1 /* ------------------------------------------------------------------
2 * Copyright (C) 1998-2009 PacketVideo
4 * Licensed under the Apache License, Version 2.0 (the "License");
5 * you may not use this file except in compliance with the License.
6 * You may obtain a copy of the License at
8 * http://www.apache.org/licenses/LICENSE-2.0
10 * Unless required by applicable law or agreed to in writing, software
11 * distributed under the License is distributed on an "AS IS" BASIS,
12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either
14 * See the License for the specific language governing permissions
15 * and limitations under the License.
16 * -------------------------------------------------------------------
18 /****************************************************************************************
19 Portions of this file are derived from the following 3GPP standard:
22 ANSI-C code for the Adaptive Multi-Rate (AMR) speech codec
23 Available from http://www.3gpp.org
25 (C) 2004, 3GPP Organizational Partners (ARIB, ATIS, CCSA, ETSI, TTA, TTC)
26 Permission to distribute, modify and use this file under the standard license
27 terms listed above has been obtained from the copyright holder.
28 ****************************************************************************************/
33 ------------------------------------------------------------------------------
36 /*----------------------------------------------------------------------------
38 ----------------------------------------------------------------------------*/
42 /*----------------------------------------------------------------------------
44 ; Define module specific macros here
45 ----------------------------------------------------------------------------*/
48 /*----------------------------------------------------------------------------
50 ; Include all pre-processor statements here. Include conditional
51 ; compile variables also.
52 ----------------------------------------------------------------------------*/
54 /*----------------------------------------------------------------------------
55 ; LOCAL FUNCTION DEFINITIONS
56 ; Function Prototype declaration
57 ----------------------------------------------------------------------------*/
59 /*----------------------------------------------------------------------------
60 ; LOCAL STORE/BUFFER/POINTER DEFINITIONS
61 ; Variable declaration - defined here and used outside this module
62 ----------------------------------------------------------------------------*/
66 ------------------------------------------------------------------------------
68 ------------------------------------------------------------------------------
69 INPUT AND OUTPUT DEFINITIONS
72 exponent = Integer part whose valid range is: 0 <= value <= 30 (Word16)
73 fraction = Fractional part whose valid range is 0 <= value < 1
75 pOverflow = pointer to overflow flag
78 L_x = Result of the Pow2() computation (Word32)
79 pOverflow -> 1 if the Pow2() function results in saturation
84 Global Variables Used:
87 Local Variables Needed:
90 ------------------------------------------------------------------------------
93 This function computes L_x = pow(2.0, exponent.fraction)
95 The function Pow2(L_x) is approximated by a table and linear interpolation.
97 1- i = bit10-b15 of fraction, 0 <= i <= 31
98 2- a = bit0-b9 of fraction
99 3- L_x = table[i]<<16 - (table[i] - table[i+1]) * a * 2
100 4- L_x = L_x >> (30-exponent) (with rounding)
102 ------------------------------------------------------------------------------
107 ------------------------------------------------------------------------------
110 pow2.c, UMTS GSM AMR speech codec, R99 - Version 3.2.0, March 2, 2001
112 ------------------------------------------------------------------------------
115 Word32 Pow2 ( // (o) : result (range: 0<=val<=0x7fffffff)
116 Word16 exponent, // (i) : Integer part. (range: 0<=val<=30)
117 Word16 fraction // (i) : Fractional part. (range: 0.0<=val<1.0)
120 Word16 exp, i, a, tmp;
123 L_x = L_mult (fraction, 32); // L_x = fraction<<6
124 i = extract_h (L_x); // Extract b10-b16 of fraction
125 L_x = L_shr (L_x, 1);
126 a = extract_l (L_x); // Extract b0-b9 of fraction
127 a = a & (Word16) 0x7fff;
129 L_x = L_deposit_h (table[i]); // table[i] << 16
130 tmp = sub (table[i], table[i + 1]); // table[i] - table[i+1]
131 L_x = L_msu (L_x, tmp, a); // L_x -= tmp*a*2
133 exp = sub (30, exponent);
134 L_x = L_shr_r (L_x, exp);
139 ------------------------------------------------------------------------------
141 [State any special notes, constraints or cautions for users of this function]
143 ------------------------------------------------------------------------------
146 /*----------------------------------------------------------------------------
148 ----------------------------------------------------------------------------*/
150 OSCL_EXPORT_REF Word32 Pow2( /* (o) : result (range: 0<=val<=0x7fffffff) */
151 Word16 exponent, /* (i) : Integer part. (range: 0<=val<=30) */
152 Word16 fraction, /* (i) : Fractional part. (range: 0.0<=val<1.0) */
156 Word16 exp, i, a, tmp;
159 L_x = L_mult(fraction, 32, pOverflow); /* L_x = fraction<<6 */
161 /* Extract b0-b16 of fraction */
163 i = ((Word16)(L_x >> 16)) & 31; /* ensure index i is bounded */
164 a = (Word16)((L_x >> 1) & 0x7fff);
166 L_x = ((Word32) pow2_tbl[i] << 16); /* pow2_tbl[i] << 16 */
168 /* pow2_tbl[i] - pow2_tbl[i+1] */
169 tmp = pow2_tbl[i] - pow2_tbl[i + 1];
170 L_x = L_msu(L_x, tmp, a, pOverflow); /* L_x -= tmp*a*2 */
173 L_x = L_shr_r(L_x, exp, pOverflow);