xref: /frameworks/av/media/libstagefright/codecs/amrwbenc/src/preemph.c

/*
 ** Copyright 2003-2010, VisualOn, Inc.
 **
 ** 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.
 */

/***********************************************************************
*      File: preemph.c                                                *
*                                                                     *
*      Description: Preemphasis: filtering through 1 - g z^-1         *
*              Preemph2 --> signal is multiplied by 2             *
*                                                                     *
************************************************************************/

#include "typedef.h"
#include "basic_op.h"

void Preemph(
        Word16 x[],                           /* (i/o)   : input signal overwritten by the output */
        Word16 mu,                            /* (i) Q15 : preemphasis coefficient                */
        Word16 lg,                            /* (i)     : lenght of filtering                    */
        Word16 * mem                          /* (i/o)   : memory (x[-1])                         */
        )
{
    Word16 temp;
    Word32 i, L_tmp;

    temp = x[lg - 1];

    for (i = lg - 1; i > 0; i--)
    {
        L_tmp = L_deposit_h(x[i]);
        L_tmp -= (x[i - 1] * mu)<<1;
        x[i] = (L_tmp + 0x8000)>>16;
    }

    L_tmp = L_deposit_h(x[0]);
    L_tmp -= ((*mem) * mu)<<1;
    x[0] = (L_tmp + 0x8000)>>16;

    *mem = temp;

    return;
}


void Preemph2(
        Word16 x[],                           /* (i/o)   : input signal overwritten by the output */
        Word16 mu,                            /* (i) Q15 : preemphasis coefficient                */
        Word16 lg,                            /* (i)     : lenght of filtering                    */
        Word16 * mem                          /* (i/o)   : memory (x[-1])                         */
         )
{
    Word16 temp;
    Word32 i, L_tmp;

    temp = x[lg - 1];

    for (i = (Word16) (lg - 1); i > 0; i--)
    {
        L_tmp = L_deposit_h(x[i]);
        L_tmp -= (x[i - 1] * mu)<<1; // only called with mu == 22282, so this won't overflow
        if (L_tmp > INT32_MAX / 2) {
            L_tmp = INT32_MAX / 2;
        }
        L_tmp = (L_tmp << 1);
        if (L_tmp > INT32_MAX - 0x8000) {
            L_tmp = INT32_MAX - 0x8000;
        }
        x[i] = (L_tmp + 0x8000)>>16;
    }

    L_tmp = L_deposit_h(x[0]);
    L_tmp -= ((*mem) * mu)<<1;
    if (L_tmp > INT32_MAX / 2) {
        L_tmp = INT32_MAX / 2;
    }
    L_tmp = (L_tmp << 1);
    if (L_tmp > INT32_MAX - 0x8000) {
        L_tmp = INT32_MAX - 0x8000;
    }
    x[0] = (L_tmp + 0x8000)>>16;

    *mem = temp;

    return;
}