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"
28 const int16_t ff_acelp_interp_filter[61] =
30 29443, 28346, 25207, 20449, 14701, 8693,
31 3143, -1352, -4402, -5865, -5850, -4673,
32 -2783, -672, 1211, 2536, 3130, 2991,
33 2259, 1170, 0, -1001, -1652, -1868,
34 -1666, -1147, -464, 218, 756, 1060,
35 1099, 904, 550, 135, -245, -514,
36 -634, -602, -451, -231, 0, 191,
37 308, 340, 296, 198, 78, -36,
38 -120, -163, -165, -132, -79, -19,
39 34, 73, 91, 89, 70, 38,
43 void ff_acelp_interpolate(
46 const int16_t* filter_coeffs,
54 assert(pitch_delay_frac >= 0 && pitch_delay_frac < precision);
56 for(n=0; n<length; n++)
61 for(i=0; i<filter_length;)
64 /* The reference G.729 and AMR fixed point code performs clipping after
65 each of the two following accumulations.
66 Since clipping affects only the synthetic OVERFLOW test without
67 causing an int type overflow, it was moved outside the loop. */
70 v += R(n-i)*ff_acelp_interp_filter(t+6i)
71 v += R(n+i+1)*ff_acelp_interp_filter(6-t+6i) */
73 v += in[n + i] * filter_coeffs[idx + frac_pos];
76 v += in[n - i] * filter_coeffs[idx - frac_pos];
78 if(av_clip_int16(v>>15) != (v>>15))
79 av_log(NULL, AV_LOG_WARNING, "overflow that would need cliping in ff_acelp_interpolate()\n");
85 void ff_acelp_high_pass_filter(
94 for(i=0; i<length; i++)
96 tmp = (hpf_f[0]* 15836LL)>>13;
97 tmp += (hpf_f[1]* -7667LL)>>13;
98 tmp += 7699 * (in[i] - 2*in[i-1] + in[i-2]);
100 /* With "+0x800" rounding, clipping is needed
101 for ALGTHM and SPEECH tests. */
102 out[i] = av_clip_int16((tmp + 0x800) >> 12);