1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
/***********************************************************************
Copyright (c) 2006-2012, Skype Limited. All rights reserved.
Redistribution and use in source and binary forms, with or without
modification, (subject to the limitations in the disclaimer below)
are permitted provided that the following conditions are met:
- Redistributions of source code must retain the above copyright notice,
this list of conditions and the following disclaimer.
- Redistributions in binary form must reproduce the above copyright
notice, this list of conditions and the following disclaimer in the
documentation and/or other materials provided with the distribution.
- Neither the name of Skype Limited, nor the names of specific
contributors, may be used to endorse or promote products derived from
this software without specific prior written permission.
NO EXPRESS OR IMPLIED LICENSES TO ANY PARTY'S PATENT RIGHTS ARE GRANTED
BY THIS LICENSE. THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND
CONTRIBUTORS ''AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING,
BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND
FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON
ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
(INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
***********************************************************************/
/*
Elliptic/Cauer filters designed with 0.1 dB passband ripple,
80 dB minimum stopband attenuation, and
[0.95 : 0.15 : 0.35] normalized cut off frequencies.
*/
#include "SKP_Silk_main.h"
#if SWITCH_TRANSITION_FILTERING
/* Helper function, that interpolates the filter taps */
SKP_INLINE void SKP_Silk_LP_interpolate_filter_taps(
SKP_int32 B_Q28[ TRANSITION_NB ],
SKP_int32 A_Q28[ TRANSITION_NA ],
const SKP_int ind,
const SKP_int32 fac_Q16
)
{
SKP_int nb, na;
if( ind < TRANSITION_INT_NUM - 1 ) {
if( fac_Q16 > 0 ) {
if( fac_Q16 == SKP_SAT16( fac_Q16 ) ) { /* fac_Q16 is in range of a 16-bit int */
/* Piece-wise linear interpolation of B and A */
for( nb = 0; nb < TRANSITION_NB; nb++ ) {
B_Q28[ nb ] = SKP_SMLAWB(
SKP_Silk_Transition_LP_B_Q28[ ind ][ nb ],
SKP_Silk_Transition_LP_B_Q28[ ind + 1 ][ nb ] -
SKP_Silk_Transition_LP_B_Q28[ ind ][ nb ],
fac_Q16 );
}
for( na = 0; na < TRANSITION_NA; na++ ) {
A_Q28[ na ] = SKP_SMLAWB(
SKP_Silk_Transition_LP_A_Q28[ ind ][ na ],
SKP_Silk_Transition_LP_A_Q28[ ind + 1 ][ na ] -
SKP_Silk_Transition_LP_A_Q28[ ind ][ na ],
fac_Q16 );
}
} else if( fac_Q16 == ( 1 << 15 ) ) { /* Neither fac_Q16 nor ( ( 1 << 16 ) - fac_Q16 ) is in range of a 16-bit int */
/* Piece-wise linear interpolation of B and A */
for( nb = 0; nb < TRANSITION_NB; nb++ ) {
B_Q28[ nb ] = SKP_RSHIFT(
SKP_Silk_Transition_LP_B_Q28[ ind ][ nb ] +
SKP_Silk_Transition_LP_B_Q28[ ind + 1 ][ nb ],
1 );
}
for( na = 0; na < TRANSITION_NA; na++ ) {
A_Q28[ na ] = SKP_RSHIFT(
SKP_Silk_Transition_LP_A_Q28[ ind ][ na ] +
SKP_Silk_Transition_LP_A_Q28[ ind + 1 ][ na ],
1 );
}
} else { /* ( ( 1 << 16 ) - fac_Q16 ) is in range of a 16-bit int */
SKP_assert( ( ( 1 << 16 ) - fac_Q16 ) == SKP_SAT16( ( ( 1 << 16 ) - fac_Q16) ) );
/* Piece-wise linear interpolation of B and A */
for( nb = 0; nb < TRANSITION_NB; nb++ ) {
B_Q28[ nb ] = SKP_SMLAWB(
SKP_Silk_Transition_LP_B_Q28[ ind + 1 ][ nb ],
SKP_Silk_Transition_LP_B_Q28[ ind ][ nb ] -
SKP_Silk_Transition_LP_B_Q28[ ind + 1 ][ nb ],
( 1 << 16 ) - fac_Q16 );
}
for( na = 0; na < TRANSITION_NA; na++ ) {
A_Q28[ na ] = SKP_SMLAWB(
SKP_Silk_Transition_LP_A_Q28[ ind + 1 ][ na ],
