bt/embdrv/sbc/encoder/srce/sbc_enc_bit_alloc_mono.c

/******************************************************************************
 *
 *  Copyright (C) 1999-2012 Broadcom Corporation
 *
 *  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.
 *
 ******************************************************************************/

/******************************************************************************
 *
 *  This file contains the code for bit allocation algorithm. It calculates
 *  the number of bits required for the encoded stream of data.
 *
 ******************************************************************************/

/*Includes*/
#include "sbc_encoder.h"
#include "sbc_enc_func_declare.h"

/*global arrays*/
const int16_t sbc_enc_as16Offset4[4][4] = {  {-1, 0, 0, 0}, {-2, 0, 0, 1},
                                    {-2, 0, 0, 1}, {-2, 0, 0, 1} };
const int16_t sbc_enc_as16Offset8[4][8] = {  {-2, 0, 0, 0, 0, 0, 0, 1},
                                    {-3, 0, 0, 0, 0, 0, 1, 2},
                                    {-4, 0, 0, 0, 0, 0, 1, 2},
                                    {-4, 0, 0, 0, 0, 0, 1, 2} };

/****************************************************************************
* BitAlloc - Calculates the required number of bits for the given scale factor
* and the number of subbands.
*
* RETURNS : N/A
*/

void sbc_enc_bit_alloc_mono(SBC_ENC_PARAMS *pstrCodecParams)
{
    int32_t s32MaxBitNeed;   /*to store the max bits needed per sb*/
    int32_t s32BitCount;     /*the used number of bits*/
    int32_t s32SliceCount;   /*to store hwo many slices can be put in bitpool*/
    int32_t s32BitSlice;     /*number of bitslices in bitpool*/
    int32_t s32Sb;           /*counter for sub-band*/
    int32_t s32Ch;           /*counter for channel*/
    int16_t *ps16BitNeed;    /*temp memory to store required number of bits*/
    int32_t s32Loudness;     /*used in Loudness calculation*/
    int16_t *ps16GenBufPtr;
    int16_t *ps16GenArrPtr;
    int16_t *ps16GenTabPtr;
    int32_t  s32NumOfSubBands = pstrCodecParams->s16NumOfSubBands;

    ps16BitNeed = pstrCodecParams->s16ScartchMemForBitAlloc;

    for (s32Ch = 0; s32Ch < pstrCodecParams->s16NumOfChannels; s32Ch++)
    {
        ps16GenBufPtr = ps16BitNeed + s32Ch*s32NumOfSubBands;
        ps16GenArrPtr = pstrCodecParams->as16Bits+s32Ch*SBC_MAX_NUM_OF_SUBBANDS;

        /* bitneed values are derived from scale factor */
        if (pstrCodecParams->s16AllocationMethod == SBC_SNR)
        {
            ps16BitNeed = pstrCodecParams->as16ScaleFactor;
            ps16GenBufPtr = ps16BitNeed + s32Ch * s32NumOfSubBands;
        }
        else
        {
            ps16GenBufPtr = ps16BitNeed + s32Ch*s32NumOfSubBands;
            if(s32NumOfSubBands == 4)
            {
                ps16GenTabPtr = (int16_t *)
                    sbc_enc_as16Offset4[pstrCodecParams->s16SamplingFreq];
            }
            else
            {
                ps16GenTabPtr = (int16_t *)
                    sbc_enc_as16Offset8[pstrCodecParams->s16SamplingFreq];
            }
            for(s32Sb=0; s32Sb<s32NumOfSubBands; s32Sb++)
            {
                if(pstrCodecParams->as16ScaleFactor[s32Ch*s32NumOfSubBands+s32Sb] == 0)
                    *(ps16GenBufPtr) = -5;
                else
                {
                    s32Loudness =
                        (int32_t)(pstrCodecParams->as16ScaleFactor[s32Ch*s32NumOfSubBands+s32Sb]
                                                            - *ps16GenTabPtr);
                    if(s32Loudness > 0)
                        *(ps16GenBufPtr) = (int16_t)(s32Loudness >>1);
                    else
                        *(ps16GenBufPtr) = (int16_t)s32Loudness;
                }
                ps16GenBufPtr++;
                ps16GenTabPtr++;
            }

