_mode = (nbytes >= 20 * (3 + sr_ind)) && (sr < LC3_SRATE_96K_HR);
return (nbytes > 20 * (1 + sr_ind)) && (sr < LC3_SRATE_96K_HR);
}
/**
* Bit consumption
* dt, sr, nbytes Duration, samplerate and size of the frame
* x Spectral quantized coefficients
* n Count of significant coefficients, updated on truncation
* nbits_budget Truncate to stay in budget, when not zero
* p_lsb_mode Return True when LSB's are not AC coded, or NULL
* return The number of bits coding the spectrum
*/
LC3_HOT static int compute_nbits(
enum lc3_dt dt, enum lc3_srate sr, int nbytes,
const float *x, int *n, int nbits_budget, bool *p_lsb_mode)
{
bool lsb_mode, high_rate = resolve_modes(sr, nbytes, &lsb_mode);
int ne = lc3_ne(dt, sr);
/* --- Loop on quantized coefficients --- */
int nbits = 0, nbits_lsb = 0;
uint8_t state = 0;
int nbits_end = 0;
int n_end = 0;
nbits_budget = nbits_budget ? nbits_budget * 2048 : INT_MAX;
for (int i = 0, h = 0; h < 2; h++) {
const uint8_t (*lut_coeff)[4] = lc3_spectrum_lookup[high_rate][h];
for ( ; i < LC3_MIN(*n, (ne + 2) >> (1 - h))
&& nbits <= nbits_budget; i += 2) {
float xq_off = lc3_hr(sr) ? 0.5f : 6.f/16;
uint32_t a = fabsf(x[i+0]) + xq_off;
uint32_t b = fabsf(x[i+1]) + xq_off;
const uint8_t *lut = lut_coeff[state];
/* --- Sign values --- */
int s = (a != 0) + (b != 0);
nbits += s * 2048;
/* --- LSB values Reduce to 2*2 bits MSB values ---
* Reduce to 2x2 bits MSB values. The LSB's pair are arithmetic
* coded with an escape code followed by 1 bit for each values.
* The LSB mode does not arthmetic code the first LSB,
* add the sign of the LSB when one of pair was at value 1 */
uint32_t m = (a | b) >> 2;
unsigned k = 0;
if (m) {
if (lsb_mode) {
nbits += lc3_spectrum_bits[lut[k++]][16] - 2*2048;
nbits_lsb += 2 + (a == 1) + (b == 1);
}
for (m >>= lsb_mode; m; m >>= 1, k++)
nbits += lc3_spectrum_bits[lut[LC3_MIN(k, 3)]][16];
nbits += k * 2*2048;
a >>= k;
b >>= k;
k = LC3_MIN(k, 3);
}
/* --- MSB values --- */
nbits += lc3_spectrum_bits[lut[k]][a + 4*b];
/* --- Update state --- */
if (s && nbits <= nbits_budget) {
n_end = i + 2;
nbits_end = nbits;
}
state = (state << 4) + (k > 1 ? 12 + k : 1 + (a + b) * (k + 1));
}
}
/* --- Return --- */
*n = n_end;
if (p_lsb_mode)
*p_lsb_mode = lsb_mode &&
nbits_end + nbits_lsb * 2048 > nbits_budget;
if (nbits_budget >= INT_MAX)
nbits_end += nbits_lsb * 2048;
return (nbits_end + 2047) / 2048;
}
/**
* Put quantized spectrum
* bits Bitstream context
* dt, sr, nbytes Duration, samplerate and size of the frame
* x Spectral quantized coefficients
* nq, lsb_mode Count of significants, and LSB discard indication
*/
LC3_HOT static void put_quantized(lc3_bits_t *bits,
enum lc3_dt dt, enum lc3_srate sr, int nbytes,
const float *x, int nq, bool lsb_mode)
{
bool high_rate = resolve_modes(sr, nbytes, NULL);
int ne = lc3_ne(dt, sr);
/* --- Loop on quantized coefficients --- */
uint8_t state = 0;
for (int i = 0, h = 0; h < 2; h++) {
const uint8_t (*lut_coeff)[4] = lc3_spectrum_lookup[high_rate][h];
for ( ; i < LC3_MIN(nq, (ne + 2) >> (1 - h)); i += 2) {
float xq_off = lc3_hr(sr) ? 0.5f : 6.f/16;
uint32_t a = fabsf(x[i+0]) + xq_off;
uint32_t b = fabsf(x[i+1]) + xq_off;
const uint8_t *lut = lut_coeff[state];
/* --- LSB values Reduce to 2*2 bits MSB values ---
* Reduce to 2x2 bits MSB values. The LSB's pair are arithmetic
* coded with an escape code and 1 bits for each values.
