| /* |
| * 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. |
| */ |
| |
| /****************************************************************************************/ |
| /* */ |
| /* Includes */ |
| /* */ |
| /****************************************************************************************/ |
| |
| #include "LVEQNB_Private.h" |
| #include <math.h> |
| |
| /****************************************************************************************/ |
| /* */ |
| /* Defines */ |
| /* */ |
| /****************************************************************************************/ |
| |
| #define PI 3.14159265358979 |
| |
| /****************************************************************************************/ |
| /* */ |
| /* FUNCTION: LVEQNB_DoublePrecCoefs */ |
| /* */ |
| /* DESCRIPTION: */ |
| /* Calculate double precision coefficients for a peaking filter */ |
| /* */ |
| /* PARAMETERS: */ |
| /* Fs Sampling frequency index */ |
| /* pFilterDefinition Pointer to the filter definition */ |
| /* pCoefficients Pointer to the coefficients */ |
| /* */ |
| /* RETURNS: */ |
| /* LVEQNB_SUCCESS Always succeeds */ |
| /* */ |
| /* NOTES: */ |
| /* 1. The equations used are as follows: */ |
| /* */ |
| /* G = 10^(GaindB/20) - 1 */ |
| /* t0 = 2 * Pi * Fc / Fs */ |
| /* D = 1 if GaindB >= 0 */ |
| /* D = 1 / (1 + G) if GaindB < 0 */ |
| /* */ |
| /* b2 = -0.5 * (2Q - D * t0) / (2Q + D * t0) */ |
| /* b1 = (0.5 - b2) * (1 - coserr(t0)) */ |
| /* a0 = (0.5 + b2) / 2 */ |
| /* */ |
| /* Where: */ |
| /* GaindB is the gain in dBs, range -15dB to +15dB */ |
| /* Fc is the centre frequency, DC to Fs/50 */ |
| /* Fs is the sample frequency, 8000 to 48000 in descrete steps */ |
| /* Q is the Q factor, 0.25 to 12 (represented by 25 to 1200) */ |
| /* */ |
| /* 2. The double precision coefficients are only used when fc is less than fs/85, so */ |
| /* the cosine of t0 is always close to 1.0. Instead of calculating the cosine */ |
| /* itself the difference from the value 1.0 is calculated, this can be done with */ |
| /* lower precision maths. */ |
| /* */ |
| /* 3. The value of the B2 coefficient is only calculated as a single precision value, */ |
| /* small errors in this value have a combined effect on the Q and Gain but not the */ |
| /* the frequency of the filter. */ |
| /* */ |
| /****************************************************************************************/ |
| |
| /****************************************************************************************/ |
| /* */ |
| /* FUNCTION: LVEQNB_SinglePrecCoefs */ |
| /* */ |
| /* DESCRIPTION: */ |
| /* Calculate single precision coefficients for a peaking filter */ |
| /* */ |
| /* PARAMETERS: */ |
| /* Fs Sampling frequency index */ |
| /* pFilterDefinition Pointer to the filter definition */ |
| /* pCoefficients Pointer to the coefficients */ |
| /* */ |
| /* RETURNS: */ |
| /* LVEQNB_SUCCESS Always succeeds */ |
| /* */ |
| /* NOTES: */ |
| /* 1. The equations used are as follows: */ |
| /* */ |
| /* G = 10^(GaindB/20) - 1 */ |
| /* t0 = 2 * Pi * Fc / Fs */ |
| /* D = 1 if GaindB >= 0 */ |
| /* D = 1 / (1 + G) if GaindB < 0 */ |
| /* */ |
| /* b2 = -0.5 * (2Q - D * t0) / (2Q + D * t0) */ |
| /* b1 = (0.5 - b2) * cos(t0) */ |
| /* a0 = (0.5 + b2) / 2 */ |
| /* */ |
| /* Where: */ |
| /* GaindB is the gain in dBs, range -15dB to +15dB */ |
| /* Fc is the centre frequency, DC to Nyquist */ |
| /* Fs is the sample frequency, 8000 to 48000 in descrete steps */ |
| /* Q is the Q factor, 0.25 to 12 */ |
| /* */ |
| /****************************************************************************************/ |
| |
| LVEQNB_ReturnStatus_en LVEQNB_SinglePrecCoefs(LVM_UINT16 Fs, |
| LVEQNB_BandDef_t *pFilterDefinition, |
| PK_FLOAT_Coefs_t *pCoefficients) |
| { |
| |
| extern LVM_FLOAT LVEQNB_GainTable[]; |
| extern LVM_FLOAT LVEQNB_TwoPiOnFsTable[]; |
| extern LVM_FLOAT LVEQNB_DTable[]; |
| |
| /* |
| * Get the filter definition |
| */ |
| LVM_INT16 Gain = pFilterDefinition->Gain; |
| LVM_UINT16 Frequency = pFilterDefinition->Frequency; |
| /* As mentioned in effectbundle.h */ |
| LVM_FLOAT QFactor = (LVM_FLOAT)pFilterDefinition->QFactor / 100.0f; |
| |
| /* |
| * Intermediate variables and temporary values |
| */ |
| LVM_FLOAT T0; |
| LVM_FLOAT D; |
| LVM_FLOAT A0; |
| LVM_FLOAT B1; |
| LVM_FLOAT B2; |
| |
| /* |
| * Calculating the intermediate values |
| */ |
| T0 = Frequency * LVEQNB_TwoPiOnFsTable[Fs]; /* T0 = 2 * Pi * Fc / Fs */ |
| if (Gain >= 0) |
| { |
| D = LVEQNB_DTable[15]; /* D = 1 if GaindB >= 0 */ |
| } |
| else |
| { |
| D = LVEQNB_DTable[Gain + 15]; /* D = 1 / (1 + G) if GaindB < 0 */ |
| } |
| |
| /* |
| * Calculate the B2,B1,A0 coefficients |
| */ |
| B2 = -0.5 * (2 * QFactor - D * T0) / (2 * QFactor + D * T0); |
| B1 = (0.5 - B2) * cos(T0); |
| A0 = (0.5 + B2) / 2.0; |
| |
| /* |
| * Write coeff into the data structure |
| */ |
| /* all the coefficients are multiplied with 2 to make them align with fixed point values*/ |
| pCoefficients->A0 = 2 * A0; |
| pCoefficients->B1 = 2 * B1; |
| pCoefficients->B2 = 2 * B2; |
| pCoefficients->G = LVEQNB_GainTable[Gain + 15]; |
| |
| return(LVEQNB_SUCCESS); |
| } |
