1/*
2 * gsm 06.10 decoder
3 * Copyright (c) 2010 Reimar Döffinger <Reimar.Doeffinger@gmx.de>
4 *
5 * This file is part of FFmpeg.
6 *
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.
11 *
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.
16 *
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
20 */
21
22/**
23 * @file
24 * GSM decoder
25 */
26
27#include "get_bits.h"
28#include "gsm.h"
29#include "gsmdec_data.h"
30
31static void apcm_dequant_add(GetBitContext *gb, int16_t *dst, const int *frame_bits)
32{
33    int i, val;
34    int maxidx = get_bits(gb, 6);
35    const int16_t *tab = ff_gsm_dequant_tab[maxidx];
36    for (i = 0; i < 13; i++) {
37        val = get_bits(gb, frame_bits[i]);
38        dst[3 * i] += tab[ff_gsm_requant_tab[frame_bits[i]][val]];
39    }
40}
41
42static inline int gsm_mult(int a, int b)
43{
44    return (int)(a * (SUINT)b + (1 << 14)) >> 15;
45}
46
47static void long_term_synth(int16_t *dst, int lag, int gain_idx)
48{
49    int i;
50    const int16_t *src = dst - lag;
51    uint16_t gain = ff_gsm_long_term_gain_tab[gain_idx];
52    for (i = 0; i < 40; i++)
53        dst[i] = gsm_mult(gain, src[i]);
54}
55
56static inline int decode_log_area(int coded, int factor, int offset)
57{
58    coded <<= 10;
59    coded -= offset;
60    return gsm_mult(coded, factor) * 2;
61}
62
63static av_noinline int get_rrp(int filtered)
64{
65    int abs = FFABS(filtered);
66    if      (abs < 11059) abs <<= 1;
67    else if (abs < 20070) abs += 11059;
68    else                  abs = (abs >> 2) + 26112;
69    return filtered < 0 ? -abs : abs;
70}
71
72static int filter_value(int in, int rrp[8], int v[9])
73{
74    int i;
75    for (i = 7; i >= 0; i--) {
76        in -= gsm_mult(rrp[i], v[i]);
77        v[i + 1] = v[i] + gsm_mult(rrp[i], in);
78    }
79    v[0] = in;
80    return in;
81}
82
83static void short_term_synth(GSMContext *ctx, int16_t *dst, const int16_t *src)
84{
85    int i;
86    int rrp[8];
87    int *lar = ctx->lar[ctx->lar_idx];
88    int *lar_prev = ctx->lar[ctx->lar_idx ^ 1];
89    for (i = 0; i < 8; i++)
90        rrp[i] = get_rrp((lar_prev[i] >> 2) + (lar_prev[i] >> 1) + (lar[i] >> 2));
91    for (i = 0; i < 13; i++)
92        dst[i] = filter_value(src[i], rrp, ctx->v);
93
94    for (i = 0; i < 8; i++)
95        rrp[i] = get_rrp((lar_prev[i] >> 1) + (lar     [i] >> 1));
96    for (i = 13; i < 27; i++)
97        dst[i] = filter_value(src[i], rrp, ctx->v);
98
99    for (i = 0; i < 8; i++)
100        rrp[i] = get_rrp((lar_prev[i] >> 2) + (lar     [i] >> 1) + (lar[i] >> 2));
101    for (i = 27; i < 40; i++)
102        dst[i] = filter_value(src[i], rrp, ctx->v);
103
104    for (i = 0; i < 8; i++)
105        rrp[i] = get_rrp(lar[i]);
106    for (i = 40; i < 160; i++)
107        dst[i] = filter_value(src[i], rrp, ctx->v);
108
109    ctx->lar_idx ^= 1;
110}
111
112static int postprocess(int16_t *data, int msr)
113{
114    int i;
115    for (i = 0; i < 160; i++) {
116        msr = av_clip_int16(data[i] + gsm_mult(msr, 28180));
117        data[i] = av_clip_int16(msr * 2) & ~7;
118    }
119    return msr;
120}
121
122static int gsm_decode_block(AVCodecContext *avctx, int16_t *samples,
123                            GetBitContext *gb, int mode)
124{
125    GSMContext *ctx = avctx->priv_data;
126    int i;
127    int16_t *ref_dst = ctx->ref_buf + 120;
128    int *lar = ctx->lar[ctx->lar_idx];
129    lar[0] = decode_log_area(get_bits(gb, 6), 13107,  1 << 15);
130    lar[1] = decode_log_area(get_bits(gb, 6), 13107,  1 << 15);
131    lar[2] = decode_log_area(get_bits(gb, 5), 13107, (1 << 14) + 2048*2);
132    lar[3] = decode_log_area(get_bits(gb, 5), 13107, (1 << 14) - 2560*2);
133    lar[4] = decode_log_area(get_bits(gb, 4), 19223, (1 << 13) +   94*2);
134    lar[5] = decode_log_area(get_bits(gb, 4), 17476, (1 << 13) - 1792*2);
135    lar[6] = decode_log_area(get_bits(gb, 3), 31454, (1 << 12) -  341*2);
136    lar[7] = decode_log_area(get_bits(gb, 3), 29708, (1 << 12) - 1144*2);
137
138    for (i = 0; i < 4; i++) {
139        int lag      = get_bits(gb, 7);
140        int gain_idx = get_bits(gb, 2);
141        int offset   = get_bits(gb, 2);
142        lag = av_clip(lag, 40, 120);
143        long_term_synth(ref_dst, lag, gain_idx);
144        apcm_dequant_add(gb, ref_dst + offset, ff_gsm_apcm_bits[mode][i]);
145        ref_dst += 40;
146    }
147    memcpy(ctx->ref_buf, ctx->ref_buf + 160, 120 * sizeof(*ctx->ref_buf));
148    short_term_synth(ctx, samples, ctx->ref_buf + 120);
149    // for optimal speed this could be merged with short_term_synth,
150    // not done yet because it is a bit ugly
151    ctx->msr = postprocess(samples, ctx->msr);
152    return 0;
153}
154