* The LSB mode discard the first LSB (at this step) */
uint32_t m = (a | b) >> 2;
unsigned k = 0, shr = 0;
if (m) {
if (lsb_mode)
lc3_put_symbol(bits,
lc3_spectrum_models + lut[k++], 16);
for (m >>= lsb_mode; m; m >>= 1, k++) {
lc3_put_bit(bits, (a >> k) & 1);
lc3_put_bit(bits, (b >> k) & 1);
lc3_put_symbol(bits,
lc3_spectrum_models + lut[LC3_MIN(k, 3)], 16);
}
a >>= lsb_mode;
b >>= lsb_mode;
shr = k - lsb_mode;
k = LC3_MIN(k, 3);
}
/* --- Sign values --- */
if (a) lc3_put_bit(bits, x[i+0] < 0);
if (b) lc3_put_bit(bits, x[i+1] < 0);
/* --- MSB values --- */
a >>= shr;
b >>= shr;
lc3_put_symbol(bits, lc3_spectrum_models + lut[k], a + 4*b);
/* --- Update state --- */
state = (state << 4) + (k > 1 ? 12 + k : 1 + (a + b) * (k + 1));
}
}
}
/**
* Get quantized spectrum
* bits Bitstream context
* dt, sr, nbytes Duration, samplerate and size of the frame
* nq, lsb_mode Count of significants, and LSB discard indication
* x Return `nq` spectral quantized coefficients
* nf_seed Return the noise factor seed associated
* return 0: Ok -1: Invalid bitstream data
*/
LC3_HOT static int get_quantized(lc3_bits_t *bits,
enum lc3_dt dt, enum lc3_srate sr, int nbytes,
int nq, bool lsb_mode, float *x, uint16_t *nf_seed)
{
bool high_rate = resolve_modes(sr, nbytes, NULL);
int ne = lc3_ne(dt, sr);
*nf_seed = 0;
/* --- Loop on quantized coefficients --- */
uint8_t state = 0;
for (int i = 0, h = 0; h < 2; h++) {
const uint8_t (*lut_coeff)[4] = lc3_spectrum_lookup[high_rate][h];
for ( ; i < LC3_MIN(nq, (ne + 2) >> (1 - h)); i += 2) {
const uint8_t *lut = lut_coeff[state];
int max_shl = lc3_hr(sr) ? 22 : 14;
/* --- LSB values ---
* Until the symbol read indicates the escape value 16,
* read an LSB bit for each values.
* The LSB mode discard the first LSB (at this step) */
int u = 0, v = 0;
int k = 0, shl = 0;
unsigned s = lc3_get_symbol(bits, lc3_spectrum_models + lut[k]);
if (lsb_mode && s >= 16) {
s = lc3_get_symbol(bits, lc3_spectrum_models + lut[++k]);
shl++;
}
for ( ; s >= 16 && shl < max_shl; shl++) {
u |= lc3_get_bit(bits) << shl;
v |= lc3_get_bit(bits) << shl;
k += (k < 3);
s = lc3_get_symbol(bits, lc3_spectrum_models + lut[k]);
}
if (s >= 16)
return -1;
/* --- MSB & sign values --- */
int a = s % 4;
int b = s / 4;
u |= a << shl;
v |= b << shl;
x[i+0] = u && lc3_get_bit(bits) ? -u : u;
x[i+1] = v && lc3_get_bit(bits) ? -v : v;
*nf_seed = (*nf_seed + (u & 0x7fff) * (i )
+ (v & 0x7fff) * (i+1)) & 0xffff;
/* --- Update state --- */
state = (state << 4) + (k > 1 ? 12 + k : 1 + (a + b) * (k + 1));
}
}
return 0;
}
/**
* Put residual bits of quantization
* bits Bitstream context
* nbits Maximum number of bits to output
* hrmode High-Resolution mode
* x, n Spectral quantized, and count of significants
*/
LC3_HOT static void put_residual(lc3_bits_t *bits,
int nbits, bool hrmode, float *x, int n)
{
float xq_lim = hrmode ? 0.5f : 10.f/16;
float xq_off = xq_lim / 2;
for (int iter = 0; iter < (hrmode ? 20 : 1) && nbits > 0; iter++) {
