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ffmpeg / libavcodec / gsmdec_template.c @ 2912e87a

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/*
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 * gsm 06.10 decoder
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 * Copyright (c) 2010 Reimar Döffinger <Reimar.Doeffinger@gmx.de>
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 *
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 * This file is part of Libav.
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 *
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 * Libav is free software; you can redistribute it and/or
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 * modify it under the terms of the GNU Lesser General Public
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 * License as published by the Free Software Foundation; either
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 * version 2.1 of the License, or (at your option) any later version.
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 *
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 * Libav is distributed in the hope that it will be useful,
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 * but WITHOUT ANY WARRANTY; without even the implied warranty of
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 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
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 * Lesser General Public License for more details.
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 *
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 * You should have received a copy of the GNU Lesser General Public
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 * License along with Libav; if not, write to the Free Software
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 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
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 */
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/**
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 * @file
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 * GSM decoder
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 */
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#include "get_bits.h"
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#include "gsmdec_data.h"
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static void apcm_dequant_add(GetBitContext *gb, int16_t *dst)
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{
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    int i;
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    int maxidx = get_bits(gb, 6);
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    const int16_t *tab = ff_gsm_dequant_tab[maxidx];
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    for (i = 0; i < 13; i++)
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        dst[3*i] += tab[get_bits(gb, 3)];
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}
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static inline int gsm_mult(int a, int b)
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{
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    return (a * b + (1 << 14)) >> 15;
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}
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static void long_term_synth(int16_t *dst, int lag, int gain_idx)
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{
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    int i;
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    const int16_t *src = dst - lag;
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    uint16_t gain = ff_gsm_long_term_gain_tab[gain_idx];
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    for (i = 0; i < 40; i++)
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        dst[i] = gsm_mult(gain, src[i]);
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}
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static inline int decode_log_area(int coded, int factor, int offset)
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{
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    coded <<= 10;
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    coded -= offset;
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    return gsm_mult(coded, factor) << 1;
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}
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static av_noinline int get_rrp(int filtered)
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{
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    int abs = FFABS(filtered);
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    if      (abs < 11059) abs <<= 1;
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    else if (abs < 20070) abs += 11059;
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    else                  abs = (abs >> 2) + 26112;
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    return filtered < 0 ? -abs : abs;
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}
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static int filter_value(int in, int rrp[8], int v[9])
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{
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    int i;
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    for (i = 7; i >= 0; i--) {
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        in -= gsm_mult(rrp[i], v[i]);
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        v[i + 1] = v[i] + gsm_mult(rrp[i], in);
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    }
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    v[0] = in;
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    return in;
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}
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static void short_term_synth(GSMContext *ctx, int16_t *dst, const int16_t *src)
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{
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    int i;
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    int rrp[8];
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    int *lar = ctx->lar[ctx->lar_idx];
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    int *lar_prev = ctx->lar[ctx->lar_idx ^ 1];
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    for (i = 0; i < 8; i++)
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        rrp[i] = get_rrp((lar_prev[i] >> 2) + (lar_prev[i] >> 1) + (lar[i] >> 2));
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    for (i = 0; i < 13; i++)
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        dst[i] = filter_value(src[i], rrp, ctx->v);
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    for (i = 0; i < 8; i++)
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        rrp[i] = get_rrp((lar_prev[i] >> 1) + (lar     [i] >> 1));
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    for (i = 13; i < 27; i++)
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        dst[i] = filter_value(src[i], rrp, ctx->v);
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    for (i = 0; i < 8; i++)
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        rrp[i] = get_rrp((lar_prev[i] >> 2) + (lar     [i] >> 1) + (lar[i] >> 2));
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    for (i = 27; i < 40; i++)
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        dst[i] = filter_value(src[i], rrp, ctx->v);
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    for (i = 0; i < 8; i++)
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        rrp[i] = get_rrp(lar[i]);
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    for (i = 40; i < 160; i++)
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        dst[i] = filter_value(src[i], rrp, ctx->v);
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    ctx->lar_idx ^= 1;
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}
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static int postprocess(int16_t *data, int msr)
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{
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    int i;
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    for (i = 0; i < 160; i++) {
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        msr = av_clip_int16(data[i] + gsm_mult(msr, 28180));
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        data[i] = av_clip_int16(msr << 1) & ~7;
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    }
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    return msr;
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}
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static int gsm_decode_block(AVCodecContext *avctx, int16_t *samples,
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                            GetBitContext *gb)
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{
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    GSMContext *ctx = avctx->priv_data;
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    int i;
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    int16_t *ref_dst = ctx->ref_buf + 120;
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    int *lar = ctx->lar[ctx->lar_idx];
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    lar[0] = decode_log_area(get_bits(gb, 6), 13107,  1 << 15);
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    lar[1] = decode_log_area(get_bits(gb, 6), 13107,  1 << 15);
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    lar[2] = decode_log_area(get_bits(gb, 5), 13107, (1 << 14) + 2048*2);
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    lar[3] = decode_log_area(get_bits(gb, 5), 13107, (1 << 14) - 2560*2);
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    lar[4] = decode_log_area(get_bits(gb, 4), 19223, (1 << 13) +   94*2);
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    lar[5] = decode_log_area(get_bits(gb, 4), 17476, (1 << 13) - 1792*2);
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    lar[6] = decode_log_area(get_bits(gb, 3), 31454, (1 << 12) -  341*2);
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    lar[7] = decode_log_area(get_bits(gb, 3), 29708, (1 << 12) - 1144*2);
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    for (i = 0; i < 4; i++) {
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        int lag      = get_bits(gb, 7);
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        int gain_idx = get_bits(gb, 2);
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        int offset   = get_bits(gb, 2);
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        lag = av_clip(lag, 40, 120);
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        long_term_synth(ref_dst, lag, gain_idx);
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        apcm_dequant_add(gb, ref_dst + offset);
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        ref_dst += 40;
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    }
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    memcpy(ctx->ref_buf, ctx->ref_buf + 160, 120 * sizeof(*ctx->ref_buf));
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    short_term_synth(ctx, samples, ctx->ref_buf + 120);
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    // for optimal speed this could be merged with short_term_synth,
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    // not done yet because it is a bit ugly
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    ctx->msr = postprocess(samples, ctx->msr);
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    return 0;
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}