2 * Asterisk -- An open source telephony toolkit.
4 * Written by Steve Underwood <steveu@coppice.org>
6 * Copyright (C) 2004 Steve Underwood
10 * See http://www.asterisk.org for more information about
11 * the Asterisk project. Please do not directly contact
12 * any of the maintainers of this project for assistance;
13 * the project provides a web site, mailing lists and IRC
14 * channels for your use.
16 * This program is free software, distributed under the terms of
17 * the GNU General Public License Version 2. See the LICENSE file
18 * at the top of the source tree.
20 * This version may be optionally licenced under the GNU LGPL licence.
22 * A license has been granted to Digium (via disclaimer) for the use of
28 * \brief SpanDSP - a series of DSP components for telephony
30 * \author Steve Underwood <steveu@coppice.org>
35 ASTERISK_FILE_VERSION(__FILE__
, "$Revision$")
39 #include "asterisk/plc.h"
48 #if !defined(INT16_MAX)
49 #define INT16_MAX (32767)
50 #define INT16_MIN (-32767-1)
53 /* We do a straight line fade to zero volume in 50ms when we are filling in for missing data. */
54 #define ATTENUATION_INCREMENT 0.0025 /* Attenuation per sample */
56 #define ms_to_samples(t) (((t)*DEFAULT_SAMPLE_RATE)/1000)
58 static inline int16_t fsaturate(double damp
)
64 return (int16_t) rint(damp
);
67 static void save_history(plc_state_t
*s
, int16_t *buf
, int len
)
69 if (len
>= PLC_HISTORY_LEN
) {
70 /* Just keep the last part of the new data, starting at the beginning of the buffer */
71 memcpy(s
->history
, buf
+ len
- PLC_HISTORY_LEN
, sizeof(int16_t) * PLC_HISTORY_LEN
);
75 if (s
->buf_ptr
+ len
> PLC_HISTORY_LEN
) {
76 /* Wraps around - must break into two sections */
77 memcpy(s
->history
+ s
->buf_ptr
, buf
, sizeof(int16_t) * (PLC_HISTORY_LEN
- s
->buf_ptr
));
78 len
-= (PLC_HISTORY_LEN
- s
->buf_ptr
);
79 memcpy(s
->history
, buf
+ (PLC_HISTORY_LEN
- s
->buf_ptr
), sizeof(int16_t)*len
);
83 /* Can use just one section */
84 memcpy(s
->history
+ s
->buf_ptr
, buf
, sizeof(int16_t)*len
);
88 /*- End of function --------------------------------------------------------*/
90 static void normalise_history(plc_state_t
*s
)
92 int16_t tmp
[PLC_HISTORY_LEN
];
96 memcpy(tmp
, s
->history
, sizeof(int16_t)*s
->buf_ptr
);
97 memcpy(s
->history
, s
->history
+ s
->buf_ptr
, sizeof(int16_t) * (PLC_HISTORY_LEN
- s
->buf_ptr
));
98 memcpy(s
->history
+ PLC_HISTORY_LEN
- s
->buf_ptr
, tmp
, sizeof(int16_t) * s
->buf_ptr
);
102 /*- End of function --------------------------------------------------------*/
104 static int __inline__
amdf_pitch(int min_pitch
, int max_pitch
, int16_t amp
[], int len
)
114 for (i
= max_pitch
; i
<= min_pitch
; i
++) {
116 for (j
= 0; j
< len
; j
++)
117 acc
+= abs(amp
[i
+ j
] - amp
[j
]);
126 /*- End of function --------------------------------------------------------*/
128 int plc_rx(plc_state_t
*s
, int16_t amp
[], int len
)
138 if (s
->missing_samples
) {
139 /* Although we have a real signal, we need to smooth it to fit well
140 with the synthetic signal we used for the previous block */
142 /* The start of the real data is overlapped with the next 1/4 cycle
