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Diffstat (limited to 'media/libstagefright/codecs/amrnb/common/src/log2_norm.cpp')
| -rw-r--r-- | media/libstagefright/codecs/amrnb/common/src/log2_norm.cpp | 238 |
1 files changed, 238 insertions, 0 deletions
diff --git a/media/libstagefright/codecs/amrnb/common/src/log2_norm.cpp b/media/libstagefright/codecs/amrnb/common/src/log2_norm.cpp new file mode 100644 index 0000000..feda874 --- /dev/null +++ b/media/libstagefright/codecs/amrnb/common/src/log2_norm.cpp @@ -0,0 +1,238 @@ +/* ------------------------------------------------------------------ + * 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. +****************************************************************************************/ +/* + + Pathname: ./audio/gsm-amr/c/src/log2_norm.c + +------------------------------------------------------------------------------ + REVISION HISTORY + + Description: Created separate file for Log2_norm function. + + Description: Synchronized file with UMTS version 3.2.0. Updated coding + template. Removed unnecessary include file. + + Description: Made the following changes per comments from Phase 2/3 review: + 1. Modified code to improve performance. + 2. Fixed typecasting issue with TI C compiler. + 3. Added more comments to the code. + + Description: Removed unnecessary line of code (line 208). + + Description: Removed inclusion of "log2.tab" + + Who: Date: + Description: + +------------------------------------------------------------------------------ +*/ + +/*---------------------------------------------------------------------------- +; INCLUDES +----------------------------------------------------------------------------*/ +#include "log2_norm.h" + +/*---------------------------------------------------------------------------- +; MACROS +; Define module specific macros here +----------------------------------------------------------------------------*/ + + +/*---------------------------------------------------------------------------- +; DEFINES +; Include all pre-processor statements here. Include conditional +; compile variables also. +----------------------------------------------------------------------------*/ + +/*---------------------------------------------------------------------------- +; LOCAL FUNCTION DEFINITIONS +; Function Prototype declaration +----------------------------------------------------------------------------*/ + +/*---------------------------------------------------------------------------- +; LOCAL STORE/BUFFER/POINTER DEFINITIONS +; Variable declaration - defined here and used outside this module +----------------------------------------------------------------------------*/ + + +/* +------------------------------------------------------------------------------ + FUNCTION NAME: Log2_norm +------------------------------------------------------------------------------ + INPUT AND OUTPUT DEFINITIONS + + Inputs: + L_x = normalized input value of type Word32 + exp = number of shifts required to normalize L_x; it is of type Word16 + exponent = pointer to the integer part of Log2 (of type Word16) + whose valid range is: 0 <= value <= 30 + fraction = pointer to the fractional part of Log2 (of type Word16) + whose valid range is: 0 <= value < 1 + + Outputs: + exponent points to the newly calculated integer part of Log2 + fraction points to the newly calculated fractional part of Log2 + + Returns: + None + + Global Variables Used: + None + + Local Variables Needed: + table = Log2 table of constants of type Word16 + +------------------------------------------------------------------------------ + FUNCTION DESCRIPTION + + The function Log2(L_x) calculates the logarithm of the normalized input + buffer L_x. The logarithm is approximated by a table and linear + interpolation. The following steps are used to compute Log2(L_x): + + 1. exponent = 30 - norm_exponent + 2. i = bit25-b31 of L_x; 32<=i<=63 (because of normalization). + 3. a = bit10-b24 + 4. i = i - 32 + 5. fraction = table[i]<<16 - (table[i] - table[i+1]) * a * 2 + +------------------------------------------------------------------------------ + REQUIREMENTS + + None + +------------------------------------------------------------------------------ + REFERENCES + + log2.c, UMTS GSM AMR speech codec, R99 - Version 3.2.0, March 2, 2001 + +------------------------------------------------------------------------------ + PSEUDO-CODE + +void Log2_norm ( + Word32 L_x, // (i) : input value (normalized) + Word16 exp, // (i) : norm_l (L_x) + Word16 *exponent, // (o) : Integer part of Log2. (range: 0<=val<=30) + Word16 *fraction // (o) : Fractional part of Log2. (range: 0<=val<1) +) +{ + Word16 i, a, tmp; + Word32 L_y; + + if (L_x <= (Word32) 0) + { + *exponent = 0; + *fraction = 0; + return; + } + + *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 (table[i]); // table[i] << 16 + tmp = sub (table[i], table[i + 1]); // table[i] - table[i+1] + L_y = L_msu (L_y, tmp, a); // L_y -= tmp*a*2 + + *fraction = extract_h (L_y); + + return; +} + +------------------------------------------------------------------------------ + 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] + +------------------------------------------------------------------------------ +*/ + +void Log2_norm( + Word32 L_x, /* (i) : input value (normalized) */ + Word16 exp, /* (i) : norm_l (L_x) */ + Word16 *exponent, /* (o) : Integer part of Log2. (range: 0<=val<=30)*/ + Word16 *fraction /* (o) : Fractional part of Log2. (range: 0<=val<1) */ +) +{ + Word16 i, a, tmp; + Word32 L_y; + + if (L_x <= (Word32) 0) + { + *exponent = 0; + *fraction = 0; + } + else + { + /* Calculate exponent portion of Log2 */ + *exponent = 30 - exp; + + /* At this point, L_x > 0 */ + /* Shift L_x to the right by 10 to extract bits 10-31, */ + /* which is needed to calculate fractional part of Log2 */ + L_x >>= 10; + i = (Word16)(L_x >> 15); /* Extract b25-b31 */ + a = L_x & 0x7fff; /* Extract b10-b24 of fraction */ + + /* Calculate table index -> subtract by 32 is done for */ + /* proper table indexing, since 32<=i<=63 (due to normalization) */ + i -= 32; + + /* Fraction part of Log2 is approximated by using table[] */ + /* and linear interpolation, i.e., */ + /* fraction = table[i]<<16 - (table[i] - table[i+1]) * a * 2 */ + L_y = (Word32) log2_tbl[i] << 16; /* table[i] << 16 */ + tmp = log2_tbl[i] - log2_tbl[i + 1]; /* table[i] - table[i+1] */ + L_y -= (((Word32) tmp) * a) << 1; /* L_y -= tmp*a*2 */ + + *fraction = (Word16)(L_y >> 16); + } + + return; +} |