/* * SpanDSP - a series of DSP components for telephony * * plc.c * * Written by Steve Underwood * * Copyright (C) 2004 Steve Underwood * * All rights reserved. * * This program is free software; you can redistribute it and/or modify * it under the terms of the GNU General Public License as published by * the Free Software Foundation; either version 2 of the License, or * (at your option) any later version. * * This program is distributed in the hope that it will be useful, * but WITHOUT ANY WARRANTY; without even the implied warranty of * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the * GNU General Public License for more details. * * You should have received a copy of the GNU General Public License * along with this program; if not, write to the Free Software * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA. * * This version may be optionally licenced under the GNU LGPL licence. * This version is disclaimed to DIGIUM for inclusion in the Asterisk project. */ /*! \file */ #include #include #include #include #include #include "asterisk/plc.h" #if !defined(FALSE) #define FALSE 0 #endif #if !defined(TRUE) #define TRUE (!FALSE) #endif #if !defined(INT16_MAX) #define INT16_MAX (32767) #define INT16_MIN (-32767-1) #endif /* We do a straight line fade to zero volume in 50ms when we are filling in for missing data. */ #define ATTENUATION_INCREMENT 0.0025 /* Attenuation per sample */ #define ms_to_samples(t) (((t)*SAMPLE_RATE)/1000) static inline int16_t fsaturate(double damp) { if (damp > 32767.0) return INT16_MAX; if (damp < -32768.0) return INT16_MIN; return (int16_t) rint(damp); } static void save_history(plc_state_t *s, int16_t *buf, int len) { if (len >= PLC_HISTORY_LEN) { /* Just keep the last part of the new data, starting at the beginning of the buffer */ memcpy(s->history, buf + len - PLC_HISTORY_LEN, sizeof(int16_t)*PLC_HISTORY_LEN); s->buf_ptr = 0; return; } if (s->buf_ptr + len > PLC_HISTORY_LEN) { /* Wraps around - must break into two sections */ memcpy(s->history + s->buf_ptr, buf, sizeof(int16_t)*(PLC_HISTORY_LEN - s->buf_ptr)); len -= (PLC_HISTORY_LEN - s->buf_ptr); memcpy(s->history, buf + (PLC_HISTORY_LEN - s->buf_ptr), sizeof(int16_t)*len); s->buf_ptr = len; return; } /* Can use just one section */ memcpy(s->history + s->buf_ptr, buf, sizeof(int16_t)*len); s->buf_ptr += len; } /*- End of function --------------------------------------------------------*/ static void normalise_history(plc_state_t *s) { int16_t tmp[PLC_HISTORY_LEN]; if (s->buf_ptr == 0) return; memcpy(tmp, s->history, sizeof(int16_t)*s->buf_ptr); memcpy(s->history, s->history + s->buf_ptr, sizeof(int16_t)*(PLC_HISTORY_LEN - s->buf_ptr)); memcpy(s->history + PLC_HISTORY_LEN - s->buf_ptr, tmp, sizeof(int16_t)*s->buf_ptr); s->buf_ptr = 0; } /*- End of function --------------------------------------------------------*/ static int __inline__ amdf_pitch(int min_pitch, int max_pitch, int16_t amp[], int len) { int i; int j; int acc; int min_acc; int pitch; pitch = min_pitch; min_acc = INT_MAX; for (i = max_pitch; i <= min_pitch; i++) { acc = 0; for (j = 0; j < len; j++) acc += abs(amp[i + j] - amp[j]); if (acc < min_acc) { min_acc = acc; pitch = i; } } return pitch; } /*- End of function --------------------------------------------------------*/ int plc_rx(plc_state_t *s, int16_t amp[], int len) { int i; int pitch_overlap; float old_step; float new_step; float old_weight; float new_weight; float gain; if (s->missing_samples) { /* Although