3 * Copyright (c) 2006 Justin Ruggles <justin.ruggles@gmail.com>
5 * This file is part of FFmpeg.
7 * FFmpeg is free software; you can redistribute it and/or
8 * modify it under the terms of the GNU Lesser General Public
9 * License as published by the Free Software Foundation; either
10 * version 2.1 of the License, or (at your option) any later version.
12 * FFmpeg is distributed in the hope that it will be useful,
13 * but WITHOUT ANY WARRANTY; without even the implied warranty of
14 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
15 * Lesser General Public License for more details.
17 * You should have received a copy of the GNU Lesser General Public
18 * License along with FFmpeg; if not, write to the Free Software
19 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
26 #include "libavutil/avassert.h"
27 #include "libavutil/lls.h"
29 #define ORDER_METHOD_EST 0
30 #define ORDER_METHOD_2LEVEL 1
31 #define ORDER_METHOD_4LEVEL 2
32 #define ORDER_METHOD_8LEVEL 3
33 #define ORDER_METHOD_SEARCH 4
34 #define ORDER_METHOD_LOG 5
36 #define MIN_LPC_ORDER 1
37 #define MAX_LPC_ORDER 32
43 FF_LPC_TYPE_DEFAULT
= -1, ///< use the codec default LPC type
44 FF_LPC_TYPE_NONE
= 0, ///< do not use LPC prediction or use all zero coefficients
45 FF_LPC_TYPE_FIXED
= 1, ///< fixed LPC coefficients
46 FF_LPC_TYPE_LEVINSON
= 2, ///< Levinson-Durbin recursion
47 FF_LPC_TYPE_CHOLESKY
= 3, ///< Cholesky factorization
48 FF_LPC_TYPE_NB
, ///< Not part of ABI
51 typedef struct LPCContext
{
54 enum FFLPCType lpc_type
;
55 double *windowed_buffer
;
56 double *windowed_samples
;
59 * Apply a Welch window to an array of input samples.
60 * The output samples have the same scale as the input, but are in double
62 * @param data input samples
63 * @param len number of input samples
64 * @param w_data output samples
66 void (*lpc_apply_welch_window
)(const int32_t *data
, int len
,
69 * Perform autocorrelation on input samples with delay of 0 to lag.
70 * @param data input samples.
71 * constraints: no alignment needed, but must have at
72 * least lag*sizeof(double) valid bytes preceding it, and
73 * size must be at least (len+1)*sizeof(double) if data is
74 * 16-byte aligned or (len+2)*sizeof(double) if data is
76 * @param len number of input samples to process
77 * @param lag maximum delay to calculate
78 * @param autoc output autocorrelation coefficients.
79 * constraints: array size must be at least lag+1.
81 void (*lpc_compute_autocorr
)(const double *data
, int len
, int lag
,
84 // TODO: these should be allocated to reduce ABI compatibility issues
85 LLSModel lls_models
[2];
90 * Calculate LPC coefficients for multiple orders
92 int ff_lpc_calc_coefs(LPCContext
*s
,
93 const int32_t *samples
, int blocksize
, int min_order
,
94 int max_order
, int precision
,
95 int32_t coefs
[][MAX_LPC_ORDER
], int *shift
,
96 enum FFLPCType lpc_type
, int lpc_passes
,
97 int omethod
, int max_shift
, int zero_shift
);
99 int ff_lpc_calc_ref_coefs(LPCContext
*s
,
100 const int32_t *samples
, int order
, double *ref
);
103 * Initialize LPCContext.
105 int ff_lpc_init(LPCContext
*s
, int blocksize
, int max_order
,
106 enum FFLPCType lpc_type
);
107 void ff_lpc_init_x86(LPCContext
*s
);
110 * Uninitialize LPCContext.
112 void ff_lpc_end(LPCContext
*s
);
114 #ifdef LPC_USE_DOUBLE
115 #define LPC_TYPE double
117 #define LPC_TYPE float
122 * Produces reflection coefficients from autocorrelation data.
124 static inline void compute_ref_coefs(const LPC_TYPE
*autoc
, int max_order
,
125 LPC_TYPE
*ref
, LPC_TYPE
*error
)
129 LPC_TYPE gen0
[MAX_LPC_ORDER
], gen1
[MAX_LPC_ORDER
];
131 for (i
= 0; i
< max_order
; i
++)
132 gen0
[i
] = gen1
[i
] = autoc
[i
+ 1];
135 ref
[0] = -gen1
[0] / err
;
136 err
+= gen1
[0] * ref
[0];
139 for (i
= 1; i
< max_order
; i
++) {
140 for (j
= 0; j
< max_order
- i
; j
++) {
141 gen1
[j
] = gen1
[j
+ 1] + ref
[i
- 1] * gen0
[j
];
142 gen0
[j
] = gen1
[j
+ 1] * ref
[i
- 1] + gen0
[j
];
144 ref
[i
] = -gen1
[0] / err
;
145 err
+= gen1
[0] * ref
[i
];
152 * Levinson-Durbin recursion.
153 * Produce LPC coefficients from autocorrelation data.
155 static inline int compute_lpc_coefs(const LPC_TYPE
*autoc
, int max_order
,
156 LPC_TYPE
*lpc
, int lpc_stride
, int fail
,
161 LPC_TYPE
*lpc_last
= lpc
;
163 av_assert2(normalize
|| !fail
);
168 if (fail
&& (autoc
[max_order
- 1] == 0 || err
<= 0))
171 for(i
=0; i
<max_order
; i
++) {
172 LPC_TYPE r
= -autoc
[i
];
176 r
-= lpc_last
[j
] * autoc
[i
-j
-1];
179 err
*= 1.0 - (r
* r
);
184 for(j
=0; j
< (i
+1)>>1; j
++) {
185 LPC_TYPE f
= lpc_last
[ j
];
186 LPC_TYPE b
= lpc_last
[i
-1-j
];
188 lpc
[i
-1-j
] = b
+ r
* f
;
201 #endif /* AVCODEC_LPC_H */