for (int i = 0; i < n && nbits > 0; i++) {
float xr = fabsf(x[i]);
if (xr < xq_lim)
continue;
bool b = (xr - truncf(xr) < xq_lim) ^ (x[i] < 0);
lc3_put_bit(bits, b);
nbits--;
x[i] += b ? -xq_off : xq_off;
}
xq_off *= xq_lim;
}
}
/**
* Get residual bits of quantization
* bits Bitstream context
* nbits Maximum number of bits to output
* hrmode High-Resolution mode
* x, nq Spectral quantized, and count of significants
*/
LC3_HOT static void get_residual(lc3_bits_t *bits,
int nbits, bool hrmode, float *x, int n)
{
float xq_off_1 = hrmode ? 0.25f : 5.f/16;
float xq_off_2 = hrmode ? 0.25f : 3.f/16;
for (int iter = 0; iter < (hrmode ? 20 : 1) && nbits > 0; iter++) {
for (int i = 0; i < n && nbits > 0; i++) {
if (x[i] == 0)
continue;
if (lc3_get_bit(bits) == 0)
x[i] -= x[i] < 0 ? xq_off_1 : xq_off_2;
else
x[i] += x[i] > 0 ? xq_off_1 : xq_off_2;
nbits--;
}
xq_off_1 *= 0.5f;
xq_off_2 *= 0.5f;
}
}
/**
* Put LSB values of quantized spectrum values
* bits Bitstream context
* nbits Maximum number of bits to output
* hrmode High-Resolution mode
* x, n Spectral quantized, and count of significants
*/
LC3_HOT static void put_lsb(lc3_bits_t *bits,
int nbits, bool hrmode, const float *x, int n)
{
for (int i = 0; i < n && nbits > 0; i += 2) {
float xq_off = hrmode ? 0.5f : 6.f/16;
uint32_t a = fabsf(x[i+0]) + xq_off;
uint32_t b = fabsf(x[i+1]) + xq_off;
if ((a | b) >> 2 == 0)
continue;
if (nbits-- > 0)
lc3_put_bit(bits, a & 1);
if (a == 1 && nbits-- > 0)
lc3_put_bit(bits, x[i+0] < 0);
if (nbits-- > 0)
lc3_put_bit(bits, b & 1);
if (b == 1 && nbits-- > 0)
lc3_put_bit(bits, x[i+1] < 0);
}
}
/**
* Get LSB values of quantized spectrum values
* bits Bitstream context
* nbits Maximum number of bits to output
* x, nq Spectral quantized, and count of significants
* nf_seed Update the noise factor seed according
*/
LC3_HOT static void get_lsb(lc3_bits_t *bits,
int nbits, float *x, int nq, uint16_t *nf_seed)
{
for (int i = 0; i < nq && nbits > 0; i += 2) {
float a = fabsf(x[i]), b = fabsf(x[i+1]);
if (fmaxf(a, b) < 4)
continue;
if (nbits-- > 0 && lc3_get_bit(bits)) {
if (a) {
x[i] += x[i] < 0 ? -1 : 1;
*nf_seed = (*nf_seed + i) & 0xffff;
} else if (nbits-- > 0) {
x[i] = lc3_get_bit(bits) ? -1 : 1;
*nf_seed = (*nf_seed + i) & 0xffff;
}
}
if (nbits-- > 0 && lc3_get_bit(bits)) {
if (b) {
x[i+1] += x[i+1] < 0 ? -1 : 1;
*nf_seed = (*nf_seed + i+1) & 0xffff;
} else if (nbits-- > 0) {
x[i+1] = lc3_get_bit(bits) ? -1 : 1;
*nf_seed = (*nf_seed + i+1) & 0xffff;
}
}
}
}
/* ----------------------------------------------------------------------------
* Noise coding
* -------------------------------------------------------------------------- */
/**
* Estimate noise level
* dt, bw Duration and bandwidth of the frame
* hrmode High-Resolution mode
* x, n Spectral quantized, and count of significants
* return Noise factor (0 to 7)
*/
LC3_HOT static int estimate_noise(
enum lc3_dt dt, enum lc3_bandwidth bw, bool hrmode, const float *x, int n)
{
int bw_stop = lc3_ne(dt, (enum lc3_srate)LC3_MIN(bw, LC3_BANDWIDTH_FB));
