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我必须在大学写一个简单的合成器，它使用 sdl_mixer 来生成正弦波。我从老师那里得到了一个代码，它可以在 Windows 上正常工作，但在 ubuntu 中它会因分段错误而退出。我安装了 sdl_mixer1.2-dev 和 sdl1.2-dev 软件包。我尝试了一个使用 sdl_audio 生成音调的代码。它工作得很好，但我听说对于多声道播放，sdl_mixer 是解决方案。代码的 getch() 部分运行良好，问题出在声音管理器部分。

有人可以帮我解决这个问题吗？

这是我的代码：

#include <iostream>
#include <termios.h>
#include <stdio.h>
#include<cmath>
#include <SDL/SDL_mixer.h>
#include<vector>

using namespace std;


class SoundManager
{
    int channelnum;
    vector<Mix_Chunk*> chunks;
public:
    void init()
    {
        if (Mix_OpenAudio(48000,AUDIO_S16, 2, 1024) == -1)
        {
            cerr << "audio hiba" << endl;
            exit(1);
        }
    }
    SoundManager(int asked_channelnum=64)
    {
        channelnum = Mix_AllocateChannels(asked_channelnum);
        chunks.assign(channelnum, (Mix_Chunk*)0);
    }
    int get_channelnum() const
    {
        return channelnum;
    }
    void play_stereo(const vector<short int>& v, int volume=128)
    {
        const short int *p = &(v[0]);
//        short int * p = new short int[v.size()];
//        for (size_t i=0;i<v.size();i++) {
//            p[i]=v[i];
//        }
        Mix_Chunk * ownsample = new Mix_Chunk;
        ownsample->alen = v.size()*2;
        ownsample->abuf = (Uint8*)p;
        ownsample->allocated = 1;
        ownsample->volume = volume;
        int playchannel = Mix_PlayChannel(-1, ownsample, 0);
        if (playchannel != -1 && chunks[playchannel])
        {
            delete[] chunks[playchannel]->abuf;
            Mix_FreeChunk(chunks[playchannel]);
        }
        if (playchannel != -1)
            chunks[playchannel] = ownsample;
    }
};

Mix_Chunk *ownsample = 0;
Mix_Chunk *samples = 0;

void hang()
{
    if (Mix_OpenAudio(48000,AUDIO_S16, 2, 1024) == -1)
    {
        cerr << "audio hiba" << endl;
        exit(1);
    }
    vector<short> s(48000*2,0);
    for (int i=0; i<s.size()/2; i++)
    {
        s[i*2] = sin(i/10.0+i*i/10000.0)*32000*(1/sqrt(i/100.0));
        s[i*2+1] = sin(i/10.0)*32000*(1/sqrt(i/100.0));
    }
    samples = Mix_LoadWAV("ding.wav");
    ownsample = new Mix_Chunk;
    ownsample->alen = s.size()*2;
    ownsample->abuf =(unsigned char*) &(s[0]);
    ownsample->allocated = 0;
    ownsample->volume = 128;
    cout << samples->alen << endl;
    if (!samples)
    {
        cerr << "wav 'ding.wav' open error" << endl;
        exit(1);
    }
    int channelnum = Mix_AllocateChannels(64);

    if (channelnum != 64)
    {
        cerr << "warning: not as many channels are reserved as attended"<<endl;
    }
    if (Mix_PlayChannel(-1, ownsample, 0)==-1 )
    {
        cerr << "error on play" << endl;
    }
//    if (Mix_PlayChannel(-1, samples, 0)==-1 ) {
//        cerr << "error on play" << endl;
//    }

}



void pitty(SoundManager &sm)
{
    vector<short> s(48000*2,0);
    for (int i=0; i<s.size()/2; i++)
    {
        s[i*2] = sin(i/10.0+i*i/10000.0)*32000*(1/sqrt(i/100.0));

        s[i*2+1] = sin(i/10.0)*32000*(1/sqrt(i/100.0));
    }
    sm.play_stereo(s);
}


static struct termios old, New;

/* Initialize New terminal i/o settings */
void initTermios(int echo)
{
    tcgetattr(0, &old); /* grab old terminal i/o settings */
    New = old; /* make New settings same as old settings */
    New.c_lflag &= ~ICANON; /* disable buffered i/o */
    New.c_lflag &= echo ? ECHO : ~ECHO; /* set echo mode */
    tcsetattr(0, TCSANOW, &New); /* use these New terminal i/o settings now */
}

/* Restore old terminal i/o settings */
void resetTermios(void)
{
    tcsetattr(0, TCSANOW, &old);
}

/* Read 1 character - echo defines echo mode */
char getch_(int echo)
{
    int ch;
    initTermios(echo);
    ch = getchar();
    resetTermios();
    return ch;
}

/* Read 1 character without echo */
int getch(void)
{
    return getch_(o);
}

/* Read 1 character with echo */
int getche(void)
{
    return getch_(1);
}





int main(void)
{
    SoundManager sm(16);
    sm.init();
    vector<short> s(48000*2,0);
    for (int i=0; i<s.size()/2; i++)
    {
        s[i*2] = sin(i/10.0+i*i/10000.0)*32000*(1/sqrt(i/100.0));

        s[i*2+1] = sin(i/10.0)*32000*(1/sqrt(i/100.0));
    }

    int c;
    while (1)
    {
        c = getch();
        cout <<"keycode:\n";
        cout <<c;
        sm.play_stereo(s);
    }
    return 0;
}

提前谢谢你的帮助。

问候，伊斯特万·维莱吉

4

2 回答 2

0

这看起来绝对，完全是假的：

void play_stereo(const vector<short int>& v, int volume=128)
{
    const short int *p = &(v[0]);

    //...

    ownsample->abuf = (Uint8*)p;

    //...
        delete[] chunks[playchannel]->abuf;

是的，我意识到chunks[playchannel]还ownsample 没有，但你确实放入ownsample了chunks队列，所以最终你会回来尝试delete[]a 的内部数组存储vector<short int>。

这很糟糕。

这个注释掉的代码实际上似乎是正确的东西来代替const short int *p = &(v[0])：

//        short int * p = new short int[v.size()];
//        for (size_t i=0;i<v.size();i++) {
//            p[i]=v[i];
//        }
于 2013-12-01T23:18:07.060 回答
0

(1) 如果您遇到分段错误，您可以重新编译带有调试符号的代码（如果您使用的是 g++ 或 clang++）；使用-g3。

(2) 使用调试器运行程序并获取代码分段错误所在的堆栈跟踪（使用 gdb）。

于 2013-12-01T18:18:14.210 回答