Linux ALSA音频库(二) 环境测试+音频合成+语音切换 项目代码分享

1. 环境测试

alsa_test.c

#include <alsa/asoundlib.h>
#include <stdio.h>

//  官方测试代码， 运行后只要有一堆信息打印出来，即说明安装成功了。

int main() 
{
    int val;
 
    printf("ALSA library version: %s
",
                       SND_LIB_VERSION_STR);
 
    printf("
PCM stream types:
");
    for (val = 0; val <= SND_PCM_STREAM_LAST; val++)
            printf(" %s
",
                  snd_pcm_stream_name((snd_pcm_stream_t)val));
 
    printf("
PCM access types:
");
    for (val = 0; val <= SND_PCM_ACCESS_LAST; val++)
    {
            printf(" %s
",
                  snd_pcm_access_name((snd_pcm_access_t)val));
    }
 
    printf("
PCM formats:
");
    for (val = 0; val <= SND_PCM_FORMAT_LAST; val++)
        {
        if (snd_pcm_format_name((snd_pcm_format_t)val)!= NULL)
        {
            printf(" %s (%s)
",
                    snd_pcm_format_name((snd_pcm_format_t)val),
                    snd_pcm_format_description(
                            (snd_pcm_format_t)val));
        }
    }
 
    printf("
PCM subformats:
");
    for (val = 0; val <= SND_PCM_SUBFORMAT_LAST;val++)
    {
            printf(" %s (%s)
",
                  snd_pcm_subformat_name((
                snd_pcm_subformat_t)val),
                  snd_pcm_subformat_description((
                snd_pcm_subformat_t)val));
    }
 
    printf("
PCM states:
");
    for (val = 0; val <= SND_PCM_STATE_LAST; val++)
            printf(" %s
",
                   snd_pcm_state_name((snd_pcm_state_t)val));
 
    return 0;
}

makefile：

.PHONY : rebuild clean


CC:= mips-linux-gnu-gcc
TARGET:= alsa_test.out


OBJS:= alsa_test.o 

INCLUDE += -I/usr/local/open_lib/include

LIBS += -lpthread -L/usr/local/open_lib/lib -lasound


$(TARGET) :$(OBJS)
    $(CC) $(LIBS) $^ -o $@ 


$(OBJS):%.o:%.c
    $(CC) $(INCLUDE) -c $^ -o $@
    echo $(OBJS)


clean:
    $(RM) $(OBJS)
    $(RM) $(TARGET)
    @echo "clean"

rebuild : clean $(TARGET)
    @echo "rebuild"

官方测试代码， 运行后只要有一堆信息打印出来，即说明安装成功了。

2. 音频合成+语音切换 功能使用，单线程，不考虑多线程场景。

alsa_test.c

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <alsa/asoundlib.h>
#include <pthread.h>
#include <unistd.h>
#include <sys/time.h>
static char * name;
struct wav_header
{
    char rld[4]; //riff 标志符号
    int rLen; 
    char wld[4]; //格式类型（wave）
    char fld[4]; //"fmt"

    int fLen; //sizeof(wave format matex)
    
    short wFormatTag; //编码格式
    short wChannels; //声道数
    int nSamplesPersec ; //采样频率
    int nAvgBitsPerSample;//WAVE文件采样大小
    short wBlockAlign; //块对齐
    short wBitsPerSample; //WAVE文件采样大小
    
    char dld[4]; //”data“
    int wSampleLength; //音频数据的大小

} wav_header, wav_header1, wav_header2, wav_header3;
static pthread_mutex_t mutex;   // 等待停止
static pthread_mutex_t mutex_play;  // 开启播放
snd_pcm_t* handle; //PCI设备句柄
static char * path1;
static char * path2;
static pthread_t id;
static char g_stop=0;

static int lock = 0;

int set_pcm_play(const char* path1, const char* path2, const char* path3);
int wait_stop_play(void);


/****   立即关闭播放的方法  ****
        if(handle!=NULL)
        {
          g_stop=1;
          snd_pcm_drop(handle);
        }    
****    ****/

#if 0
int main(void)
{
        system("stty -icanon");

        handle = NULL;    

        set_pcm_play("/etc/door_sound/201.wav", "/etc/door_sound/203.wav", "/etc/door_sound/201.wav");
    printf("-----OVER11111111111111----

");


        set_pcm_play("/etc/door_sound/201.wav", NULL, NULL);
        set_pcm_play("/etc/door_sound/203.wav", NULL, NULL);
        set_pcm_play("/etc/door_sound/201.wav", NULL, NULL);
    printf("-----OVER222222222222-------

");


        sleep(3);

    #if 0  // 存在的问题：set_pcm_play两句话， 前面一句话叫得很快 ， 后面正常  
        set_pcm_play("/etc/door_sound/201.wav", "/etc/door_sound/203.wav", NULL);
        set_pcm_play("/etc/door_sound/201.wav", "/etc/door_sound/203.wav", NULL);

        set_pcm_play(NULL, NULL, "/etc/door_sound/203.wav"); // 这句话没有播放
    printf("-----OVER333333333333-------

