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Diffstat (limited to 'media/libstagefright/codecs/amrnb/common/src/shr.cpp')
-rw-r--r-- | media/libstagefright/codecs/amrnb/common/src/shr.cpp | 258 |
1 files changed, 258 insertions, 0 deletions
diff --git a/media/libstagefright/codecs/amrnb/common/src/shr.cpp b/media/libstagefright/codecs/amrnb/common/src/shr.cpp new file mode 100644 index 0000000..775dc69 --- /dev/null +++ b/media/libstagefright/codecs/amrnb/common/src/shr.cpp @@ -0,0 +1,258 @@ +/* ------------------------------------------------------------------ + * Copyright (C) 1998-2009 PacketVideo + * + * Licensed under the Apache License, Version 2.0 (the "License"); + * you may not use this file except in compliance with the License. + * You may obtain a copy of the License at + * + * http://www.apache.org/licenses/LICENSE-2.0 + * + * Unless required by applicable law or agreed to in writing, software + * distributed under the License is distributed on an "AS IS" BASIS, + * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either + * express or implied. + * See the License for the specific language governing permissions + * and limitations under the License. + * ------------------------------------------------------------------- + */ +/**************************************************************************************** +Portions of this file are derived from the following 3GPP standard: + + 3GPP TS 26.073 + ANSI-C code for the Adaptive Multi-Rate (AMR) speech codec + Available from http://www.3gpp.org + +(C) 2004, 3GPP Organizational Partners (ARIB, ATIS, CCSA, ETSI, TTA, TTC) +Permission to distribute, modify and use this file under the standard license +terms listed above has been obtained from the copyright holder. +****************************************************************************************/ +/* + + Filename: /audio/gsm_amr/c/src/shr.c + +------------------------------------------------------------------------------ + REVISION HISTORY + + Description: Created separate file for the shr function. Sync'ed up with + the current template and fixed tabs. + + Description: 1. Modified code by seperating var2=0 condition. + 2. Changed Input range definitions. + + Description: Made changes based on review meeting. + 1. Changed Overflow definition. + 2. Removed pseudo-code. + 3. Deleted (var2>15&&var1!=0) condition. + 4. Moved var2>0 condition in front of var2<0 condition. + + Description: Changed the function prototype to pass in a pointer to the + overflow flag instead of using global data. + + Description: Made changes per formal review. Updated template. + Removed code that updates MOPS counter. + Changed parameter name from "overflow" and "pOverflow". + Optimized code by eliminating unnecessary typecasting. + Filled in the PSEUDO CODE section + + Description: Further optimized typecasting for overflow case + + Who: Date: + Description: +------------------------------------------------------------------------------ +------------------------------------------------------------------------------ + MODULE DESCRIPTION + Shift right function with overflow control +------------------------------------------------------------------------------ +*/ + +/*---------------------------------------------------------------------------- +; INCLUDES +----------------------------------------------------------------------------*/ +#include "basic_op.h" + +/*---------------------------------------------------------------------------- +; MACROS +; [Define module specific macros here] +----------------------------------------------------------------------------*/ + +/*---------------------------------------------------------------------------- +; DEFINES +; [Include all pre-processor statements here. Include conditional +; compile variables also.] +----------------------------------------------------------------------------*/ + +/*---------------------------------------------------------------------------- +; LOCAL FUNCTION DEFINITIONS +; [List function prototypes here] +----------------------------------------------------------------------------*/ + +/*---------------------------------------------------------------------------- +; LOCAL VARIABLE DEFINITIONS +; [Variable declaration - defined here and used outside this module] +----------------------------------------------------------------------------*/ + + +/* +------------------------------------------------------------------------------ + FUNCTION NAME: shr +------------------------------------------------------------------------------ + INPUT AND OUTPUT DEFINITIONS + + Inputs: + var1 = 16 bit short signed integer (Word16) whose value falls in + the range : 0xffff 8000 <= var1 <= 0x0000 7fff. + + var2 = 16 bit short signed integer (Word16) whose value falls in + the range : 0xffff 8000 <= var2 <= 0x0000 7fff. + + pOverflow = pointer to overflow (Flag) + + Outputs: + pOverflow -> 1 if the shift operation resulted in overflow + + Returns: + product = Shifted result limited to 16 bits (Word16) + + Global Variables Used: + None + + Local Variables Needed: + None + +------------------------------------------------------------------------------ + FUNCTION DESCRIPTION + + This function arithmetically shifts the 16 bit input var1 right var2 positions + with sign extension. If var2 is negative, arithmetically shift var1 left by + -var2 with sign extension. Saturate the result in case of underflows or + overflows. + +------------------------------------------------------------------------------ + REQUIREMENTS + None +------------------------------------------------------------------------------ + REFERENCES + + [1] shr() function in basic_op2.c, UMTS GSM AMR speech codec, R99 - + Version 3.2.0, March 2, 2001 + +------------------------------------------------------------------------------ + PSEUDO-CODE + +Word16 shr_std (Word16 var1, Word16 var2) +{ + Word16 var_out; + + if (var2 < 0) + { + if (var2 < -16) + var2 = -16; + var_out = shl_std (var1, -var2); +#if (WMOPS) + mult_stdiCounter[currCounter].shl_std--; +#endif + } + else + { + if (var2 >= 15) + { + var_out = (var1 < 0) ? -1 : 0; + } + else + { + if (var1 < 0) + { + var_out = ~((~var1) >> var2); + } + else + { + var_out = var1 >> var2; + } + } + } + +#if (WMOPS) + mult_stdiCounter[currCounter].shr_std++; +#endif + return (var_out); +} +------------------------------------------------------------------------------ + RESOURCES USED [optional] + + When the code is written for a specific target processor the + the resources used should be documented below. + + HEAP MEMORY USED: x bytes + + STACK MEMORY USED: x bytes + + CLOCK CYCLES: (cycle count equation for this function) + (variable + used to represent cycle count for each subroutine + called) + where: (cycle count variable) = cycle count for [subroutine + name] + +------------------------------------------------------------------------------ + CAUTION [optional] + [State any special notes, constraints or cautions for users of this function] + +------------------------------------------------------------------------------ +*/ + +/*---------------------------------------------------------------------------- +; FUNCTION CODE +----------------------------------------------------------------------------*/ +Word16 shr(register Word16 var1, register Word16 var2, Flag *pOverflow) +{ + register Word16 result; + register Word32 temp_res; + + if (var2 != 0) + { + if (var2 > 0) + { + if (var2 >= 15) + { + result = ((var1 < 0) ? -1 : 0); + } + else + { + if (var1 < 0) + { + result = (~((~var1) >> var2)); + } + else + { + result = (var1 >> var2); + } + } + } + else + { + if (var2 < -16) + { + var2 = -16; + } + + var2 = -var2; /* Shift right negative is equivalent */ + /* to shifting left positive. */ + + temp_res = ((Word32) var1) << var2; + result = (Word16)(temp_res); + + if (temp_res != (Word32) result) + { + *pOverflow = 1; + result = ((var1 > 0) ? MAX_16 : MIN_16); + } + } + + } + else + { + result = var1; + } + + return (result); +} + |