we have a real signal, we need to smooth it to fit well with the synthetic signal we used for the previous block */ /* The start of the real data is overlapped with the next 1/4 cycle of the synthetic data. */ pitch_overlap = s->pitch >> 2; if (pitch_overlap > len) pitch_overlap = len; gain = 1.0 - s->missing_samples*ATTENUATION_INCREMENT; if (gain < 0.0) gain = 0.0; new_step = 1.0/pitch_overlap; old_step = new_step*gain; new_weight = new_step; old_weight = (1.0 - new_step)*gain; for (i = 0; i < pitch_overlap; i++) { amp[i] = fsaturate(old_weight*s->pitchbuf[s->pitch_offset] + new_weight*amp[i]); if (++s->pitch_offset >= s->pitch) s->pitch_offset = 0; new_weight += new_step; old_weight -= old_step; if (old_weight < 0.0) old_weight = 0.0; } s->missing_samples = 0; } save_history(s, amp, len); return len; } /*- End of function --------------------------------------------------------*/ int plc_fillin(plc_state_t *s, int16_t amp[], int len) { int i; int pitch_overlap; float old_step; float new_step; float old_weight; float new_weight; float gain; int16_t *orig_amp; int orig_len; orig_amp = amp; orig_len = len; if (s->missing_samples == 0) { /* As the gap in real speech starts we need to assess the last known pitch, and prepare the synthetic data we will use for fill-in */ normalise_history(s); s->pitch = amdf_pitch(PLC_PITCH_MIN, PLC_PITCH_MAX, s->history + PLC_HISTORY_LEN - CORRELATION_SPAN - PLC_PITCH_MIN, CORRELATION_SPAN); /* We overlap a 1/4 wavelength */ pitch_overlap = s->pitch >> 2; /* Cook up a single cycle of pitch, using a single of the real signal with 1/4 cycle OLA'ed to make the ends join up nicely */ /* The first 3/4 of the cycle is a simple copy */ for (i = 0; i < s->pitch - pitch_overlap; i++) s->pitchbuf[i] = s->history[PLC_HISTORY_LEN - s->pitch + i]; /* The last 1/4 of the cycle is overlapped with the end of the previous cycle */ new_step = 1.0/pitch_overlap; new_weight = new_step; for ( ; i < s->pitch; i++) { s->pitchbuf[i] = s->history[PLC_HISTORY_LEN - s->pitch + i]*(1.0 - new_weight) + s->history[PLC_HISTORY_LEN - 2*s->pitch + i]*new_weight; new_weight += new_step; } /* We should now be ready to fill in the gap with repeated, decaying cycles of what is in pitchbuf */ /* We need to OLA the first 1/4 wavelength of the synthetic data, to smooth it into the previous real data. To avoid the need to introduce a delay in the stream, reverse the last 1/4 wavelength, and OLA with that. */ gain = 1.0; new_step = 1.0/pitch_overlap; old_step = new_step; new_weight = new_step; old_weight = 1.0 - new_step; for (i = 0; i < pitch_overlap; i++) { amp[i] = fsaturate(old_weight*s->history[PLC_HISTORY_LEN - 1 - i] + new_weight*s->pitchbuf[i]); new_weight += new_step; old_weight -= old_step; if (old_weight < 0.0) old_weight = 0.0; } s->pitch_offset = i; } else { gain = 1.0 - s->missing_samples*ATTENUATION_INCREMENT; i = 0; } for ( ; gain > 0.0 && i < len; i++) { amp[i] = s->pitchbuf[s->pitch_offset]*gain; gain -= ATTENUATION_INCREMENT; if (++s->pitch_offset >= s->pitch) s->pitch_offset = 0; } for ( ; i < len; i++) amp[i] = 0; s->missing_samples += orig_len; save_history(s, amp, len); return len; } /*- End of function --------------------------------------------------------*/ plc_state_t *plc_init(plc_state_t *s) { memset(s, 0, sizeof(*s)); return s; } /*- End of function --------------------------------------------------------*/ /*- End of file ------------------------------------------------------------*/