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DSPFUNC.C
资源名称：G711-729.rar [点击查看]
上传用户：meifeng08
上传日期：2013-06-18
资源大小：5304k
文件大小：8k
源码类别：
语音压缩
开发平台：
C/C++
- /* Version 3.3 Last modified: December 26, 1995 */
- #include "typedef.h"
- #include "basic_op.h"
- #include "ld8k.h"
- #include "tab_ld8k.h"
- /*___________________________________________________________________________
- | |
- | Function Name : Pow2() |
- | |
- | L_x = pow(2.0, exponent.fraction) |
- |---------------------------------------------------------------------------|
- | Algorithm: |
- | |
- | The function Pow2(L_x) is approximated by a table and linear |
- | interpolation. |
- | |
- | 1- i = bit10-b15 of fraction, 0 <= i <= 31 |
- | 2- a = bit0-b9 of fraction |
- | 3- L_x = tabpow[i]<<16 - (tabpow[i] - tabpow[i+1]) * a * 2 |
- | 4- L_x = L_x >> (30-exponent) (with rounding) |
- |___________________________________________________________________________|
- */
- Word32 Pow2( /* (o) Q0 : result (range: 0<=val<=0x7fffffff) */
- Word16 exponent, /* (i) Q0 : Integer part. (range: 0<=val<=30) */
- Word16 fraction /* (i) Q15 : Fractional part. (range: 0.0<=val<1.0) */
- )
- {
- Word16 exp, i, a, tmp;
- Word32 L_x;
- L_x = L_mult(fraction, 32); /* L_x = fraction<<6 */
- i = extract_h(L_x); /* Extract b10-b15 of fraction */
- L_x = L_shr(L_x, 1);
- a = extract_l(L_x); /* Extract b0-b9 of fraction */
- a = a & (Word16)0x7fff;
- L_x = L_deposit_h(tabpow[i]); /* tabpow[i] << 16 */
- tmp = sub(tabpow[i], tabpow[i+1]); /* tabpow[i] - tabpow[i+1] */
- L_x = L_msu(L_x, tmp, a); /* L_x -= tmp*a*2 */
- exp = sub(30, exponent);
- L_x = L_shr_r(L_x, exp);
- return(L_x);
- }
- /*___________________________________________________________________________
- | |
- | Function Name : Log2() |
- | |
- | Compute log2(L_x). |
- | L_x is positive. |
- | |
- | if L_x is negative or zero, result is 0. |
- |---------------------------------------------------------------------------|
- | Algorithm: |
- | |
- | The function Log2(L_x) is approximated by a table and linear |
- | interpolation. |
- | |
- | 1- Normalization of L_x. |
- | 2- exponent = 30-exponent |
- | 3- i = bit25-b31 of L_x, 32 <= i <= 63 ->because of normalization. |
- | 4- a = bit10-b24 |
- | 5- i -=32 |
- | 6- fraction = tablog[i]<<16 - (tablog[i] - tablog[i+1]) * a * 2 |
- |___________________________________________________________________________|
- */
- void Log2(
- Word32 L_x, /* (i) Q0 : input value */
- Word16 *exponent, /* (o) Q0 : Integer part of Log2. (range: 0<=val<=30) */
- Word16 *fraction /* (o) Q15: Fractional part of Log2. (range: 0<=val<1) */
- )
- {
- Word16 exp, i, a, tmp;
- Word32 L_y;
- if( L_x <= (Word32)0 )
- {
- *exponent = 0;
- *fraction = 0;
- return;
- }
- exp = norm_l(L_x);
- L_x = L_shl(L_x, exp ); /* L_x is normalized */
- *exponent = sub(30, exp);
- L_x = L_shr(L_x, 9);
- i = extract_h(L_x); /* Extract b25-b31 */
- L_x = L_shr(L_x, 1);
- a = extract_l(L_x); /* Extract b10-b24 of fraction */
- a = a & (Word16)0x7fff;
- i = sub(i, 32);
- L_y = L_deposit_h(tablog[i]); /* tablog[i] << 16 */
- tmp = sub(tablog[i], tablog[i+1]); /* tablog[i] - tablog[i+1] */
- L_y = L_msu(L_y, tmp, a); /* L_y -= tmp*a*2 */
- *fraction = extract_h( L_y);
- return;
- }
- /*___________________________________________________________________________
- | |
- | Function Name : Inv_sqrt |
- | |
- | Compute 1/sqrt(L_x). |
- | L_x is positive. |
- | |
- | if L_x is negative or zero, result is 1 (3fff ffff). |
- |---------------------------------------------------------------------------|
- | Algorithm: |
- | |
- | The function 1/sqrt(L_x) is approximated by a table and linear |
- | interpolation. |
- | |
- | 1- Normalization of L_x. |
- | 2- If (30-exponent) is even then shift right once. |
- | 3- exponent = (30-exponent)/2 +1 |
- | 4- i = bit25-b31 of L_x, 16 <= i <= 63 ->because of normalization. |
- | 5- a = bit10-b24 |
- | 6- i -=16 |
- | 7- L_y = tabsqr[i]<<16 - (tabsqr[i] - tabsqr[i+1]) * a * 2 |
- | 8- L_y >>= exponent |
- |___________________________________________________________________________|
- */
- Word32 Inv_sqrt( /* (o) Q30 : output value (range: 0<=val<1) */
- Word32 L_x /* (i) Q0 : input value (range: 0<=val<=7fffffff) */
- )
- {
- Word16 exp, i, a, tmp;
- Word32 L_y;
- if( L_x <= (Word32)0) return ( (Word32)0x3fffffffL);
- exp = norm_l(L_x);
- L_x = L_shl(L_x, exp ); /* L_x is normalize */
- exp = sub(30, exp);
- if( (exp & 1) == 0 ) /* If exponent even -> shift right */
- L_x = L_shr(L_x, 1);
- exp = shr(exp, 1);
- exp = add(exp, 1);
- L_x = L_shr(L_x, 9);
- i = extract_h(L_x); /* Extract b25-b31 */
- L_x = L_shr(L_x, 1);
- a = extract_l(L_x); /* Extract b10-b24 */
- a = a & (Word16)0x7fff;
- i = sub(i, 16);
- L_y = L_deposit_h(tabsqr[i]); /* tabsqr[i] << 16 */
- tmp = sub(tabsqr[i], tabsqr[i+1]); /* tabsqr[i] - tabsqr[i+1]) */
- L_y = L_msu(L_y, tmp, a); /* L_y -= tmp*a*2 */
- L_y = L_shr(L_y, exp); /* denormalization */
- return(L_y);
- }
