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Diffstat (limited to 'media/libeffects/lvm/lib/Common/src/NonLinComp_D16.c')
| -rwxr-xr-x | media/libeffects/lvm/lib/Common/src/NonLinComp_D16.c | 125 |
1 files changed, 125 insertions, 0 deletions
diff --git a/media/libeffects/lvm/lib/Common/src/NonLinComp_D16.c b/media/libeffects/lvm/lib/Common/src/NonLinComp_D16.c new file mode 100755 index 0000000..1428777 --- /dev/null +++ b/media/libeffects/lvm/lib/Common/src/NonLinComp_D16.c @@ -0,0 +1,125 @@ +/* + * 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. + */ + +/********************************************************************************** + + $Author: beq07716 $ + $Revision: 1000 $ + $Date: 2010-06-28 13:08:20 +0200 (Mon, 28 Jun 2010) $ + +***********************************************************************************/ + +/****************************************************************************************/ +/* */ +/* Includes */ +/* */ +/****************************************************************************************/ + +#include "CompLim_private.h" + +/****************************************************************************************/ +/* */ +/* FUNCTION: NonLinComp_D16 */ +/* */ +/* DESCRIPTION: */ +/* Non-linear compression by companding. The function works on a sample by sample */ +/* basis by increasing the level near the zero crossing. This gives a ttrade-off */ +/* between THD and compression. It uses the equation: */ +/* */ +/* Output = Input + K * (Input - Input^2) if Input > 0 */ +/* = Input + K * (Input + Input^2) if Input <= 0 */ +/* */ +/* The value of K controls the amount of compression and as a side effect the amount */ +/* distortion introduced. The amount of compression is signal dependent and the values */ +/* given below are approximate. */ +/* */ +/* Gain (fractional) Gain (integer) Compression Pk-Pk THD */ +/* 1.0 32767 +6dB 16dB */ +/* 0.78 25559 +5dB 19dB */ +/* 0.6 19661 +4dB 21dB */ +/* 0.41 13435 +3dB 24dB */ +/* 0.26 8520 +2dB 28dB */ +/* 0.12 3932 +1dB 34dB */ +/* 0.0 0 +0dB 98dB */ +/* */ +/* PARAMETERS: */ +/* Gain - compression control parameter */ +/* pDataIn - pointer to the input data buffer */ +/* pDataOut - pointer to the output data buffer */ +/* BlockLength - number of samples to process */ +/* */ +/* RETURNS: */ +/* None */ +/* */ +/* NOTES: */ +/* */ +/****************************************************************************************/ + +void NonLinComp_D16(LVM_INT16 Gain, + LVM_INT16 *pDataIn, + LVM_INT16 *pDataOut, + LVM_INT32 BlockLength) +{ + + LVM_INT16 Sample; /* Input samples */ + LVM_INT32 SampleNo; /* Sample index */ + LVM_INT16 Temp; + + + /* + * Process a block of samples + */ + for(SampleNo = 0; SampleNo<BlockLength; SampleNo++) + { + + /* + * Read the input + */ + Sample = *pDataIn; + pDataIn++; + + + /* + * Apply the compander, this compresses the signal at the expense of + * harmonic distortion. The amount of compression is control by the + * gain factor + */ + if ((LVM_INT32)Sample != -32768) + { + Temp = (LVM_INT16)((Sample * Sample) >> 15); + if(Sample >0) + { + Sample = (LVM_INT16)(Sample + ((Gain * (Sample - Temp)) >> 15)); + } + else + { + Sample = (LVM_INT16)(Sample + ((Gain * (Sample + Temp)) >> 15)); + } + } + + + /* + * Save the output + */ + *pDataOut = Sample; + pDataOut++; + + + } + +} + |