Asterisk.org: Developer Documentation (6 Aug 2006)

00108 {
00109    int i;
00110    int j;
00111    int acc;
00112    int min_acc;
00113    int pitch;
00114 
00115    pitch = min_pitch;
00116    min_acc = INT_MAX;
00117    for (i = max_pitch;  i <= min_pitch;  i++) {
00118       acc = 0;
00119       for (j = 0;  j < len;  j++)
00120          acc += abs(amp[i + j] - amp[j]);
00121       if (acc < min_acc) {
00122          min_acc = acc;
00123          pitch = i;
00124       }
00125    }
00126    return pitch;
00127 }

00062 {
00063    if (damp > 32767.0)
00064       return  INT16_MAX;
00065    if (damp < -32768.0)
00066       return  INT16_MIN;
00067    return (int16_t) rint(damp);
00068 }

00094 {
00095    int16_t tmp[PLC_HISTORY_LEN];
00096 
00097    if (s->buf_ptr == 0)
00098       return;
00099    memcpy(tmp, s->history, sizeof(int16_t)*s->buf_ptr);
00100    memcpy(s->history, s->history + s->buf_ptr, sizeof(int16_t)*(PLC_HISTORY_LEN - s->buf_ptr));
00101    memcpy(s->history + PLC_HISTORY_LEN - s->buf_ptr, tmp, sizeof(int16_t)*s->buf_ptr);
00102    s->buf_ptr = 0;
00103 }

00175 {
00176    int i;
00177    int pitch_overlap;
00178    float old_step;
00179    float new_step;
00180    float old_weight;
00181    float new_weight;
00182    float gain;
00183    int16_t *orig_amp;
00184    int orig_len;
00185 
00186    orig_amp = amp;
00187    orig_len = len;
00188    if (s->missing_samples == 0) {
00189       /* As the gap in real speech starts we need to assess the last known pitch,
00190          and prepare the synthetic data we will use for fill-in */
00191       normalise_history(s);
00192       s->pitch = amdf_pitch(PLC_PITCH_MIN, PLC_PITCH_MAX, s->history + PLC_HISTORY_LEN - CORRELATION_SPAN - PLC_PITCH_MIN, CORRELATION_SPAN);
00193       /* We overlap a 1/4 wavelength */
00194       pitch_overlap = s->pitch >> 2;
00195       /* Cook up a single cycle of pitch, using a single of the real signal with 1/4
00196          cycle OLA'ed to make the ends join up nicely */
00197       /* The first 3/4 of the cycle is a simple copy */
00198       for (i = 0;  i < s->pitch - pitch_overlap;  i++)
00199          s->pitchbuf[i] = s->history[PLC_HISTORY_LEN - s->pitch + i];
00200       /* The last 1/4 of the cycle is overlapped with the end of the previous cycle */
00201       new_step = 1.0/pitch_overlap;
00202       new_weight = new_step;
00203       for (  ;  i < s->pitch;  i++) {
00204          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;
00205          new_weight += new_step;
00206       }
00207       /* We should now be ready to fill in the gap with repeated, decaying cycles
00208          of what is in pitchbuf */
00209 
00210       /* We need to OLA the first 1/4 wavelength of the synthetic data, to smooth
00211          it into the previous real data. To avoid the need to introduce a delay
00212          in the stream, reverse the last 1/4 wavelength, and OLA with that. */
00213       gain = 1.0;
00214       new_step = 1.0/pitch_overlap;
00215       old_step = new_step;
00216       new_weight = new_step;
00217       old_weight = 1.0 - new_step;
00218       for (i = 0;  i < pitch_overlap;  i++) {
00219          amp[i] = fsaturate(old_weight*s->history[PLC_HISTORY_LEN - 1 - i] + new_weight*s->pitchbuf[i]);
00220          new_weight += new_step;
00221          old_weight -= old_step;
00222          if (old_weight < 0.0)
00223             old_weight = 0.0;
00224       }
00225       s->pitch_offset = i;
00226    } else {
00227       gain = 1.0 - s->missing_samples*ATTENUATION_INCREMENT;
00228       i = 0;
00229    }
00230    for (  ;  gain > 0.0  &&  i < len;  i++) {
00231       amp[i] = s->pitchbuf[s->pitch_offset]*gain;
00232       gain -= ATTENUATION_INCREMENT;
00233       if (++s->pitch_offset >= s->pitch)
00234          s->pitch_offset = 0;
00235    }
00236    for (  ;  i < len;  i++)
00237       amp[i] = 0;
00238    s->missing_samples += orig_len;
00239    save_history(s, amp, len);
00240    return len;
00241 }

