/*
  * gsm 06.10 decoder
  * Copyright (c) 2010 Reimar Döffinger <Reimar.Doeffinger@gmx.de>
  *
  * This file is part of FFmpeg.
  *
  * FFmpeg is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Lesser General Public
  * License as published by the Free Software Foundation; either
  * version 2.1 of the License, or (at your option) any later version.
  *
  * FFmpeg is distributed in the hope that it will be useful,
  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  * Lesser General Public License for more details.
  *
  * You should have received a copy of the GNU Lesser General Public
  * License along with FFmpeg; if not, write to the Free Software
  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
  */
 
 /**
  * @file
  * GSM decoder
  */
 
 #include "get_bits.h"

 #include "gsm.h"

 #include "gsmdec_data.h"
 

 static const int requant_tab[4][8] = {
     { 0 },
     { 0, 7 },
     { 0, 2, 5, 7 },
     { 0, 1, 2, 3, 4, 5, 6, 7 }
 };
 
 static void apcm_dequant_add(GetBitContext *gb, int16_t *dst, const int *frame_bits)

 {

     int i, val;

     int maxidx = get_bits(gb, 6);
     const int16_t *tab = ff_gsm_dequant_tab[maxidx];

     for (i = 0; i < 13; i++) {
         val = get_bits(gb, frame_bits[i]);
         dst[3*i] += tab[requant_tab[frame_bits[i]][val]];
     }

 }
 
 static inline int gsm_mult(int a, int b)
 {
     return (a * b + (1 << 14)) >> 15;
 }
 
 static void long_term_synth(int16_t *dst, int lag, int gain_idx)
 {
     int i;
     const int16_t *src = dst - lag;
     uint16_t gain = ff_gsm_long_term_gain_tab[gain_idx];
     for (i = 0; i < 40; i++)
         dst[i] = gsm_mult(gain, src[i]);
 }
 
 static inline int decode_log_area(int coded, int factor, int offset)
 {
     coded <<= 10;
     coded -= offset;
     return gsm_mult(coded, factor) << 1;
 }
 
 static av_noinline int get_rrp(int filtered)
 {
     int abs = FFABS(filtered);
     if      (abs < 11059) abs <<= 1;
     else if (abs < 20070) abs += 11059;
     else                  abs = (abs >> 2) + 26112;
     return filtered < 0 ? -abs : abs;
 }
 
 static int filter_value(int in, int rrp[8], int v[9])
 {
     int i;
     for (i = 7; i >= 0; i--) {
         in -= gsm_mult(rrp[i], v[i]);
         v[i + 1] = v[i] + gsm_mult(rrp[i], in);
     }
     v[0] = in;
     return in;
 }
 
 static void short_term_synth(GSMContext *ctx, int16_t *dst, const int16_t *src)
 {
     int i;
     int rrp[8];
     int *lar = ctx->lar[ctx->lar_idx];
     int *lar_prev = ctx->lar[ctx->lar_idx ^ 1];
     for (i = 0; i < 8; i++)
         rrp[i] = get_rrp((lar_prev[i] >> 2) + (lar_prev[i] >> 1) + (lar[i] >> 2));
     for (i = 0; i < 13; i++)
         dst[i] = filter_value(src[i], rrp, ctx->v);
 
     for (i = 0; i < 8; i++)
         rrp[i] = get_rrp((lar_prev[i] >> 1) + (lar     [i] >> 1));
     for (i = 13; i < 27; i++)
         dst[i] = filter_value(src[i], rrp, ctx->v);
 
     for (i = 0; i < 8; i++)
         rrp[i] = get_rrp((lar_prev[i] >> 2) + (lar     [i] >> 1) + (lar[i] >> 2));
     for (i = 27; i < 40; i++)
         dst[i] = filter_value(src[i], rrp, ctx->v);
 
     for (i = 0; i < 8; i++)
         rrp[i] = get_rrp(lar[i]);
     for (i = 40; i < 160; i++)
         dst[i] = filter_value(src[i], rrp, ctx->v);
 
     ctx->lar_idx ^= 1;
 }
 
 static int postprocess(int16_t *data, int msr)
 {
     int i;
     for (i = 0; i < 160; i++) {
         msr = av_clip_int16(data[i] + gsm_mult(msr, 28180));
         data[i] = av_clip_int16(msr << 1) & ~7;
     }
     return msr;
 }
 
 static int gsm_decode_block(AVCodecContext *avctx, int16_t *samples,

                             GetBitContext *gb, int mode)

 {
     GSMContext *ctx = avctx->priv_data;
     int i;
     int16_t *ref_dst = ctx->ref_buf + 120;
     int *lar = ctx->lar[ctx->lar_idx];
     lar[0] = decode_log_area(get_bits(gb, 6), 13107,  1 << 15);
     lar[1] = decode_log_area(get_bits(gb, 6), 13107,  1 << 15);
     lar[2] = decode_log_area(get_bits(gb, 5), 13107, (1 << 14) + 2048*2);
     lar[3] = decode_log_area(get_bits(gb, 5), 13107, (1 << 14) - 2560*2);
     lar[4] = decode_log_area(get_bits(gb, 4), 19223, (1 << 13) +   94*2);
     lar[5] = decode_log_area(get_bits(gb, 4), 17476, (1 << 13) - 1792*2);
     lar[6] = decode_log_area(get_bits(gb, 3), 31454, (1 << 12) -  341*2);
     lar[7] = decode_log_area(get_bits(gb, 3), 29708, (1 << 12) - 1144*2);
 
     for (i = 0; i < 4; i++) {
         int lag      = get_bits(gb, 7);
         int gain_idx = get_bits(gb, 2);
         int offset   = get_bits(gb, 2);
         lag = av_clip(lag, 40, 120);
         long_term_synth(ref_dst, lag, gain_idx);

         apcm_dequant_add(gb, ref_dst + offset, ff_gsm_apcm_bits[mode][i]);

         ref_dst += 40;
     }
     memcpy(ctx->ref_buf, ctx->ref_buf + 160, 120 * sizeof(*ctx->ref_buf));
     short_term_synth(ctx, samples, ctx->ref_buf + 120);
     // for optimal speed this could be merged with short_term_synth,
     // not done yet because it is a bit ugly
     ctx->msr = postprocess(samples, ctx->msr);
     return 0;
 }