pcm音量计算

Posted 2022-12-03 xianjian_x

　　以下程序用在16Khz的单声道或者8Khz的双声道的pcm数据的音量计算.
来源自搜索的各种资料加实际测试.
参考源暂未统计出.

　　注意要求的对数函数是log10,不是log.

int pcm_db_count(const unsigned char* ptr, size_t size)

    int ndb = 0;

    short int value;

    int i;
    long v = 0;
    for(i=0; i<size; i+=2)
       
        memcpy((char*)&value, ptr+i, 1); 
        memcpy((char*)&value+1, ptr+i+1, 1); 
        v += abs(value);
       

    v = v/(size/2);

    if(v != 0) 
        ndb = (int)(20.0*log10((double)v / 65535.0 )); 
       
    else 
        ndb = -96;
       

    return ndb;

实际工程中用的代码：

int CalcLoudNess(char * pData,int length,int soundwidth )

    int ndb = 0,i;
    long v = 0;

    if(soundwidth == 16)
        short int value;
        assert(sizeof(short int) == 2 );
        for(i = 0;i < length;i += 2)
        
            *(char *)&value             = *(pData + i);
            *((char *)&value + 1)       = *(pData + i + 1);
            v                           += abs(value);
        
        v       = v / ( length /2) ;
        if(v != 0)
            ndb = (int)(20.0 * log10((double)v / 65535.0 ) );
        else
            ndb = -96;
        
        return ndb;
    else if(soundwidth == 32) 
        /// TODO  32 位音频数据