tone_gen.c

完整的EVRC压缩解压缩算法源码,通过C-C++编译后可以运行!

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#include <stdio.h>
#include <string.h>
//#include <math.h>
#include "typedef.h"
#include "tty.h"
#include "basic_op.h"

#ifndef PI
#define PI              3.14159265358979323846
#endif

#ifndef MIN
#define MIN(x,y)        (((x)<(y)) ? (x) : (y))
#endif

Word16 prev_freq = MARK_FREQ;

/*------------------------------------------------------------------
*       cos(wk) = 2*cos(w)*cos(w(k-1)) - cos(w(k-2))
*
*  Which is of the form:
*
*       y[k] = x*y[k-1] - y[k-2]
*
* Initial conditions:
*       param[0] = 32767*cos(2*PI*freq/8000)            (2*cos(w) in Q14)
*       param[1] = y[-2] = 16384;                       (cos(0)   in Q14)
*       param[2] = y[-1] = 16384*cos(2*PI*freq/8000)    (cos(w)   in Q14)
*------------------------------------------------------------------*/

void tone_gen(
    Word16      outbuf[],       /* (o) output in Q14                    */
    Word16      freq,           /* (i) desired freq in Hz               */
    Word16      volume,         /* (i) gain in Q14                      */
    Word16      len,            /* (i) # of samples to generate         */
    Word16      param[])        /* (i) param[0] = 2*cos(2*PI*freq/8000) */
                                /* (i) param[1] = y[k-2]                */
                                /* (i) param[2] = y[k-1]                */
{

    Word16  i;
    Word32  accA;


    /*** Generate first 2 samples using previous history ***/

    for( i=0 ; i < MIN(len,2) ; i++ )
    {                                                       
        /* outbuf[i] = (((param[0]*param[2])>>14) - param[1]);*/
        accA = L_mult(param[0],param[2]);
        accA = L_shr(accA,15);          /* shr 15 because L_mult adds shl */
        outbuf[i] = extract_l(accA);
        outbuf[i] = sub(outbuf[i],param[1]);

        param[1] = param[2];                               
        param[2] = outbuf[i];                              
    }


    /*** Generate the rest of the samples ***/

    for( i=2 ; i < len ; i++ )
    {
        /* outbuf[i] = (((param[0]*outbuf[i-1])>>14) - outbuf[i-2]);*/
        accA = L_mult(param[0],outbuf[i-1]);
        accA = L_shr(accA,15);          /* shr 15 because L_mult adds shl */
        outbuf[i] = extract_l(accA);
        outbuf[i] = sub(outbuf[i],outbuf[i-2]);
    }

    /*** Update parameters ***/
                                                           
    if( sub(len,2) >= 0 )
    {
        param[1] = outbuf[len-2];                          
        param[2] = outbuf[len-1];                           
    }

    /*** Volume Control ***/

    for( i=0 ; i < len ; i++ )
    {
        accA = L_mult(outbuf[i],volume);    /* Q14*Q14 */
        accA = L_shl(accA,1);
        outbuf[i] = extract_h(accA);
    }

}

/*-------------------------------------------------------------------
*       init_tone_gen()
*--------------------------------------------------------------------*/

void init_tone_gen(
    Word16      param[],        /* (o) tone generation parameters       */
    Word16      freq )          /* (i) Desired freq as 2*cos(w)         */
{

    param[0] = freq;    
    param[1] = 16384;                                           
    param[2] = shr(param[0],1);

} /* end init_tone_gen() */