nok_ltp_enc.c

AAC音频解码算法程序

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

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.  

***************************************************************************/
/**************************************************************************
  nok_ltp_enc.c  -  Performs Long Term Prediction for the MPEG-4 
                    T/F Encoder.
  Author(s): Mikko Suonio, Juha Ojanpera
  	     Nokia Research Center, Speech and Audio Systems, 1997.
  *************************************************************************/


/**************************************************************************
  Version Control Information			Method: CVS
  Identifiers:
  $Revision: 1.3 $
  $Date: 2000/01/08 13:31:28 $ (check in)
  $Author: lenox $
  *************************************************************************/


/**************************************************************************
  External Objects Needed
  *************************************************************************/
/*
  Standard library declarations.  */
#include <stdio.h>

/*
  Interface to related modules.  */
#include "tf_main.h"
#include "interface.h"
#include "bitstream.h"
#include "nok_ltp_common.h"
#include "nok_pitch.h"

/**************************************************************************
  External Objects Provided
  *************************************************************************/
#include "nok_ltp_enc.h"

/**************************************************************************
  Internal Objects
  *************************************************************************/
#include "nok_ltp_common_internal.h"

short double_to_int (double sig_in);


/**************************************************************************
  Title:	nok_init_lt_pred

  Purpose:	Initialize the history buffer for long term prediction

  Usage:        nok_init_lt_pred (lt_status)

  Input:	lt_status
  			- buffer: history buffer
                        - pred_mdct: prediction transformed to frequency 
                          domain
                        - weight_idx : 
                          3 bit number indicating the LTP coefficient in 
                          the codebook 
                        - sbk_prediction_used: 
                          1 bit for each subblock indicating wheather
                          LTP is used in that subblock 
                        - sfb_prediction_used:
                          1 bit for each scalefactor band (sfb) where LTP 
                          can be used indicating whether LTP is switched 
                          on (1) /off (0) in that sfb.
                        - delay: LTP lag
                        - side_info: LTP side information

  Output:	lt_status
  			- buffer: filled with 0
                        - pred_mdct: filled with 0
                        - weight_idx : filled with 0
                        - sbk_prediction_used: filled with 0
                        - sfb_prediction_used: filled with 0
                        - delay: filled with 0
                        - side_info: filled with 1

  References:	-

  Explanation:	-

  Author(s):	Mikko Suonio
  *************************************************************************/
void
nok_init_lt_pred (NOK_LT_PRED_STATUS *lt_status)
{
	int i;

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

	for (i = 0; i < NOK_MAX_BLOCK_LEN_LONG; i++)
		lt_status->pred_mdct[i] = 0;

	lt_status->weight_idx = 0;
	for(i=0; i<NSHORT; i++)
		lt_status->sbk_prediction_used[i] = lt_status->delay[i] = 0;

	for(i=0; i<MAX_SCFAC_BANDS; i++)
		lt_status->sfb_prediction_used[i] = 0;

	lt_status->side_info = LEN_LTP_DATA_PRESENT;
}


/**************************************************************************
  Title:	nok_ltp_enc

  Purpose:      Performs long term prediction.

  Usage:	nok_ltp_enc(p_spectrum, p_time_signal, win_type, win_shape, 
                            sfb_offset, num_of_sfb, lt_status, buffer_update)

  Input:        p_spectrum    - spectral coefficients
                p_time_signal - time domain input samples
                win_type      - window sequence (frame, block) type
                win_shape     - shape of the mdct window
                sfb_offset    - scalefactor band boundaries
                num_of_sfb    - number of scalefactor bands in each block

  Output:	p_spectrum    - residual spectrum
                lt_status     - buffer: history buffer
                              - pred_mdct:prediction transformed to frequency domain
                                for subsequent use
                              - weight_idx : 
                                3 bit number indicating the LTP coefficient in 
                                the codebook 
                              - sbk_prediction_used: 
                                1 bit for each subblock indicating wheather
                                LTP is used in that subblock 
                              - sfb_prediction_used:
                                1 bit for each scalefactor band (sfb) where LTP 
                                can be used indicating whether LTP is switched 
                                on (1) /off (0) in that sfb.
                              - delay: LTP lag
                              - side_info: LTP side information
                        
