nok_lt_prediction.c

网络MPEG4IP流媒体开发源代码

/**************************************************************************

This software module was originally developed by
Nokia in the course of development of the MPEG-2 AAC/MPEG-4
Audio standard ISO/IEC13818-7, 14496-1, 2 and 3.
This software module is an implementation of a part
of one or more MPEG-2 AAC/MPEG-4 Audio tools as specified by the
MPEG-2 aac/MPEG-4 Audio standard. ISO/IEC  gives users of the
MPEG-2aac/MPEG-4 Audio standards free license to this software module
or modifications thereof for use in hardware or software products
claiming conformance to the MPEG-2 aac/MPEG-4 Audio  standards. Those
intending to use this software module in hardware or software products
are advised that this use may infringe existing patents. The original
developer of this software module, the subsequent
editors and their companies, and ISO/IEC have no liability for use of
this software module or modifications thereof in an
implementation. Copyright is not released for non MPEG-2 aac/MPEG-4
Audio conforming products. The original developer retains full right to
use the code for the developer's own purpose, assign or donate the code to a
third party and to inhibit third party from using the code for non
MPEG-2 aac/MPEG-4 Audio conforming products. This copyright notice
must be included in all copies or derivative works.
Copyright (c)1997.

***************************************************************************/
/*
 * $Id$
 */

#include "all.h"
#include "tns.h"
#include "block.h"
#include "nok_ltp_common.h"
#include "nok_lt_prediction.h"
#include "nok_ltp_common_internal.h"
#include "port.h"
#include "bits.h"
#include "util.h"

/*
  Initialize the history buffer for long term prediction
 */

void nok_init_lt_pred(NOK_LT_PRED_STATUS **lt_status, int channels)
{
    int ch;

    for (ch = 0; ch < channels; ch++) {
        lt_status[ch]->buffer = AllocMemory(NOK_LT_BLEN*sizeof(float));
#ifndef _WIN32
        SetMemory(lt_status[ch]->buffer, 0, NOK_LT_BLEN*sizeof(float));
#endif
    }
}

void nok_end_lt_pred(NOK_LT_PRED_STATUS **lt_status, int channels)
{
    int ch;

    for (ch = 0; ch < channels; ch++) {
        if (lt_status[ch]->buffer) FreeMemory(lt_status[ch]->buffer);
    }
}


/**************************************************************************
  nok_lt_prediction
 *************************************************************************/

void nok_lt_predict(faacDecHandle hDecoder, Info *info, WINDOW_TYPE win_type, Wnd_Shape *win_shape,
                    int *sbk_prediction_used, int *sfb_prediction_used,
                    NOK_LT_PRED_STATUS *lt_status, Float weight, int *delay,
                    Float *current_frame, int block_size_long, int block_size_medium,
                    int block_size_short, TNS_frame_info *tns_frame_info)
{
    int i, j, num_samples;
    float_ext *mdct_predicted;
    float_ext *predicted_samples;

    mdct_predicted = AllocMemory(2*NOK_MAX_BLOCK_LEN_LONG*sizeof(float_ext));
    predicted_samples = AllocMemory(2*NOK_MAX_BLOCK_LEN_LONG*sizeof(float_ext));


    switch(win_type) {

    case ONLY_LONG_WINDOW:
    case LONG_START_WINDOW:
    case LONG_STOP_WINDOW:
        if (sbk_prediction_used[0])
        {
            /* Prediction for time domain signal */
            num_samples =  2 * block_size_long;
            j = NOK_LT_BLEN - 2 * block_size_long - (delay[0] - MAX_LTP_DELAY / 2);
            if(NOK_LT_BLEN - j <  2 * block_size_long)
                num_samples = NOK_LT_BLEN - j;

            for(i = 0; i < num_samples; i++)
                predicted_samples[i] = weight * lt_status->buffer[i + j];
            for( ; i < 2 * block_size_long; i++)
                predicted_samples[i] = 0.0f;

            /* Transform prediction to frequency domain. */
            time2freq_adapt(hDecoder, win_type, win_shape, predicted_samples, mdct_predicted);

            /* Apply the TNS analysis filter to the predicted spectrum. */
            if(tns_frame_info != NULL)
                tns_filter_subblock(hDecoder, mdct_predicted, info->sfb_per_bk, info->sbk_sfb_top[0],
                1, &tns_frame_info->info[0]);

            /* Clean those sfb's where prediction is not used. */
            for (i = 0, j = 0; i < info->sfb_per_bk; i++) {
                if (sfb_prediction_used[i + 1] == 0) {
                    for (; j < info->sbk_sfb_top[0][i]; j++)
                        mdct_predicted[j] = 0.0;
                } else {
                    j = info->sbk_sfb_top[0][i];
                }
            }

            /* Add the prediction to dequantized spectrum. */
            for (i = 0; i < block_size_long; i++)
                current_frame[i] = current_frame[i] + mdct_predicted[i];
        }
        break;

    default:
        break;
    }

    FreeMemory(mdct_predicted);
    FreeMemory(predicted_samples);
}

/**************************************************************************
  nok_lt_update
 *************************************************************************/

void nok_lt_update(NOK_LT_PRED_STATUS *lt_status, Float *time_signal,
                   Float *overlap_signal, int block_size_long)
{
    int i;

    for(i = 0; i < NOK_LT_BLEN - 2 * block_size_long; i++)
        lt_status->buffer[i] = lt_status->buffer[i + block_size_long];

    for(i = 0; i < block_size_long; i++)
    {
        lt_status->buffer[NOK_LT_BLEN - 2 * block_size_long + i] =
            time_signal[i];

        lt_status->buffer[NOK_LT_BLEN - block_size_long + i] =
            overlap_signal[i];
    }
}

/**************************************************************************
  nok_lt_decode
 *************************************************************************/
void nok_lt_decode(faacDecHandle hDecoder, int max_sfb, int *sbk_prediction_used,
                   int *sfb_prediction_used, Float *weight, int *delay)
{
    int i, last_band;

    if ((sbk_prediction_used[0] = faad_getbits(&hDecoder->ld, LEN_LTP_DATA_PRESENT)))
    {
        delay[0] = faad_getbits(&hDecoder->ld, 11);
        *weight = codebook[faad_getbits(&hDecoder->ld, 3)];

        last_band = (max_sfb < NOK_MAX_LT_PRED_LONG_SFB
            ? max_sfb : NOK_MAX_LT_PRED_LONG_SFB) + 1;

        sfb_prediction_used[0] = sbk_prediction_used[0];
        for (i = 1; i < last_band; i++)
            sfb_prediction_used[i] = faad_getbits(&hDecoder->ld, LEN_LTP_LONG_USED);
        for (; i < max_sfb + 1; i++)
            sfb_prediction_used[i] = 0;
    }
}