ref: 590521f8c2da89fa1bd1a4a67bf80e91a008d36d
dir: /nok_ltp_enc.c/
/**************************************************************************
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: 1.5 $
$Date: 2000/02/07 07:45:00 $ (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,
<_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, WS_SIN, 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
References: 1.) buffer2freq
2.) freq2buffer
3.) double_to_int
Explanation: -
Author(s): Juha Ojanpera
*************************************************************************/
void
nok_ltp_reconstruct(double *p_spectrum, 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, j, last_band;
double predicted_samples[2 * NOK_MAX_BLOCK_LEN_LONG];
double overlap_buffer[2 * NOK_MAX_BLOCK_LEN_LONG];
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;
if(lt_status->global_pred_flag)
for (i = 0; i < sfb_offset[last_band]; i++)
p_spectrum[i] += lt_status->pred_mdct[i];
/* Finally update the time domain history buffer. */
freq2buffer (p_spectrum, predicted_samples, overlap_buffer, win_type, WS_SIN, WS_SIN, MNON_OVERLAPPED);
for (i = 0; i < NOK_LT_BLEN - block_size_long; i++)
lt_status->buffer[i] = lt_status->buffer[i + block_size_long];
j = NOK_LT_BLEN - 2 * block_size_long;
for (i = 0; i < block_size_long; i++)
{
lt_status->buffer[i + j] =
double_to_int (predicted_samples[i] + lt_status->buffer[i + j]);
lt_status->buffer[NOK_LT_BLEN - block_size_long + i] =
double_to_int (predicted_samples[i + block_size_long]);
}
break;
case ONLY_SHORT_WINDOW:
#if 0
for (i = 0; i < NOK_LT_BLEN - block_size_long; i++)
lt_status->buffer[i] = lt_status->buffer[i + block_size_long];
for (i = NOK_LT_BLEN - block_size_long; i < NOK_LT_BLEN; i++)
lt_status->buffer[i] = 0;
for (i = 0; i < block_size_long; i++)
overlap_buffer[i] = 0;
/* Finally update the time domain history buffer. */
freq2buffer (p_spectrum, predicted_samples, overlap_buffer, win_type, block_size_long,
block_size_medium, block_size_short, win_shape, MNON_OVERLAPPED);
for(sw = 0; sw < MAX_SHORT_WINDOWS; sw++)
{
i = NOK_LT_BLEN - 2 * block_size_long + SHORT_SQ_OFFSET + sw * block_size_short;
for (j = 0; j < 2 * block_size_short; j++)
lt_status->buffer[i + j] = double_to_int (predicted_samples[sw * block_size_short * 2 + j] +
lt_status->buffer[i + j]);
}
#endif
break;
}
return;
}
/**************************************************************************
Title: nok_ltp_encode
Purpose: Writes LTP parameters to the bit stream.
Usage: nok_ltp_encode (bs, win_type, num_of_sfb, lt_status)
Input: bs - bit stream
win_type - window sequence (frame, block) type
num_of_sfb - number of scalefactor bands
lt_status - side_info:
1, if prediction not used in this frame
>1 otherwise
- weight_idx :
3 bit number indicating the LTP coefficient in
the codebook
- 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
Output: -
References: 1.) BsPutBit
Explanation: -
Author(s): Juha Ojanpera
*************************************************************************/
int
nok_ltp_encode (BsBitStream *bs, enum WINDOW_TYPE win_type, int num_of_sfb,
NOK_LT_PRED_STATUS *lt_status, int write_flag)
{
int i, last_band;
int first_subblock;
int prev_subblock;
int bit_count = 0;
bit_count += 1;
if (lt_status->side_info > 1)
{
if(write_flag)
BsPutBit (bs, 1, 1); /* LTP used */
switch(win_type)
{
case ONLY_LONG_WINDOW:
case LONG_SHORT_WINDOW:
case SHORT_LONG_WINDOW:
bit_count += LEN_LTP_LAG;
bit_count += LEN_LTP_COEF;
if(write_flag)
{
BsPutBit (bs, lt_status->delay[0], LEN_LTP_LAG);
BsPutBit (bs, lt_status->weight_idx, LEN_LTP_COEF);
}
last_band = (num_of_sfb < NOK_MAX_LT_PRED_LONG_SFB) ? num_of_sfb : NOK_MAX_LT_PRED_LONG_SFB;
bit_count += last_band;
if(write_flag)
{
for (i = 0; i < last_band; i++)
BsPutBit (bs, lt_status->sfb_prediction_used[i], LEN_LTP_LONG_USED);
}
break;
case ONLY_SHORT_WINDOW:
for(i=0; i < MAX_SHORT_WINDOWS; i++)
{
if(lt_status->sbk_prediction_used[i])
{
first_subblock = i;
break;
}
}
bit_count += LEN_LTP_LAG;
bit_count += LEN_LTP_COEF;
if(write_flag)
{
BsPutBit (bs, lt_status->delay[first_subblock], LEN_LTP_LAG);
BsPutBit (bs, lt_status->weight_idx, LEN_LTP_COEF);
}
prev_subblock = first_subblock;
for(i = 0; i < MAX_SHORT_WINDOWS; i++)
{
bit_count += LEN_LTP_SHORT_USED;
if(write_flag)
BsPutBit (bs, lt_status->sbk_prediction_used[i], LEN_LTP_SHORT_USED);
if(lt_status->sbk_prediction_used[i])
{
if(i > first_subblock)
{
int diff;
diff = lt_status->delay[prev_subblock] - lt_status->delay[i];
if(diff)
{
bit_count += 1;
bit_count += LEN_LTP_SHORT_LAG;
if(write_flag)
{
BsPutBit (bs, 1, 1);
BsPutBit (bs, diff + NOK_LTP_LAG_OFFSET, LEN_LTP_SHORT_LAG);
}
}
else
{
bit_count += 1;
if(write_flag)
BsPutBit (bs, 0, 1);
}
}
}
}
break;
default:
// CommonExit(1, "nok_ltp_encode : unsupported window sequence %i", win_type);
break;
}
}
else
if(write_flag)
BsPutBit (bs, 0, 1); /* LTP not used */
return (bit_count);
}
/**************************************************************************
Title: double_to_int
Purpose: Converts floating point format to integer (16-bit).
Usage: y = double_to_int(sig_in)
Input: sig_in - floating point number
Output: y - integer number
References: -
Explanation: -
Author(s): Juha Ojanpera
*************************************************************************/
short
double_to_int (double sig_in)
{
short sig_out;
if (sig_in > 32767)
sig_out = 32767;
else if (sig_in < -32768)
sig_out = -32768;
else if (sig_in > 0.0)
sig_out = (short) (sig_in + 0.5);
else if (sig_in <= 0.0)
sig_out = (short) (sig_in - 0.5);
return (sig_out);
}