shithub: aacdec

ref: a2a56b3ea59188e2e2b60b69a0a8f77aa3093144
dir: /libfaad/lt_predict.c/

/*
** FAAD - Freeware Advanced Audio Decoder
** Copyright (C) 2002 M. Bakker
**  
** This program is free software; you can redistribute it and/or modify
** it under the terms of the GNU General Public License as published by
** the Free Software Foundation; either version 2 of the License, or
** (at your option) any later version.
** 
** This program 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 General Public License for more details.
** 
** You should have received a copy of the GNU General Public License
** along with this program; if not, write to the Free Software 
** Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
**
** $Id: lt_predict.c,v 1.9 2002/08/27 18:16:12 menno Exp $
**/


#include "common.h"

#ifdef LTP_DEC

#include <stdlib.h>
#include "syntax.h"
#include "lt_predict.h"
#include "filtbank.h"
#include "tns.h"

static real_t codebook[8] =
{
    COEF_CONST(0.570829),
    COEF_CONST(0.696616),
    COEF_CONST(0.813004),
    COEF_CONST(0.911304),
    COEF_CONST(0.984900),
    COEF_CONST(1.067894),
    COEF_CONST(1.194601),
    COEF_CONST(1.369533)
};

void lt_prediction(ic_stream *ics, ltp_info *ltp, real_t *spec,
                   real_t *lt_pred_stat, fb_info *fb, uint8_t win_shape,
                   uint8_t win_shape_prev, uint8_t sr_index,
                   uint8_t object_type, uint16_t frame_len)
{
    uint8_t sfb;
    uint16_t bin, i, num_samples;
    real_t *x_est;
    real_t *X_est;

    if (ics->window_sequence != EIGHT_SHORT_SEQUENCE)
    {
        if (ltp->data_present)
        {
            num_samples = frame_len << 1;

            x_est = (real_t*)malloc(num_samples*sizeof(real_t));
            X_est = (real_t*)malloc(num_samples*sizeof(real_t));

            for(i = 0; i < num_samples; i++)
            {
                /* The extra lookback M (N/2 for LD, 0 for LTP) is handled
                   in the buffer updating */
                x_est[i] = MUL_R_C(lt_pred_stat[num_samples + i - ltp->lag],
                    codebook[ltp->coef]);
            }

            filter_bank_ltp(fb, ics->window_sequence, win_shape, win_shape_prev,
                x_est, X_est, object_type, frame_len);

            tns_encode_frame(ics, &(ics->tns), sr_index, object_type, X_est,
                frame_len);

            for (sfb = 0; sfb < ltp->last_band; sfb++)
            {
                if (ltp->long_used[sfb])
                {
                    uint16_t low  = ics->swb_offset[sfb];
                    uint16_t high = ics->swb_offset[sfb+1];

                    for (bin = low; bin < high; bin++)
                    {
                        spec[bin] += X_est[bin];
                    }
                }
            }

            free(x_est);
            free(X_est);
        }
    }
}

void lt_update_state(real_t *lt_pred_stat, real_t *time, real_t *overlap,
                     uint16_t frame_len, uint8_t object_type)
{
    uint16_t i;

    /*
     * The reference point for index i and the content of the buffer
     * lt_pred_stat are arranged so that lt_pred_stat(0 ... N/2 - 1) contains the
     * last aliased half window from the IMDCT, and lt_pred_stat(N/2 ... N-1)
     * is always all zeros. The rest of lt_pred_stat (i<0) contains the previous
     * fully reconstructed time domain samples, i.e., output of the decoder.
     *
     * These values are shifted up by N*2 to avoid (i<0)
     *
     * For the LD object type an extra 512 samples lookback is accomodated here.
     */
#ifdef LD_DEC
    if (object_type == LD)
    {
        for (i = 0; i < frame_len; i++)
        {
            lt_pred_stat[i]  /* extra 512 */  = lt_pred_stat[i + frame_len];
            lt_pred_stat[frame_len + i]       = lt_pred_stat[i + (frame_len * 2)];
            lt_pred_stat[(frame_len * 2) + i] = time[i];
            lt_pred_stat[(frame_len * 3) + i] = overlap[i];
        }
    } else {
#endif
        for (i = 0; i < frame_len; i++)
        {
            lt_pred_stat[i]                   = lt_pred_stat[i + frame_len];
            lt_pred_stat[frame_len + i]       = time[i];
            lt_pred_stat[(frame_len * 2) + i] = overlap[i];
#if 0 /* set to zero once upon initialisation */
            lt_pred_stat[(frame_len * 3) + i] = 0;
#endif
        }
#ifdef LD_DEC
    }
#endif
}

#endif