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