Qt解码播放ADPCM

    p_audioFormat = new QAudioFormat;

    p_audioFormat->setSampleRate(8000);

    p_audioFormat->setChannelCount(1);

    p_audioFormat->setSampleSize(16);

    p_audioFormat->setCodec("audio/pcm");

    p_audioFormat->setByteOrder(QAudioFormat::LittleEndian);    //大小端；

    p_audioFormat->setSampleType(QAudioFormat::UnSignedInt);    //有无符合；

    p_audioOutput = new QAudioOutput(*p_audioFormat,this);

    device = p_audioOutput->start();                    //QIODevice类

    QTimer *mytimer = new QTimer(this);         //控制播发；因为设备内存有大小，我的是640byte；

    connect(mytimer,SIGNAL(timeout()),this,SLOT(my_timer_out()));

mytimer->start(100);

前四个字节是上一个PCM数据，未压缩的PCM；

index = a[2];

        valpred = *((short*)a);

        int delta; 

        int count=0;

        unsigned int step;

        bool odd = true;

        int sign;

for(int i=4; i<256; ){

            if(odd) {

                delta = a[i]&0x0f;

            }

            else {

                delta = (uchar)a[i]>>4;

            }

            if(index<0) index = 0;

            if(index>88) index = 88;

            sign = delta & 8;

            delta = delta & 7;

            step = stepsizeTable[index];

            vpdiff = step >> 3;

            if( (delta & 4) !=0 ) vpdiff += step;

            if( (delta & 2) !=0 ) vpdiff += step>>1;

            if( (delta & 1) !=0 ) vpdiff += step>>2;

            index += indexTable[delta];

            if( sign != 0 ) {

                valpred -= vpdiff;

                if(valpred < -32768)

                    valpred = -32768;

            }

            else {

                valpred += vpdiff;

                if(valpred > 32767)

                    valpred = 32767;

            }

            music.append((char*)&valpred,2);

            odd = !odd;

            if(odd)i++;

        }

void Widget::my_timer_out() //音质流畅；

{

        while(p_audioOutput->bytesFree()>=p_audioOutput->periodSize()) {

            if(music.size()periodSize())break;

            device->write(music.data(),p_audioOutput->periodSize());

            music=music.mid(p_audioOutput->periodSize());

        }

}