  References:	1.) estimate_delay in nok_pitch.c
                2.) pitch in nok_pitch.c
                3.) buffer2freq
                4.) snr_pred in nok_pitch.c
                5.) freq2buffer
                6.) double_to_int

  Explanation:  -

  Author(s):	Juha Ojanpera
  *************************************************************************/

int nok_ltp_enc(double *p_spectrum, double *p_time_signal, enum WINDOW_TYPE win_type, 
            Window_shape win_shape, int block_size_long, int block_size_medium,
	    int block_size_short, int *sfb_offset, int num_of_sfb,
            NOK_LT_PRED_STATUS *lt_status)
{
    int i;
    int last_band;
	double num_bit[MAX_SHORT_WINDOWS];
    double predicted_samples[2 * NOK_MAX_BLOCK_LEN_LONG];

    lt_status->global_pred_flag = 0;
    lt_status->side_info = 1;

    switch(win_type)
    {
	case ONLY_LONG_WINDOW:
	case LONG_SHORT_WINDOW:
	case SHORT_LONG_WINDOW:
		last_band = (num_of_sfb < NOK_MAX_LT_PRED_LONG_SFB) ? num_of_sfb : NOK_MAX_LT_PRED_LONG_SFB;

		lt_status->delay[0] = estimate_delay (p_time_signal, lt_status->buffer, 2 * block_size_long);

//		fprintf(stderr, "(LTP) lag : %i ", lt_status->delay[0]);

		pitch (p_time_signal, predicted_samples, lt_status->buffer, 
			&lt_status->weight_idx, lt_status->delay[0], 2 * block_size_long);

		/* Transform prediction to frequency domain and save it for subsequent use. */
		buffer2freq (predicted_samples, lt_status->pred_mdct, NULL, win_type,
			win_shape, block_size_long, block_size_medium,
			block_size_short, MNON_OVERLAPPED);

		lt_status->side_info = LEN_LTP_DATA_PRESENT + last_band + LEN_LTP_LAG + LEN_LTP_COEF;
    
		num_bit[0] = snr_pred (p_spectrum, lt_status->pred_mdct,
			lt_status->sfb_prediction_used, sfb_offset, 
			win_type, lt_status->side_info, last_band);

//		if (num_bit[0] > 0) {
//			fprintf(stderr, "(LTP) lag : %i ", lt_status->delay[0]);
//			fprintf(stderr, " bit gain : %f\n", num_bit[0]);
//		}

		lt_status->global_pred_flag = (num_bit[0] == 0.0) ? 0 : 1;

		if(lt_status->global_pred_flag)
			for (i = 0; i < sfb_offset[last_band]; i++)
				p_spectrum[i] -= lt_status->pred_mdct[i];
		else
			lt_status->side_info = 1;
        break;

	case ONLY_SHORT_WINDOW:
		break;
    }
    
    return (lt_status->global_pred_flag);
}


/**************************************************************************
  Title:	nok_ltp_reconstruct

  Purpose:      Updates LTP history buffer.

  Usage:	nok_ltp_reconstruct(p_spectrum, win_type,  win_shape, 
                                    block_size_long, block_size_medium,
                                    block_size_short, sfb_offset, 
                                    num_of_sfb, lt_status)

  Input:        p_spectrum    - reconstructed spectrum
                win_type      - window sequence (frame, block) type
                win_shape     - shape of the mdct window
                sfb_offset    - scalefactor band boundaries
                num_of_sfb    - number of scalefactor bands in each block

  Output:	p_spectrum    - reconstructed spectrum
                lt_status     - buffer: history buffer