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1  /* ------------------------------------------------------------------
2   * Copyright (C) 1998-2009 PacketVideo
3   *
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
7   *
8   *      http://www.apache.org/licenses/LICENSE-2.0
9   *
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
13   * express or implied.
14   * See the License for the specific language governing permissions
15   * and limitations under the License.
16   * -------------------------------------------------------------------
17   */
18  /****************************************************************************************
19  Portions of this file are derived from the following 3GPP standard:
20  
21      3GPP TS 26.073
22      ANSI-C code for the Adaptive Multi-Rate (AMR) speech codec
23      Available from http://www.3gpp.org
24  
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  ****************************************************************************************/
29  /*
30  
31   Filename: /audio/gsm_amr/c/src/round.c
32  
33  ------------------------------------------------------------------------------
34   REVISION HISTORY
35  
36   Description: Created separate file for the round function. Sync'ed up
37            with the current template and fixed tabs.
38  
39   Description: Made changes based on review meeting:
40                1. Removed long in Inputs Definitions.
41                2. Changed L_var1 to var_out and description in
42                   Output Definitions.
43  
44   Description: Added a parameter to the function interface, pOverflow which is
45                a pointer to the overflow flag. This flag is required by the
46                L_add() function invoked by round().
47                Removed code that updates the MOPS counter.
48                Created a new return variable result.
49  
50   Description: Removed embedded tabs. Included comment in the Pseudo code
51                Section about using pointer to overflow flag in the actual
52                implementation instead of using a global flag.
53  
54   Description: Changed function name to pv_round to avoid conflict with
55                round function in C standard library.
56  
57   Who:                       Date:
58   Description:
59  
60  ------------------------------------------------------------------------------
61   MODULE DESCRIPTION
62  
63   Rounding function with saturation.
64  
65  ------------------------------------------------------------------------------
66  */
67  
68  /*----------------------------------------------------------------------------
69  ; INCLUDES
70  ----------------------------------------------------------------------------*/
71  #include    "basic_op.h"
72  
73  /*----------------------------------------------------------------------------
74  ; MACROS
75  ; [Define module specific macros here]
76  ----------------------------------------------------------------------------*/
77  
78  /*----------------------------------------------------------------------------
79  ; DEFINES
80  ; [Include all pre-processor statements here. Include conditional
81  ; compile variables also.]
82  ----------------------------------------------------------------------------*/
83  
84  /*----------------------------------------------------------------------------
85  ; LOCAL FUNCTION DEFINITIONS
86  ; [List function prototypes here]
87  ----------------------------------------------------------------------------*/
88  
89  /*----------------------------------------------------------------------------
90  ; LOCAL VARIABLE DEFINITIONS
91  ; [Variable declaration - defined here and used outside this module]
92  ----------------------------------------------------------------------------*/
93  
94  /*
95  ------------------------------------------------------------------------------
96   FUNCTION NAME: pv_round
97  ------------------------------------------------------------------------------
98   INPUT AND OUTPUT DEFINITIONS
99  
100   Inputs:
101      L_var1 = 32 bit signed integer (Word32) whose value falls
102               in the range : 0x8000 0000 <= L_var1 <= 0x7fff ffff.
103  
104      pOverflow = pointer to overflow (Flag)
105  
106   Outputs:
107      None
108  
109   Returns:
110          result = MS 16 bits of rounded input L_var1.
111  
112   Global Variables Used:
113      None
114  
115   Local Variables Needed:
116      None
117  
118  ------------------------------------------------------------------------------
119   FUNCTION DESCRIPTION
120  
121   This function rounds the lower 16 bits of the 32 bit input number into the
122   MS 16 bits with saturation. Shift the resulting bits right by 16 and return
123   the 16 bit number:
124      pv_round(L_var1) = extract_h(L_add(L_var1,32768))
125  
126  ------------------------------------------------------------------------------
127   REQUIREMENTS
128  
129   None
130  
131  ------------------------------------------------------------------------------
132   REFERENCES
133  
134   [1] round() function in basic_op2.c,  UMTS GSM AMR speech codec, R99 -
135   Version 3.2.0, March 2, 2001
136  
137  ------------------------------------------------------------------------------
138   PSEUDO-CODE
139  
140  Word16 pv_round (Word32 L_var1)
141  {
142      Word16 var_out;
143      Word32 L_rounded;
144  
145  * The reference ETSI code uses a global flag for Overflow in the L_add() function.
146  * In the actual implementation a pointer to Overflow flag is passed in as a
147  * parameter to the function.
148  
149      L_rounded = L_add (L_var1, (Word32) 0x00008000L);
150  #if (WMOPS)
151      multiCounter[currCounter].L_add--;
152  #endif
153      var_out = extract_h (L_rounded);
154  #if (WMOPS)
155      multiCounter[currCounter].extract_h--;
156      multiCounter[currCounter].round++;
157  #endif
158      return (var_out);
159  }
160  
161  ------------------------------------------------------------------------------
162   RESOURCES USED [optional]
163  
164   When the code is written for a specific target processor the
165   the resources used should be documented below.
166  
167   HEAP MEMORY USED: x bytes
168  
169   STACK MEMORY USED: x bytes
170  
171   CLOCK CYCLES: (cycle count equation for this function) + (variable
172                  used to represent cycle count for each subroutine
173                  called)
174       where: (cycle count variable) = cycle count for [subroutine
175                                       name]
176  
177  ------------------------------------------------------------------------------
178   CAUTION [optional]
179   [State any special notes, constraints or cautions for users of this function]
180  
181  ------------------------------------------------------------------------------
182  */
183  
184  /*----------------------------------------------------------------------------
185  ; FUNCTION CODE
186  ----------------------------------------------------------------------------*/
pv_round(register Word32 L_var1,Flag * pOverflow)187  Word16 pv_round(register Word32 L_var1, Flag *pOverflow)
188  {
189      Word16  result;
190  
191      L_var1 = L_add(L_var1, (Word32) 0x00008000L, pOverflow);
192      result = (Word16)(L_var1 >> 16);
193  
194      return (result);
195  }
196