melp_chn.c

2400bps MELP语音编解码源程序。

/*

2.4 kbps MELP Proposed Federal Standard speech coder

Fixed-point C code, version 1.0

Copyright (c) 1998, Texas Instruments, Inc.  

Texas Instruments has intellectual property rights on the MELP
algorithm.  The Texas Instruments contact for licensing issues for
commercial and non-government use is William Gordon, Director,
Government Contracts, Texas Instruments Incorporated, Semiconductor
Group (phone [phone]).

The fixed-point version of the voice codec Mixed Excitation Linear
Prediction (MELP) is based on specifications on the C-language software
simulation contained in GSM 06.06 which is protected by copyright and
is the property of the European Telecommunications Standards Institute
(ETSI). This standard is available from the ETSI publication office
tel. [phone]. ETSI has granted a license to United States
Department of Defense to use the C-language software simulation contained
in GSM 06.06 for the purposes of the development of a fixed-point
version of the voice codec Mixed Excitation Linear Prediction (MELP).
Requests for authorization to make other use of the GSM 06.06 or
otherwise distribute or modify them need to be addressed to the ETSI
Secretariat fax: [phone].

*/
/*
    Name: melp_chn_write, melp_chn_read
    Description: Write/read MELP channel bitstream
    Inputs:
      MELP parameter structure
    Outputs: 
      updated MELP parameter structure (channel pointers)
    Returns: void
*/

#include <stdio.h>
#include <math.h>
#include "typedefs.h"
#include "melp.h"
#include "vq.h"
#include "melp_sub.h"
#include "math_lib.h"
#include "constant.h"

/* Define number of channel bits per frame */
#define NUM_CH_BITS 54
#define ORIGINAL_BIT_ORDER 0  /* flag to use bit order of original version */

extern Shortword msvq_cb[];
extern Shortword msvq_cb_mean[];
extern Shortword fsvq_cb[];

/* Define bit buffer */
static UShortword bit_buffer[NUM_CH_BITS];

#if (ORIGINAL_BIT_ORDER)
/* Original linear order */
static Shortword bit_order[NUM_CH_BITS] = {
0,  1,  2,  3,  4,  5,
6,  7,  8,  9,  10, 11,
12, 13, 14, 15, 16, 17, 
18, 19, 20, 21, 22, 23,
24, 25, 26, 27, 28, 29,
30, 31, 32, 33, 34, 35,
36, 37, 38, 39, 40, 41, 
42, 43, 44, 45, 46, 47, 
48, 49, 50, 51, 52, 53};
#else
/* Order based on priority of bits */
static Shortword bit_order[NUM_CH_BITS] = {
0,  17, 9,  28, 34, 3, 
4,  39, 1,  2,  13, 38,
14, 10, 11, 40, 15, 21,
27, 45, 12, 26, 25, 33,
20, 24, 23, 32, 44, 46,
22, 31, 53, 52, 51, 7,
6,  19, 18, 29, 37, 30,
36, 35, 43, 42, 16, 41, 
50, 49, 48, 47, 8,  5
};
#endif

static Shortword sync_bit = 0; /* sync bit */

void melp_chn_write(struct melp_param *par)

{
    Shortword i, bit_cntr;
    UShortword *bit_ptr; 
    
    /* FEC: code additional information in redundant indeces */
    fec_code(par);
    
    /*	Fill bit buffer	*/
    bit_ptr = bit_buffer;
    bit_cntr = 0;

    pack_code(par->gain_index[1],&bit_ptr,&bit_cntr,5,1);
    
    /* Toggle and write sync bit */
    if (sync_bit)
	sync_bit = 0;
    else
	sync_bit = 1;
    pack_code(sync_bit,&bit_ptr,&bit_cntr,1,1);
    pack_code(par->gain_index[0],&bit_ptr,&bit_cntr,3,1);
    pack_code(par->pitch_index,&bit_ptr,&bit_cntr,PIT_BITS,1);
    pack_code(par->jit_index,&bit_ptr,&bit_cntr,1,1);
    pack_code(par->bpvc_index,&bit_ptr,&bit_cntr,NUM_BANDS-1,1);
    
    for (i = 0; i < par->msvq_stages; i++) 
      pack_code(par->msvq_index[i],&bit_ptr,&bit_cntr,par->msvq_bits[i],1);
    
    pack_code(par->fsvq_index[0],&bit_ptr,&bit_cntr,
	      FS_BITS,1);
    