00246 {
00247    memset(s, 0, sizeof(*s));
00248    return s;
00249 }

00132 {
00133    int i;
00134    int pitch_overlap;
00135    float old_step;
00136    float new_step;
00137    float old_weight;
00138    float new_weight;
00139    float gain;
00140    
00141    if (s->missing_samples) {
00142       /* Although we have a real signal, we need to smooth it to fit well
00143       with the synthetic signal we used for the previous block */
00144 
00145       /* The start of the real data is overlapped with the next 1/4 cycle
00146          of the synthetic data. */
00147       pitch_overlap = s->pitch >> 2;
00148       if (pitch_overlap > len)
00149          pitch_overlap = len;
00150       gain = 1.0 - s->missing_samples*ATTENUATION_INCREMENT;
00151       if (gain < 0.0)
00152          gain = 0.0;
00153       new_step = 1.0/pitch_overlap;
00154       old_step = new_step*gain;
00155       new_weight = new_step;
00156       old_weight = (1.0 - new_step)*gain;
00157       for (i = 0;  i < pitch_overlap;  i++) {
00158          amp[i] = fsaturate(old_weight*s->pitchbuf[s->pitch_offset] + new_weight*amp[i]);
00159          if (++s->pitch_offset >= s->pitch)
00160             s->pitch_offset = 0;
00161          new_weight += new_step;
00162          old_weight -= old_step;
00163          if (old_weight < 0.0)
00164             old_weight = 0.0;
00165       }
00166       s->missing_samples = 0;
00167    }
00168    save_history(s, amp, len);
00169    return len;
00170 }

00071 {
00072    if (len >= PLC_HISTORY_LEN) {
00073       /* Just keep the last part of the new data, starting at the beginning of the buffer */
00074        memcpy(s->history, buf + len - PLC_HISTORY_LEN, sizeof(int16_t)*PLC_HISTORY_LEN);
00075       s->buf_ptr = 0;
00076       return;
00077    }
00078    if (s->buf_ptr + len > PLC_HISTORY_LEN) {
00079       /* Wraps around - must break into two sections */
00080       memcpy(s->history + s->buf_ptr, buf, sizeof(int16_t)*(PLC_HISTORY_LEN - s->buf_ptr));
00081       len -= (PLC_HISTORY_LEN - s->buf_ptr);
00082       memcpy(s->history, buf + (PLC_HISTORY_LEN - s->buf_ptr), sizeof(int16_t)*len);
00083       s->buf_ptr = len;
00084       return;
00085    }
00086    /* Can use just one section */
00087    memcpy(s->history + s->buf_ptr, buf, sizeof(int16_t)*len);
00088    s->buf_ptr += len;
00089 }


Defines
#define	ATTENUATION_INCREMENT 0.0025
#define	FALSE 0
#define	INT16_MAX (32767)
#define	INT16_MIN (-32767-1)
#define	ms_to_samples(t) (((t)*SAMPLE_RATE)/1000)
#define	TRUE (!FALSE)
Functions
static int __inline__	amdf_pitch (int min_pitch, int max_pitch, int16_t amp[], int len)
static int16_t	fsaturate (double damp)
static void	normalise_history (plc_state_t *s)
int	plc_fillin (plc_state_t *s, int16_t amp[], int len)
	Fill-in a block of missing audio samples.
plc_state_t *	plc_init (plc_state_t *s)
	Process a block of received V.29 modem audio samples.
int	plc_rx (plc_state_t *s, int16_t amp[], int len)
	Process a block of received audio samples.
static void	save_history (plc_state_t s, int16_t buf, int len)

Asterisk developer's documentation

plc.c File Reference

Defines

Functions

Detailed Description

Define Documentation

Function Documentation