");
    #else
        set_pcm_play("/etc/door_sound/201.wav", "/etc/door_sound/203.wav", NULL);
        set_pcm_play("/etc/door_sound/201.wav", "/etc/door_sound/203.wav", NULL);

        set_pcm_play("/etc/door_sound/203.wav", NULL, NULL);
    printf("-----OVER333333333333-------

");
    #endif


        //set_pcm_play("/TG/sound/333.wav", "/TG/sound/333.wav", "/TG/sound/333.wav");
        // set_pcm_play("/TG/sound/1.wav", NULL, NULL);

        return 0;
}

#else


pthread_t Handle_stop_sound_thread;


void *stop_sound_thread(void *arg)
{

    sleep(2);

    if(handle!=NULL)
    {
        printf("即将关闭当前语音流A 
");
        g_stop=1; 
         // snd_pcm_drop(handle); 不要立即关停。  因为这会导致当前正在执行snd_pcm_writei()写入出错。置位一个标志g_stop已经足够。
    }    

    return NULL;
}



/*  ALSA使用教程 
**  Demo演示 
**  LMW  
**  2020 - 07 -xx
**使用了下alsa实现各语音提取合并(语音流A最多由三个wav文件合成) 、以及切换语音播报(关闭当前语音流A转而播报语音流B这样)、
**
**/

int main(void)
{
        system("stty -icanon");

        handle = NULL;    



        //这里新建个线程，延时2秒后关闭当前的语音播放

      if(pthread_create(&Handle_stop_sound_thread, NULL, stop_sound_thread, NULL))
      {
        perror("Create stop_sound_thread Err ");
    }
    else
    {
        pthread_detach(Handle_stop_sound_thread);
    }


        //这里搞个远大于2秒的语音播报
    printf("-准备播报语音流A..
");
        set_pcm_play("/etc/door_sound/254.wav", "/etc/door_sound/203.wav", "/etc/door_sound/201.wav");
    printf("-已关闭(中止)当前语音流A！

");

        //sleep(3);
    printf("-准备播报语音流B..
");
    set_pcm_play("/etc/door_sound/254.wav", "/etc/door_sound/203.wav", "/etc/door_sound/201.wav");
    printf("-语音流B顺利执行完毕！

");


        //sleep(3);
    printf("-准备播报语音流C..
");
    set_pcm_play("/etc/door_sound/254.wav", "/etc/door_sound/254.wav", "/etc/door_sound/254.wav");
    printf("-语音流C顺利执行完毕！

");


        return 0;
}

#endif


int para_common_set(int channels, int frequency, 
          int bit, int datablock, snd_pcm_uframes_t *pframes)
{
        int size = 0, dir=0;;
      snd_pcm_hw_params_t* params;   //硬件信息和PCM流配置
    unsigned int val;
        int ret;
        // 如果要做多线程处理，这里应该维护一个计数器cnt，使用mutex来保护该计数器
        // 打开音频设备时，只有第一次打开才执行snd_pcm_open，以后则只是cnt++
        // 同理，关闭设备时，执行计数器--操作，直到计数器减为0,才执行snd_pcm_close真正将设备关闭
        
        //因为我的程序并不涉及多线程操作音频设备，所以不做上述处理
        //单线程处理，这样够了：使用lock，确保该函数多次调用，只打开一次设备。
        if(!lock) 
        {
        

            lock = 1; //snd_pcm_close()内会清零该lock，以便下次再打开设备

          ret= snd_pcm_open(&handle, "default",    
                            SND_PCM_STREAM_PLAYBACK, 0);
            if(ret<0)
            {
                    printf("open PCM device failed
");
                    
            }

        }

            snd_pcm_hw_params_alloca(&params); //分配params结构体


            ret= snd_pcm_hw_params_any(handle, params);//初始化params
            if(ret<0)
            {
                    printf("snd_pcm_hw_params_any err
");
                    
            }

            ret= snd_pcm_hw_params_set_access(handle, params, 
                            SND_PCM_ACCESS_RW_INTERLEAVED); //初始化访问权限
            if(ret<0)
            {
                    printf("sed_pcm_hw_set_access err
");
                    
            }

        
        //采样位数
        switch(bit/8)
        {
                case 1:snd_pcm_hw_params_set_format(handle, params,
                          SND_PCM_FORMAT_U8);
                        break ;
                case 2:snd_pcm_hw_params_set_format(handle, params,
                          SND_PCM_FORMAT_S16_LE);
                        break ;
                case 3:snd_pcm_hw_params_set_format(handle, params,
                          SND_PCM_FORMAT_S24_LE);
                        break ;
 
                default:
                        printf("default 
");
                    break;

        }


      ret= snd_pcm_hw_params_set_channels(handle, params,    
                     channels); //设置声道,1表示单声>道，2表示立体声
        if(ret<0)
        {
                printf("snd_pcm_hw_params_set_channels err
");
                
        }

        val = frequency;

        ret= snd_pcm_hw_params_set_rate_near(handle, params,   
                    &val, &dir); //设置>频率
        if(ret<0)
        {
                printf("snd_pcm_hw_params_set_rate_near err
");
                