int w = 1 + (dt >= LC3_DT_7M5) + (dt>= LC3_DT_10M);
float xq_lim = hrmode ? 0.5f : 10.f/16;
float sum = 0;
int i, ns = 0, z = 0;
for (i = 6 * (1 + dt) - w; i < LC3_MIN(n, bw_stop); i++) {
z = fabsf(x[i]) < xq_lim ? z + 1 : 0;
if (z > 2*w)
sum += fabsf(x[i - w]), ns++;
}
for ( ; i < bw_stop + w; i++)
if (++z > 2*w)
sum += fabsf(x[i - w]), ns++;
int nf = ns ? 8 - (int)((16 * sum) / ns + 0.5f) : 8;
return LC3_CLIP(nf, 0, 7);
}
/**
* Noise filling
* dt, bw Duration and bandwidth of the frame
* nf, nf_seed The noise factor and pseudo-random seed
* g Quantization gain
* x, nq Spectral quantized, and count of significants
*/
LC3_HOT static void fill_noise(enum lc3_dt dt, enum lc3_bandwidth bw,
int nf, uint16_t nf_seed, float g, float *x, int nq)
{
int bw_stop = lc3_ne(dt, (enum lc3_srate)LC3_MIN(bw, LC3_BANDWIDTH_FB));
int w = 1 + (dt >= LC3_DT_7M5) + (dt>= LC3_DT_10M);
float s = g * (float)(8 - nf) / 16;
int i, z = 0;
for (i = 6 * (1 + dt) - w; i < LC3_MIN(nq, bw_stop); i++) {
z = x[i] ? 0 : z + 1;
if (z > 2*w) {
nf_seed = (13849 + nf_seed*31821) & 0xffff;
x[i - w] = nf_seed & 0x8000 ? -s : s;
}
}
for ( ; i < bw_stop + w; i++)
if (++z > 2*w) {
nf_seed = (13849 + nf_seed*31821) & 0xffff;
x[i - w] = nf_seed & 0x8000 ? -s : s;
}
}
/**
* Put noise factor
* bits Bitstream context
* nf Noise factor (0 to 7)
*/
static void put_noise_factor(lc3_bits_t *bits, int nf)
{
lc3_put_bits(bits, nf, 3);
}
/**
* Get noise factor
* bits Bitstream context
* return Noise factor (0 to 7)
*/
static int get_noise_factor(lc3_bits_t *bits)
{
return lc3_get_bits(bits, 3);
}
/* ----------------------------------------------------------------------------
* Encoding
* -------------------------------------------------------------------------- */
/**
* Bit consumption of the number of coded coefficients
* dt, sr, nbytes Duration, samplerate and size of the frame
* return Bit consumpution of the number of coded coefficients
*/
static int get_nbits_nq(enum lc3_dt dt, enum lc3_srate sr)
{
int ne = lc3_ne(dt, sr);
return 4 + (ne > 32) + (ne > 64) + (ne > 128) + (ne > 256) + (ne > 512);
}
/**
* Bit consumption of the arithmetic coder
* dt, sr, nbytes Duration, samplerate and size of the frame
* return Bit consumption of bitstream data
*/
static int get_nbits_ac(enum lc3_dt dt, enum lc3_srate sr, int nbytes)
{
return get_nbits_nq(dt, sr) +
3 + lc3_hr(sr) + LC3_MIN((nbytes-1) / 160, 2);
}
/**
* Spectrum analysis
*/
void lc3_spec_analyze(
enum lc3_dt dt, enum lc3_srate sr, int nbytes,
bool pitch, const lc3_tns_data_t *tns,
struct lc3_spec_analysis *spec,
float *x, struct lc3_spec_side *side)
{
bool reset_off;
/* --- Bit budget --- */
const int nbits_gain = 8;
const int nbits_nf = 3;
int nbits_budget = 8*nbytes - get_nbits_ac(dt, sr, nbytes) -
lc3_bwdet_get_nbits(sr) - lc3_ltpf_get_nbits(pitch) -
lc3_sns_get_nbits() - lc3_tns_get_nbits(tns) - nbits_gain - nbits_nf;
/* --- Global gain --- */
float nbits_off = spec->nbits_off + spec->nbits_spare;