SKP_Silk_Transition_LP_A_Q28[ ind ][ na ] -
SKP_Silk_Transition_LP_A_Q28[ ind + 1 ][ na ],
( 1 << 16 ) - fac_Q16 );
}
}
} else {
SKP_memcpy( B_Q28, SKP_Silk_Transition_LP_B_Q28[ ind ], TRANSITION_NB * sizeof( SKP_int32 ) );
SKP_memcpy( A_Q28, SKP_Silk_Transition_LP_A_Q28[ ind ], TRANSITION_NA * sizeof( SKP_int32 ) );
}
} else {
SKP_memcpy( B_Q28, SKP_Silk_Transition_LP_B_Q28[ TRANSITION_INT_NUM - 1 ], TRANSITION_NB * sizeof( SKP_int32 ) );
SKP_memcpy( A_Q28, SKP_Silk_Transition_LP_A_Q28[ TRANSITION_INT_NUM - 1 ], TRANSITION_NA * sizeof( SKP_int32 ) );
}
}
/* Low-pass filter with variable cutoff frequency based on */
/* piece-wise linear interpolation between elliptic filters */
/* Start by setting psEncC->transition_frame_no = 1; */
/* Deactivate by setting psEncC->transition_frame_no = 0; */
void SKP_Silk_LP_variable_cutoff(
SKP_Silk_LP_state *psLP, /* I/O LP filter state */
SKP_int16 *out, /* O Low-pass filtered output signal */
const SKP_int16 *in, /* I Input signal */
const SKP_int frame_length /* I Frame length */
)
{
SKP_int32 B_Q28[ TRANSITION_NB ], A_Q28[ TRANSITION_NA ], fac_Q16 = 0;
SKP_int ind = 0;
SKP_assert( psLP->transition_frame_no >= 0 );
SKP_assert( ( ( ( psLP->transition_frame_no <= TRANSITION_FRAMES_DOWN ) && ( psLP->mode == 0 ) ) ||
( ( psLP->transition_frame_no <= TRANSITION_FRAMES_UP ) && ( psLP->mode == 1 ) ) ) );
/* Interpolate filter coefficients if needed */
if( psLP->transition_frame_no > 0 ) {
if( psLP->mode == 0 ) {
if( psLP->transition_frame_no < TRANSITION_FRAMES_DOWN ) {
/* Calculate index and interpolation factor for interpolation */
#if( TRANSITION_INT_STEPS_DOWN == 32 )
fac_Q16 = SKP_LSHIFT( psLP->transition_frame_no, 16 - 5 );
#else
fac_Q16 = SKP_DIV32_16( SKP_LSHIFT( psLP->transition_frame_no, 16 ), TRANSITION_INT_STEPS_DOWN );
#endif
ind = SKP_RSHIFT( fac_Q16, 16 );
fac_Q16 -= SKP_LSHIFT( ind, 16 );
SKP_assert( ind >= 0 );
SKP_assert( ind < TRANSITION_INT_NUM );
/* Interpolate filter coefficients */
SKP_Silk_LP_interpolate_filter_taps( B_Q28, A_Q28, ind, fac_Q16 );
/* Increment transition frame number for next frame */
psLP->transition_frame_no++;
} else {
SKP_assert( psLP->transition_frame_no == TRANSITION_FRAMES_DOWN );
/* End of transition phase */
SKP_Silk_LP_interpolate_filter_taps( B_Q28, A_Q28, TRANSITION_INT_NUM - 1, 0 );
}
} else {
SKP_assert( psLP->mode == 1 );
if( psLP->transition_frame_no < TRANSITION_FRAMES_UP ) {
/* Calculate index and interpolation factor for interpolation */
#if( TRANSITION_INT_STEPS_UP == 64 )
fac_Q16 = SKP_LSHIFT( TRANSITION_FRAMES_UP - psLP->transition_frame_no, 16 - 6 );
#else
fac_Q16 = SKP_DIV32_16( SKP_LSHIFT( TRANSITION_FRAMES_UP - psLP->transition_frame_no, 16 ), TRANSITION_INT_STEPS_UP );
#endif
ind = SKP_RSHIFT( fac_Q16, 16 );
fac_Q16 -= SKP_LSHIFT( ind, 16 );
SKP_assert( ind >= 0 );
SKP_assert( ind < TRANSITION_INT_NUM );
/* Interpolate filter coefficients */
SKP_Silk_LP_interpolate_filter_taps( B_Q28, A_Q28, ind, fac_Q16 );
/* Increment transition frame number for next frame */
psLP->transition_frame_no++;
} else {
SKP_assert( psLP->transition_frame_no == TRANSITION_FRAMES_UP );
/* End of transition phase */
SKP_Silk_LP_interpolate_filter_taps( B_Q28, A_Q28, 0, 0 );
}
}
}
if( psLP->transition_frame_no > 0 ) {
/* ARMA low-pass filtering */
SKP_assert( TRANSITION_NB == 3 && TRANSITION_NA == 2 );
SKP_Silk_biquad_alt( in, B_Q28, A_Q28, psLP->In_LP_State, out, frame_length );
} else {
/* Instead of using the filter, copy input directly to output */
SKP_memcpy( out, in, frame_length * sizeof( SKP_int16 ) );
}
}
#endif