如何正确地将十进制MIDI弯音值分成2个分开的7位值？

Question

我正在尝试制作一种自定义midi播放器,为此我使用的数组已经正确记住了midi消息数据,如下所示:

int array[3000][4]={{time,status,data1,data2},{...},...}

当我希望我的程序发送midi消息(以便可以播放)时,我调用此数组并在noteon/off,pitch-bend等之间进行必要的区分.弯音值(范围从0到16383,但通常约为8192,这意味着没有音调移位)全部存储在data1(array [i] [2])中.对于从int转换为两个7位值以传递给midiOutShortMsg(),我使用了一些我在这里找到的代码.这是我实际使用的代码:

union { unsigned long word; unsigned char data[4]; } message;
int main(int argc, char** argv) {
    int midiport; // select which MIDI output port to open
    uint16_t bend;
    int flag,u;    // monitor the status of returning functions
    uint16_t mask = 0x007F;
    HMIDIOUT device;    // MIDI device interface for sending MIDI output
    message.data[0] = 0x90;  
    message.data[1] = 60;    
    message.data[2] = 100;   
    message.data[3] = 0;     // Unused parameter


// Assign the MIDI output port number (from input or default to 0)
if (!midiOutGetNumDevs()){
    printf("non ci sono devices");
}
if (argc < 2) {
    midiport = 0;
}
else {
    midiport = 0;
}
printf("MIDI output port set to %d.\n", midiport);

// Open the MIDI output port
flag = midiOutOpen(&device, midiport, 0, 0, CALLBACK_NULL);
if (flag != MMSYSERR_NOERROR) {
    printf("Error opening MIDI Output.\n");
    return 1;
}i = 0;
message.data[0] = 0xC0;
message.data[1] = 25;
message.data[2] = 0;
flag = midiOutShortMsg(device, message.word); //program change to steel guitar
if (flag != MMSYSERR_NOERROR) {
    printf("Warning: MIDI Output is not open.\n");
}
while (1){
    if (array[i][1] == 1) { //note on 
        this_works();i++;
    }
    else if (array[i][1] == 0){//note off
        this_also_works();i++;
    }
    else if (array[i][1] == 2){//pitch bend
        while (array[i][1] == 2){
            Sleep(10);
            message.data[0] = 0xE0;
            bend = (uint16_t) array[i][2];
            message.data[1] = bend & mask;
            message.data[2] = (bend & (mask << 7)) >> 7;
            printf("bending %d, %d\n", message.data[1],message.data[2]); 
            flag = midiOutShortMsg(device, message.word);
            if (flag != MMSYSERR_NOERROR) {
                printf("Warning: MIDI Output is not open.\n");
            }i++;
        }
    }
}}

无论如何,printf("bending%d,%d")函数始终将第一个%d打印为0.这是我第一次在midi编程,我以前从未处理过7位值,所以我很困惑,任何帮助都会受到赞赏.

Answer 1

对于弯音消息data1(你的message.data [1])是LSB,data2(message.data [2])是MSB.我不是C开发人员,但这是我在一些伪代码中的做法:

(byte) data2 = pitchbend >> 7
(byte) data1 = pitchbend & 0x7F

用英语讲:

• MSB是:pitchbend bit shift right 7
• LSB是:pitchbend按位AND,掩码为127

作为参考,反过来(例如,如果你在消息中收到它们,则组合两个值来计算弯音)是一个简单的问题:

pitchbend = (data2 * 128) + data1

编辑:我更仔细地阅读你的代码,看起来你已经在做我描述的了.IE:

uint16_t mask = 0x007F;
bend = (uint16_t) array[i][2];

message.data[1] = bend & mask;
message.data[2] = (bend & (mask << 7)) >> 7;

array[i][2]你想发送什么价值？任何128的偶数倍将导致LSB(message.data[1])为零.设备忽略或不使用低字节提供的附加分辨率并不罕见,因此您的样本MIDI数据可能属于这种情况.