nbits_off = fminf(fmaxf(nbits_off, -40), 40);
nbits_off = 0.8f * spec->nbits_off + 0.2f * nbits_off;
int g_off = resolve_gain_offset(sr, nbytes);
int g_min, g_int = estimate_gain(dt, sr,
x, nbytes, nbits_budget, nbits_off, g_off, &reset_off, &g_min);
/* --- Quantization --- */
quantize(dt, sr, g_int, x, &side->nq);
int nbits = compute_nbits(dt, sr, nbytes, x, &side->nq, 0, NULL);
spec->nbits_off = reset_off ? 0 : nbits_off;
spec->nbits_spare = reset_off ? 0 : nbits_budget - nbits;
/* --- Adjust gain and requantize --- */
int g_adj = adjust_gain(dt, sr,
g_off + g_int, nbits, nbits_budget, g_off + g_min);
if (g_adj)
quantize(dt, sr, g_adj, x, &side->nq);
side->g_idx = g_int + g_adj + g_off;
nbits = compute_nbits(dt, sr, nbytes,
x, &side->nq, nbits_budget, &side->lsb_mode);
}
/**
* Put spectral quantization side data
*/
void lc3_spec_put_side(lc3_bits_t *bits,
enum lc3_dt dt, enum lc3_srate sr,
const struct lc3_spec_side *side)
{
int nbits_nq = get_nbits_nq(dt, sr);
lc3_put_bits(bits, LC3_MAX(side->nq >> 1, 1) - 1, nbits_nq);
lc3_put_bits(bits, side->lsb_mode, 1);
lc3_put_bits(bits, side->g_idx, 8);
}
/**
* Encode spectral coefficients
*/
void lc3_spec_encode(lc3_bits_t *bits,
enum lc3_dt dt, enum lc3_srate sr, enum lc3_bandwidth bw,
int nbytes, const lc3_spec_side_t *side, float *x)
{
bool lsb_mode = side->lsb_mode;
int nq = side->nq;
put_noise_factor(bits, estimate_noise(dt, bw, lc3_hr(sr), x, nq));
put_quantized(bits, dt, sr, nbytes, x, nq, lsb_mode);
int nbits_left = lc3_get_bits_left(bits);
if (lsb_mode)
put_lsb(bits, nbits_left, lc3_hr(sr), x, nq);
else
put_residual(bits, nbits_left, lc3_hr(sr), x, nq);
}
/* ----------------------------------------------------------------------------
* Decoding
* -------------------------------------------------------------------------- */
/**
* Get spectral quantization side data
*/
int lc3_spec_get_side(lc3_bits_t *bits,
enum lc3_dt dt, enum lc3_srate sr, struct lc3_spec_side *side)
{
int nbits_nq = get_nbits_nq(dt, sr);
int ne = lc3_ne(dt, sr);
side->nq = (lc3_get_bits(bits, nbits_nq) + 1) << 1;
side->lsb_mode = lc3_get_bit(bits);
side->g_idx = lc3_get_bits(bits, 8);
return side->nq > ne ? (side->nq = ne), -1 : 0;
}
/**
* Decode spectral coefficients
*/
int lc3_spec_decode(lc3_bits_t *bits,
enum lc3_dt dt, enum lc3_srate sr, enum lc3_bandwidth bw,
int nbytes, const lc3_spec_side_t *side, float *x)
{
bool lsb_mode = side->lsb_mode;
int nq = side->nq;
int ret = 0;
int nf = get_noise_factor(bits);
uint16_t nf_seed;
if ((ret = get_quantized(bits, dt, sr, nbytes,
nq, lsb_mode, x, &nf_seed)) < 0)
return ret;
int nbits_left = lc3_get_bits_left(bits);
if (lsb_mode)
get_lsb(bits, nbits_left, x, nq, &nf_seed);
else
get_residual(bits, nbits_left, lc3_hr(sr), x, nq);
int g_int = side->g_idx - resolve_gain_offset(sr, nbytes);
float g = unquantize(dt, sr, g_int, x, nq);
if (nq > 2 || x[0] || x[1] || side->g_idx > 0 || nf < 7)
fill_noise(dt, bw, nf, nf_seed, g, x, nq);
return 0;
}