        }

        /* max bitneed index is searched*/
        s32MaxBitNeed = 0;
        ps16GenBufPtr = ps16BitNeed + s32Ch*s32NumOfSubBands;
        for(s32Sb=0; s32Sb<s32NumOfSubBands; s32Sb++)
        {
            if( *(ps16GenBufPtr) > s32MaxBitNeed)
                s32MaxBitNeed = *(ps16GenBufPtr);

            ps16GenBufPtr++;
        }
        ps16GenBufPtr = ps16BitNeed + s32Ch*s32NumOfSubBands;
        /*iterative process to find hwo many bitslices fit into the bitpool*/
        s32BitSlice = s32MaxBitNeed + 1;
        s32BitCount = pstrCodecParams->s16BitPool;
        s32SliceCount = 0;
        do
        {
            s32BitSlice --;
            s32BitCount -= s32SliceCount;
            s32SliceCount = 0;

            for(s32Sb=0; s32Sb<s32NumOfSubBands; s32Sb++)
            {
                if( (((*ps16GenBufPtr-s32BitSlice)< 16) && (*ps16GenBufPtr-s32BitSlice) >= 1))
                {
                    if((*ps16GenBufPtr-s32BitSlice) == 1)
                        s32SliceCount+=2;
                    else
                        s32SliceCount++;
                }
                ps16GenBufPtr++;

            }/*end of for*/
            ps16GenBufPtr = ps16BitNeed + s32Ch*s32NumOfSubBands;
        }while(s32BitCount-s32SliceCount>0);

        if(s32BitCount == 0)
        {
            s32BitCount -= s32SliceCount;
            s32BitSlice --;
        }

        /*Bits are distributed until the last bitslice is reached*/
        ps16GenArrPtr = pstrCodecParams->as16Bits+s32Ch*s32NumOfSubBands;
        ps16GenBufPtr = ps16BitNeed + s32Ch*s32NumOfSubBands;
        for(s32Sb=0; s32Sb<s32NumOfSubBands; s32Sb++)
        {
            if(*(ps16GenBufPtr) < s32BitSlice+2)
                *(ps16GenArrPtr) = 0;
            else
                *(ps16GenArrPtr) = ((*(ps16GenBufPtr)-s32BitSlice)<16) ?
                    (int16_t)(*(ps16GenBufPtr)-s32BitSlice) : 16;

            ps16GenBufPtr++;
            ps16GenArrPtr++;
        }
        ps16GenArrPtr = pstrCodecParams->as16Bits+s32Ch*s32NumOfSubBands;
        ps16GenBufPtr = ps16BitNeed + s32Ch*s32NumOfSubBands;
        /*the remaining bits are allocated starting at subband 0*/
        s32Sb=0;
        while( (s32BitCount > 0) && (s32Sb < s32NumOfSubBands) )
        {
            if( (*(ps16GenArrPtr) >= 2) && (*(ps16GenArrPtr) < 16) )
            {
                (*(ps16GenArrPtr))++;
                s32BitCount--;
            }
            else if( (*(ps16GenBufPtr) == s32BitSlice+1) &&
                (s32BitCount > 1) )
            {
                *(ps16GenArrPtr) = 2;
                s32BitCount -= 2;
            }
            s32Sb++;
            ps16GenArrPtr++;
            ps16GenBufPtr++;
        }
        ps16GenArrPtr = pstrCodecParams->as16Bits+s32Ch*s32NumOfSubBands;


        s32Sb=0;
        while( (s32BitCount > 0) && (s32Sb < s32NumOfSubBands) )
        {
            if( *(ps16GenArrPtr) < 16)
            {
                (*(ps16GenArrPtr))++;
                s32BitCount--;
            }
            s32Sb++;
            ps16GenArrPtr++;
        }
    }
}
/*End of BitAlloc() function*/