2 * various filters for ACELP-based codecs
4 * Copyright (c) 2008 Vladimir Voroshilov
6 * This file is part of FFmpeg.
8 * FFmpeg is free software; you can redistribute it and/or
9 * modify it under the terms of the GNU Lesser General Public
10 * License as published by the Free Software Foundation; either
11 * version 2.1 of the License, or (at your option) any later version.
13 * FFmpeg is distributed in the hope that it will be useful,
14 * but WITHOUT ANY WARRANTY; without even the implied warranty of
15 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
16 * Lesser General Public License for more details.
18 * You should have received a copy of the GNU Lesser General Public
19 * License along with FFmpeg; if not, write to the Free Software
20 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
26 #include "acelp_filters.h"
30 void ff_acelp_convolve_circ(
33 const int16_t* filter,
38 memset(fc_out, 0, subframe_size * sizeof(int16_t));
40 /* Since there are few pulses over an entire subframe (i.e. almost
41 all fc_in[i] are zero) it is faster to swap two loops and process
42 non-zero samples only. In the case of G.729D the buffer contains
43 two non-zero samples before the call to ff_acelp_enhance_harmonics
44 and, due to pitch_delay being bounded by [20; 143], a maximum
45 of four non-zero samples for a total of 40 after the call. */
46 for(i=0; i<subframe_size; i++)
51 fc_out[k] += (fc_in[i] * filter[subframe_size + k - i]) >> 15;
53 for(k=i; k<subframe_size; k++)
54 fc_out[k] += (fc_in[i] * filter[k - i]) >> 15;
59 int ff_acelp_lp_synthesis_filter(
61 const int16_t* filter_coeffs,
69 for(n=0; n<buffer_length; n++)
72 for(i=1; i<filter_length; i++)
73 sum -= filter_coeffs[i] * out[n-i];
75 sum = (sum >> 12) + in[n];
77 /* Check for overflow */
78 if(sum + 0x8000 > 0xFFFFU)
82 sum = (sum >> 31) ^ 32767;
90 void ff_acelp_weighted_filter(
93 const int16_t *weight_pow,
97 for(n=0; n<filter_length; n++)
98 out[n] = (in[n] * weight_pow[n] + 0x4000) >> 15; /* (3.12) = (0.15) * (3.12) with rounding */
101 void ff_acelp_high_pass_filter(
110 for(i=0; i<length; i++)
112 tmp = MULL(hpf_f[0], 15836); /* (14.13) = (13.13) * (1.13) */
113 tmp += MULL(hpf_f[1], -7667); /* (13.13) = (13.13) * (0.13) */
114 tmp += 7699 * (in[i] - 2*in[i-1] + in[i-2]); /* (14.13) = (0.13) * (14.0) */
116 /* Multiplication by 2 with rounding can cause short type
117 overflow, thus clipping is required. */
119 out[i] = av_clip_int16((tmp + 0x800) >> 12); /* (15.0) = 2 * (13.13) = (14.13) */