143 of the synthetic data. */
144 pitch_overlap
= s
->pitch
>> 2;
145 if (pitch_overlap
> len
)
147 gain
= 1.0 - s
->missing_samples
*ATTENUATION_INCREMENT
;
150 new_step
= 1.0/pitch_overlap
;
151 old_step
= new_step
*gain
;
152 new_weight
= new_step
;
153 old_weight
= (1.0 - new_step
)*gain
;
154 for (i
= 0; i
< pitch_overlap
; i
++) {
155 amp
[i
] = fsaturate(old_weight
* s
->pitchbuf
[s
->pitch_offset
] + new_weight
* amp
[i
]);
156 if (++s
->pitch_offset
>= s
->pitch
)
158 new_weight
+= new_step
;
159 old_weight
-= old_step
;
160 if (old_weight
< 0.0)
163 s
->missing_samples
= 0;
165 save_history(s
, amp
, len
);
169 /*- End of function --------------------------------------------------------*/
171 int plc_fillin(plc_state_t
*s
, int16_t amp
[], int len
)
185 if (s
->missing_samples
== 0) {
186 /* As the gap in real speech starts we need to assess the last known pitch,
187 and prepare the synthetic data we will use for fill-in */
188 normalise_history(s
);
189 s
->pitch
= amdf_pitch(PLC_PITCH_MIN
, PLC_PITCH_MAX
, s
->history
+ PLC_HISTORY_LEN
- CORRELATION_SPAN
- PLC_PITCH_MIN
, CORRELATION_SPAN
);
190 /* We overlap a 1/4 wavelength */
191 pitch_overlap
= s
->pitch
>> 2;
192 /* Cook up a single cycle of pitch, using a single of the real signal with 1/4
193 cycle OLA'ed to make the ends join up nicely */
194 /* The first 3/4 of the cycle is a simple copy */
195 for (i
= 0; i
< s
->pitch
- pitch_overlap
; i
++)
196 s
->pitchbuf
[i
] = s
->history
[PLC_HISTORY_LEN
- s
->pitch
+ i
];
197 /* The last 1/4 of the cycle is overlapped with the end of the previous cycle */
198 new_step
= 1.0/pitch_overlap
;
199 new_weight
= new_step
;
200 for ( ; i
< s
->pitch
; i
++) {
201 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
;
202 new_weight
+= new_step
;
204 /* We should now be ready to fill in the gap with repeated, decaying cycles
205 of what is in pitchbuf */
207 /* We need to OLA the first 1/4 wavelength of the synthetic data, to smooth
208 it into the previous real data. To avoid the need to introduce a delay
209 in the stream, reverse the last 1/4 wavelength, and OLA with that. */
211 new_step
= 1.0 / pitch_overlap
;
213 new_weight
= new_step
;
214 old_weight
= 1.0 - new_step
;
215 for (i
= 0; i
< pitch_overlap
; i
++) {
216 amp
[i
] = fsaturate(old_weight
* s
->history
[PLC_HISTORY_LEN
- 1 - i
] + new_weight
* s
->pitchbuf
[i
]);
217 new_weight
+= new_step
;
218 old_weight
-= old_step
;
219 if (old_weight
< 0.0)
224 gain
= 1.0 - s
->missing_samples
*ATTENUATION_INCREMENT
;
227 for ( ; gain
> 0.0 && i
< len
; i
++) {
228 amp
[i
] = s
->pitchbuf
[s
->pitch_offset
] * gain
;
229 gain
-= ATTENUATION_INCREMENT
;
230 if (++s
->pitch_offset
>= s
->pitch
)
233 for ( ; i
< len
; i
++)
235 s
->missing_samples
+= orig_len
;
236 save_history(s
, amp
, len
);
240 /*- End of function --------------------------------------------------------*/
242 plc_state_t
*plc_init(plc_state_t
*s
)
244 memset(s
, 0, sizeof(*s
));
247 /*- End of function --------------------------------------------------------*/
248 /*- End of file ------------------------------------------------------------*/