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libavcodec/gsmdec_template.c

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00001 /*
00002  * gsm 06.10 decoder
00003  * Copyright (c) 2010 Reimar Döffinger <Reimar.Doeffinger@gmx.de>
00004  *
00005  * This file is part of FFmpeg.
00006  *
00007  * FFmpeg is free software; you can redistribute it and/or
00008  * modify it under the terms of the GNU Lesser General Public
00009  * License as published by the Free Software Foundation; either
00010  * version 2.1 of the License, or (at your option) any later version.
00011  *
00012  * FFmpeg is distributed in the hope that it will be useful,
00013  * but WITHOUT ANY WARRANTY; without even the implied warranty of
00014  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
00015  * Lesser General Public License for more details.
00016  *
00017  * You should have received a copy of the GNU Lesser General Public
00018  * License along with FFmpeg; if not, write to the Free Software
00019  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
00020  */
00021 
00027 #include "get_bits.h"
00028 #include "gsmdec_data.h"
00029 
00030 static void apcm_dequant_add(GetBitContext *gb, int16_t *dst)
00031 {
00032     int i;
00033     int maxidx = get_bits(gb, 6);
00034     const int16_t *tab = ff_gsm_dequant_tab[maxidx];
00035     for (i = 0; i < 13; i++)
00036         dst[3*i] += tab[get_bits(gb, 3)];
00037 }
00038 
00039 static inline int gsm_mult(int a, int b)
00040 {
00041     return (a * b + (1 << 14)) >> 15;
00042 }
00043 
00044 static void long_term_synth(int16_t *dst, int lag, int gain_idx)
00045 {
00046     int i;
00047     const int16_t *src = dst - lag;
00048     uint16_t gain = ff_gsm_long_term_gain_tab[gain_idx];
00049     for (i = 0; i < 40; i++)
00050         dst[i] = gsm_mult(gain, src[i]);
00051 }
00052 
00053 static inline int decode_log_area(int coded, int factor, int offset)
00054 {
00055     coded <<= 10;
00056     coded -= offset;
00057     return gsm_mult(coded, factor) << 1;
00058 }
00059 
00060 static av_noinline int get_rrp(int filtered)
00061 {
00062     int abs = FFABS(filtered);
00063     if      (abs < 11059) abs <<= 1;
00064     else if (abs < 20070) abs += 11059;
00065     else                  abs = (abs >> 2) + 26112;
00066     return filtered < 0 ? -abs : abs;
00067 }
00068 
00069 static int filter_value(int in, int rrp[8], int v[9])
00070 {
00071     int i;
00072     for (i = 7; i >= 0; i--) {
00073         in -= gsm_mult(rrp[i], v[i]);
00074         v[i + 1] = v[i] + gsm_mult(rrp[i], in);
00075     }
00076     v[0] = in;
00077     return in;
00078 }
00079 
00080 static void short_term_synth(GSMContext *ctx, int16_t *dst, const int16_t *src)
00081 {
00082     int i;
00083     int rrp[8];
00084     int *lar = ctx->lar[ctx->lar_idx];
00085     int *lar_prev = ctx->lar[ctx->lar_idx ^ 1];
00086     for (i = 0; i < 8; i++)
00087         rrp[i] = get_rrp((lar_prev[i] >> 2) + (lar_prev[i] >> 1) + (lar[i] >> 2));
00088     for (i = 0; i < 13; i++)
00089         dst[i] = filter_value(src[i], rrp, ctx->v);
00090 
00091     for (i = 0; i < 8; i++)
00092         rrp[i] = get_rrp((lar_prev[i] >> 1) + (lar     [i] >> 1));
00093     for (i = 13; i < 27; i++)
00094         dst[i] = filter_value(src[i], rrp, ctx->v);
00095 
00096     for (i = 0; i < 8; i++)
00097         rrp[i] = get_rrp((lar_prev[i] >> 2) + (lar     [i] >> 1) + (lar[i] >> 2));
00098     for (i = 27; i < 40; i++)
00099         dst[i] = filter_value(src[i], rrp, ctx->v);
00100 
00101     for (i = 0; i < 8; i++)
00102         rrp[i] = get_rrp(lar[i]);
00103     for (i = 40; i < 160; i++)
00104         dst[i] = filter_value(src[i], rrp, ctx->v);
00105 
00106     ctx->lar_idx ^= 1;
00107 }
00108 
00109 static int postprocess(int16_t *data, int msr)
00110 {
00111     int i;
00112     for (i = 0; i < 160; i++) {
00113         msr = av_clip_int16(data[i] + gsm_mult(msr, 28180));
00114         data[i] = av_clip_int16(msr << 1) & ~7;
00115     }
00116     return msr;
00117 }
00118 
00119 static int gsm_decode_block(AVCodecContext *avctx, int16_t *samples,
00120                             GetBitContext *gb)
00121 {
00122     GSMContext *ctx = avctx->priv_data;
00123     int i;
00124     int16_t *ref_dst = ctx->ref_buf + 120;
00125     int *lar = ctx->lar[ctx->lar_idx];
00126     lar[0] = decode_log_area(get_bits(gb, 6), 13107,  1 << 15);
00127     lar[1] = decode_log_area(get_bits(gb, 6), 13107,  1 << 15);
00128     lar[2] = decode_log_area(get_bits(gb, 5), 13107, (1 << 14) + 2048*2);
00129     lar[3] = decode_log_area(get_bits(gb, 5), 13107, (1 << 14) - 2560*2);
00130     lar[4] = decode_log_area(get_bits(gb, 4), 19223, (1 << 13) +   94*2);
00131     lar[5] = decode_log_area(get_bits(gb, 4), 17476, (1 << 13) - 1792*2);
00132     lar[6] = decode_log_area(get_bits(gb, 3), 31454, (1 << 12) -  341*2);
00133     lar[7] = decode_log_area(get_bits(gb, 3), 29708, (1 << 12) - 1144*2);
00134 
00135     for (i = 0; i < 4; i++) {
00136         int lag      = get_bits(gb, 7);
00137         int gain_idx = get_bits(gb, 2);
00138         int offset   = get_bits(gb, 2);
00139         lag = av_clip(lag, 40, 120);
00140         long_term_synth(ref_dst, lag, gain_idx);
00141         apcm_dequant_add(gb, ref_dst + offset);
00142         ref_dst += 40;
00143     }
00144     memcpy(ctx->ref_buf, ctx->ref_buf + 160, 120 * sizeof(*ctx->ref_buf));
00145     short_term_synth(ctx, samples, ctx->ref_buf + 120);
00146     // for optimal speed this could be merged with short_term_synth,
00147     // not done yet because it is a bit ugly
00148     ctx->msr = postprocess(samples, ctx->msr);
00149     return 0;
00150 }

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