diff options
Diffstat (limited to 'media/libeffects/lvm/lib/Common/src/dB_to_Lin32.c')
| -rwxr-xr-x | media/libeffects/lvm/lib/Common/src/dB_to_Lin32.c | 109 |
1 files changed, 109 insertions, 0 deletions
diff --git a/media/libeffects/lvm/lib/Common/src/dB_to_Lin32.c b/media/libeffects/lvm/lib/Common/src/dB_to_Lin32.c new file mode 100755 index 0000000..ac0343f --- /dev/null +++ b/media/libeffects/lvm/lib/Common/src/dB_to_Lin32.c @@ -0,0 +1,109 @@ +/* + * Copyright (C) 2004-2010 NXP Software + * Copyright (C) 2010 The Android Open Source Project + * + * 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. + */ + +/************************************************************************/ +/* */ +/* %created_by: sra % (CM/S)*/ +/* %name: dB_to_Lin32.c % (CM/S)*/ +/* %version: 2 % (CM/S)*/ +/* %date_created: Wed Jun 18 11:27:46 2008 % (CM/S)*/ +/* */ +/************************************************************************/ + +/*######################################################################################*/ +/* Include files */ +/*######################################################################################*/ + +#include "ScalarArithmetic.h" + + +/**************************************************************************************** + * Name : dB_to_Lin32() + * Input : Signed 16-bit integer + * MSB (16) = sign bit + * (15->05) = integer part + * (04->01) = decimal part + * Output : Signed 32-bit integer + * MSB (32) = sign bit + * (31->16) = integer part + * (15->01) = decimal part + * Returns : Lin value format 1.16.15 + * Description : + * Remarks : Makes an approximation to the conversion by counting the number + * of 6dB steps for use as shifts and then interpolates with a remainder + * with the equation: + * + * Correction = (Remainder / 1.5029) - (Remainder^2 / 6) + * + * The two coefficients are scaled from 0x40000000 in 96 steps and calculated + * as follows: + * + * FIRST_COEF = 0x80000000 / (96 * 1.5029) + * SECOND_COEF = 0x80000000 / (96^2 * 6) + * + ****************************************************************************************/ + +#define FOUR_OVER_SIX 21846 /* (4 / 6) * 2^15 */ +#define SIX_DB 96 /* 6 * 16 or 6dB in Q11.4 format */ +#define FIRST_COEF_NEG 14884305 +#define FIRST_COEF_POS 7442152 /* FIRST_COEF_NEG / 2 */ +#define SECOND_COEF 38836 +#define MAX_VALUE 1536 /* 96 * 16 */ + +LVM_INT32 dB_to_Lin32(LVM_INT16 db_fix) +{ + LVM_INT32 Lin_val_32; + LVM_INT16 Shift; + LVM_INT32 Remain; + + + /* + * Check sign of the input + */ + if (db_fix<0) + { + if (db_fix > -MAX_VALUE) + { + Shift = (LVM_INT16)((((LVM_UINT32)(-db_fix) >> 4) * FOUR_OVER_SIX) >> 17); /* Number of 6dB steps in Q11.4 format */ + Remain = -db_fix - (Shift * SIX_DB); + Remain = (0x7FFFFFFF - (Remain * FIRST_COEF_NEG)) + (Remain * Remain * SECOND_COEF); + Lin_val_32 = (LVM_INT32)((LVM_UINT32)Remain >> (16 + Shift)); + } + else + { + Lin_val_32 = 0; + } + } + else + { + if (db_fix < MAX_VALUE) + { + Shift = (LVM_INT16)((((LVM_UINT32)db_fix >> 4) * FOUR_OVER_SIX) >> 17); /* Number of 6dB steps in Q11.4 format */ + Remain = db_fix - (Shift * SIX_DB); + Remain = 0x3FFFFFFF + (Remain * FIRST_COEF_POS) + (Remain * Remain * SECOND_COEF); + Lin_val_32 = (LVM_INT32)((LVM_UINT32)Remain >> (15 - Shift)); + } + else + { + Lin_val_32 = 0x7FFFFFFF; + } + } + + + return Lin_val_32; /* format 1.16.15 */ +} + |