    /*	Write channel output buffer	*/
    for (i = 0; i < NUM_CH_BITS; i++) {
	pack_code(bit_buffer[bit_order[i]],&par->chptr,&par->chbit,
		  1,CHWORDSIZE);
	if (i == 0)
	  *(par->chptr) |= (UShortword)0x8000; /* set beginning of frame bit */
    }

}


Shortword melp_chn_read(struct melp_param *par, struct melp_param *prev_par)
{
    Shortword erase = 0;
    Shortword i, bit_cntr;
    UShortword *bit_ptr; 

    /*	Read channel output buffer into bit buffer */
    bit_ptr = bit_buffer;
    for (i = 0; i < NUM_CH_BITS; i++) {
	erase |= unpack_code(&par->chptr,&par->chbit,
			     (Shortword *)&bit_buffer[bit_order[i]],
			     1,CHWORDSIZE,ERASE_MASK);
	bit_ptr++;
    }

    /*	Read information from  bit buffer	*/
    bit_ptr = bit_buffer;
    bit_cntr = 0;

    unpack_code(&bit_ptr,&bit_cntr,&par->gain_index[1],5,1,0);
    
    /* Read sync bit */
    unpack_code(&bit_ptr,&bit_cntr,&i,1,1,0);
    unpack_code(&bit_ptr,&bit_cntr,&par->gain_index[0],3,1,0);
    unpack_code(&bit_ptr,&bit_cntr,&par->pitch_index,PIT_BITS,1,0);
    
    unpack_code(&bit_ptr,&bit_cntr,&par->jit_index,1,1,0);
    unpack_code(&bit_ptr,&bit_cntr,&par->bpvc_index,
			 NUM_BANDS-1,1,0);
    
    for (i = 0; i < par->msvq_stages; i++) 
      unpack_code(&bit_ptr,&bit_cntr,&par->msvq_index[i],
			   par->msvq_bits[i],1,0);

    unpack_code(&bit_ptr,&bit_cntr,&par->fsvq_index[0],
			 FS_BITS,1,0);
    
    /* Clear unvoiced flag */
    par->uv_flag = 0;
    
    erase = fec_decode(par,erase);
    
    /* Decode new frame if no erasures occurred */
    if (erase) {
	
	/* Erasure: frame repeat */
		
	/* Save correct values of pointers */
	prev_par->chptr = par->chptr;
	prev_par->chbit = par->chbit;
	*par = *prev_par; 
		
	/* Force all subframes to equal last one */
	for (i = 0; i < NUM_GAINFR-1; i++) {
	    par->gain[i] = par->gain[NUM_GAINFR-1];
	}
    }
    else {
	
	/* Decode line spectrum frequencies	*/
	vq_msd2(msvq_cb,&par->lsf[1],msvq_cb_mean,(Shortword*)NULL,
		par->msvq_index,par->msvq_levels,par->msvq_stages,LPC_ORD,0,2);
	i = FS_LEVELS;
	if (par->uv_flag)
	  fill(par->fs_mag,(Shortword)ONE_Q13,(Shortword)NUM_HARM);
	else
	  {	
	      /* Decode Fourier magnitudes */
	      vq_msd2(fsvq_cb,par->fs_mag,(Shortword*)NULL,(Shortword*)NULL,
		      par->fsvq_index,&i,1,(Shortword)NUM_HARM,0,0);
	  }

	/* Decode gain terms with uniform log quantizer	*/
	q_gain_dec(par->gain,par->gain_index,(Shortword)GN_QLO_Q8,
		   (Shortword)GN_QUP_Q8,GN_QLEV_M1_Q10,5);

	/* Fractional pitch: */
	/* Decode logarithmic pitch period */
	if (par->uv_flag)
	  par->pitch = (Shortword)UV_PITCH_Q7;
	else 
	  {
	      quant_u_dec(par->pitch_index,&par->pitch,
			  (Shortword)PIT_QLO_Q12,(Shortword)PIT_QUP_Q12,
			  PIT_QLEV_M1_Q8,7);
	      par->pitch = pow10_fxp(par->pitch,7);
	  }

	/* Decode jitter */
	/* quant_u_dec(par->jit_index,&par->jitter,0.0,MAX_JITTER,2); */
	if (par->jit_index == 0)
	  par->jitter = 0;
	else
	  par->jitter = (Shortword)MAX_JITTER_Q15;

	/* Decode bandpass voicing */
	q_bpvc_dec(&par->bpvc[0],&par->bpvc_index,par->uv_flag,
		   NUM_BANDS);
    }

    /* Return erase flag */
    return(erase);
}