diff options
Diffstat (limited to 'codecs/ilbc/lsf.c')
-rwxr-xr-x | codecs/ilbc/lsf.c | 252 |
1 files changed, 252 insertions, 0 deletions
diff --git a/codecs/ilbc/lsf.c b/codecs/ilbc/lsf.c new file mode 100755 index 000000000..f768b7782 --- /dev/null +++ b/codecs/ilbc/lsf.c @@ -0,0 +1,252 @@ + +/****************************************************************** + + iLBC Speech Coder ANSI-C Source Code + + lsf.c + + Copyright (c) 2001, + Global IP Sound AB. + All rights reserved. + +******************************************************************/ + +#include <string.h> +#include <math.h> + +#include "iLBC_define.h" + +/*----------------------------------------------------------------* + * conversion from lpc coefficients to lsf coefficients + *---------------------------------------------------------------*/ + +void a2lsf( + float *freq,/* (o) lsf coefficients */ + float *a /* (i) lpc coefficients */ +){ + float steps[LSF_NUMBER_OF_STEPS] = + {(float)0.00635, (float)0.003175, (float)0.0015875, + (float)0.00079375}; + float step; + int step_idx; + int lsp_index; + float p[LPC_HALFORDER]; + float q[LPC_HALFORDER]; + float p_pre[LPC_HALFORDER]; + float q_pre[LPC_HALFORDER]; + float old_p, old_q, *old; + float *pq_coef; + float omega, old_omega; + int i; + float hlp, hlp1, hlp2, hlp3, hlp4, hlp5; + + for (i = 0; i < LPC_HALFORDER; i++){ + p[i] = (float)-1.0 * (a[i + 1] + a[LPC_FILTERORDER - i]); + q[i] = a[LPC_FILTERORDER - i] - a[i + 1]; + } + + p_pre[0] = (float)-1.0 - p[0]; + p_pre[1] = - p_pre[0] - p[1]; + p_pre[2] = - p_pre[1] - p[2]; + p_pre[3] = - p_pre[2] - p[3]; + p_pre[4] = - p_pre[3] - p[4]; + p_pre[4] = p_pre[4] / 2; + + q_pre[0] = (float)1.0 - q[0]; + q_pre[1] = q_pre[0] - q[1]; + q_pre[2] = q_pre[1] - q[2]; + q_pre[3] = q_pre[2] - q[3]; + q_pre[4] = q_pre[3] - q[4]; + q_pre[4] = q_pre[4] / 2; + + omega = 0.0; + old_omega = 0.0; + + old_p = FLOAT_MAX; + old_q = FLOAT_MAX; + + /* Here we loop through lsp_index to find all the + LPC_FILTERORDER roots for omega. */ + + for (lsp_index = 0; lsp_index < LPC_FILTERORDER; lsp_index++){ + + /* Depending on lsp_index being even or odd, we + alternatively solve the roots for the two LSP equations. */ + + + if ((lsp_index & 0x1) == 0) { + pq_coef = p_pre; + old = &old_p; + } else { + pq_coef = q_pre; + old = &old_q; + } + + /* Start with low resolution grid */ + + for (step_idx = 0, step = steps[step_idx]; + step_idx < LSF_NUMBER_OF_STEPS;){ + + /* cos(10piw) + pq(0)cos(8piw) + pq(1)cos(6piw) + + pq(2)cos(4piw) + pq(3)cod(2piw) + pq(4) */ + + hlp = (float)cos(omega * TWO_PI); + hlp1 = (float)2.0 * hlp + pq_coef[0]; + hlp2 = (float)2.0 * hlp * hlp1 - (float)1.0 + + pq_coef[1]; + hlp3 = (float)2.0 * hlp * hlp2 - hlp1 + pq_coef[2]; + hlp4 = (float)2.0 * hlp * hlp3 - hlp2 + pq_coef[3]; + hlp5 = hlp * hlp4 - hlp3 + pq_coef[4]; + + + if (((hlp5 * (*old)) <= 0.0) || (omega >= 0.5)){ + + if (step_idx == (LSF_NUMBER_OF_STEPS - 1)){ + + if (fabs(hlp5) >= fabs(*old)) { + freq[lsp_index] = omega - step; + } else { + freq[lsp_index] = omega; + } + + + if ((*old) >= 0.0){ + *old = (float)-1.0 * FLOAT_MAX; + } else { + *old = FLOAT_MAX; + } + + omega = old_omega; + step_idx = 0; + + step_idx = LSF_NUMBER_OF_STEPS; + } else { + + if (step_idx == 0) { + old_omega = omega; + } + + step_idx++; + omega -= steps[step_idx]; + + /* Go back one grid step */ + + step = steps[step_idx]; + } + } else { + + /* increment omega until they are of different sign, + and we know there is at least one root between omega + and old_omega */ + *old = hlp5; + omega += step; + } + } + } + + for (i = 0; i < LPC_FILTERORDER; i++) { + freq[i] = freq[i] * TWO_PI; + } +} + +/*----------------------------------------------------------------* + * conversion from lsf coefficients to lpc coefficients + *---------------------------------------------------------------*/ + +void lsf2a( + float *a_coef, /* (o) lpc coefficients */ + float *freq /* (i) lsf coefficients */ +){ + int i, j; + float hlp; + float p[LPC_HALFORDER], q[LPC_HALFORDER]; + float a[LPC_HALFORDER + 1], a1[LPC_HALFORDER], a2[LPC_HALFORDER]; + float b[LPC_HALFORDER + 1], b1[LPC_HALFORDER], b2[LPC_HALFORDER]; + + for (i = 0; i < LPC_FILTERORDER; i++) { + freq[i] = freq[i] * PI2; + } + + /* Check input for ill-conditioned cases. This part is not + found in the TIA standard. It involves the following 2 IF + blocks. If "freq" is judged ill-conditioned, then we first + modify freq[0] and freq[LPC_HALFORDER-1] (normally + LPC_HALFORDER = 10 for LPC applications), then we adjust + the other "freq" values slightly */ + + + if ((freq[0] <= 0.0) || (freq[LPC_FILTERORDER - 1] >= 0.5)){ + + + if (freq[0] <= 0.0) { + freq[0] = (float)0.022; + } + + + if (freq[LPC_FILTERORDER - 1] >= 0.5) { + freq[LPC_FILTERORDER - 1] = (float)0.499; + } + + hlp = (freq[LPC_FILTERORDER - 1] - freq[0]) / + (float) (LPC_FILTERORDER - 1); + + for (i = 1; i < LPC_FILTERORDER; i++) { + freq[i] = freq[i - 1] + hlp; + } + } + + memset(a1, 0, LPC_HALFORDER*sizeof(float)); + memset(a2, 0, LPC_HALFORDER*sizeof(float)); + memset(b1, 0, LPC_HALFORDER*sizeof(float)); + memset(b2, 0, LPC_HALFORDER*sizeof(float)); + memset(a, 0, (LPC_HALFORDER+1)*sizeof(float)); + memset(b, 0, (LPC_HALFORDER+1)*sizeof(float)); + + /* p[i] and q[i] compute cos(2*pi*omega_{2j}) and + cos(2*pi*omega_{2j-1} in eqs. 4.2.2.2-1 and 4.2.2.2-2. + Note that for this code p[i] specifies the coefficients + used in .Q_A(z) while q[i] specifies the coefficients used + in .P_A(z) */ + + for (i = 0; i < LPC_HALFORDER; i++){ + p[i] = (float)cos(TWO_PI * freq[2 * i]); + q[i] = (float)cos(TWO_PI * freq[2 * i + 1]); + } + + a[0] = 0.25; + b[0] = 0.25; + + for (i = 0; i < LPC_HALFORDER; i++){ + a[i + 1] = a[i] - 2 * p[i] * a1[i] + a2[i]; + b[i + 1] = b[i] - 2 * q[i] * b1[i] + b2[i]; + a2[i] = a1[i]; + a1[i] = a[i]; + b2[i] = b1[i]; + b1[i] = b[i]; + } + + for (j = 0; j < LPC_FILTERORDER; j++){ + + if (j == 0) { + a[0] = 0.25; + b[0] = -0.25; + } else { + a[0] = b[0] = 0.0; + } + + for (i = 0; i < LPC_HALFORDER; i++){ + a[i + 1] = a[i] - 2 * p[i] * a1[i] + a2[i]; + b[i + 1] = b[i] - 2 * q[i] * b1[i] + b2[i]; + a2[i] = a1[i]; + a1[i] = a[i]; + b2[i] = b1[i]; + b1[i] = b[i]; + } + + a_coef[j + 1] = 2 * (a[LPC_HALFORDER] + b[LPC_HALFORDER]); + } + + a_coef[0] = 1.0; +} + + |