        }

        ret = snd_pcm_hw_params(handle, params);
        if(ret<0)
        {
              printf("snd_pcm_hw_params err 
");
            
        }

        ret=snd_pcm_hw_params_get_period_size(params, pframes, 
                   &dir); /*获取周期长度*/
        if(ret<0)
        {
                printf("snd_pcm_hw_params_get_period_size err
");
                
        }

        // 一个数据块，一个数据块，依次读取。
        size = (*pframes) * datablock; /*代表数据块长度*/

        printf("--malloc(size), size = %d 
",size);

        return size;
}

#define max_num  5

struct wav_file_info {

    FILE* fp;

    int size;

    snd_pcm_uframes_t frames;


    short channels;
    int frequency;
    short bit;
    short datablock; 


}wavinfo[max_num];


/*
        path1 = malloc(50);
        path2 = malloc(50);

        sprintf(path1,"/TG/sound/%d.wav", 1);
        sprintf(path2,"/TG/sound/%d.wav", 2);

*/


//void Get_fp_and_wavheader(const char* path, FILE **pfp, struct wav_header* phead_info)
FILE * Get_fp_and_wavheader(const char* path, struct wav_header* phead_info)
{
                if(NULL != path) {
                
                printf("path = %s 
", path);

                FILE *fp=fopen(path,"rb");

                if(NULL==fp)
                {
                    printf("open wav failed:
");
                    return NULL;
                }

                printf("fp = %p 
", fp);
                fread(phead_info, 1, sizeof(struct wav_header),fp);

                return fp;
                /*  
        printf("文件大小rLen:   %d
", phead_info->rLen);
        printf("声道数：        %d
", phead_info->wChannels);
        printf("采样频率：      %d
", phead_info->nSamplesPersec);
        printf("采样的位数:     %d
", phead_info->wBitsPerSample);
        printf("wSampleLength=%d
", phead_info->wSampleLength);
        */

            }
}


// 对fopen的理解：
// 即使3次fopen同一个文件，也不要紧，会返回3个不同的fp，但是指向同一个文件.
int set_pcm_play(const char* path1, const char* path2, const char* path3)
{
        int ret;
        unsigned int size = 0;
                unsigned int size1 = 0, size2 = 0, size3 = 0;
                int num=0;
        
        int dir=0;
        snd_pcm_uframes_t frames, frames1, frames2, frames3;
        char *buffer;

        int channels;
        int frequency;
        int bit;
        int datablock;
                
        
        FILE *fp1 = NULL, *fp2 = NULL, *fp3 = NULL;  
                FILE* fpCur[max_num] = {0};

                const char* file_paths[3] = {0};

                file_paths[0] = path1;
                file_paths[1] = path2;
                file_paths[2] = path3;            



                if(NULL != path3) {

                    fp3 = Get_fp_and_wavheader(path3, &wav_header3);

                    if(fp3 != NULL) {

          channels = wav_header3.wChannels;
          frequency= wav_header3.nSamplesPersec;
          bit      = wav_header3.wBitsPerSample;
          datablock= wav_header3.wBlockAlign; 

                    #if 0 
                        printf("fp3 datablock:   %d
",   datablock);
                        printf("声道数：        %d
", channels);
                        printf("采样频率：      %d
", frequency);
                        printf("采样的位数:     %d
", bit);
                        printf("wSampleLength=%d


", wav_header3.wSampleLength);
                    #endif


                    wavinfo[2].channels = channels;
                    wavinfo[2].frequency = frequency;
                    wavinfo[2].bit = bit;
                    wavinfo[2].datablock = datablock;

                    size3 = para_common_set(channels, frequency, bit, datablock, &frames3);
                    //获取各自的rames。
                    wavinfo[2].size = size3; 
                    wavinfo[2].frames = frames3;
                    }
                }


                if(NULL != path2) {
                    
                    fp2 = Get_fp_and_wavheader(path2, &wav_header2);

                    if(fp2 != NULL) {

                        channels = wav_header2.wChannels;
                        frequency= wav_header2.nSamplesPersec;
                        bit      = wav_header2.wBitsPerSample;
                        datablock= wav_header2.wBlockAlign; 

                    #if 0 
                        printf("fp2 datablock:   %d
",   datablock);
                        printf("声道数：        %d
", channels);
                        printf("采样频率：      %d
", frequency);
                        printf("采样的位数:     %d
", bit);
                        printf("wSampleLength=%d


", wav_header2.wSampleLength);
                    #endif

                    wavinfo[1].channels = channels;
                    wavinfo[1].frequency = frequency;
                    wavinfo[1].bit = bit;
                    wavinfo[1].datablock = datablock;

                        size2 = para_common_set(channels, frequency, bit, datablock, &frames2);
                        //获取各自的rames。
                        wavinfo[1].size = size2; 
                        wavinfo[1].frames = frames2;
                    }
                }


                if(NULL != path1) {

        #if 1
          // 对fopen的理解：
                    // 即使3次fopen同一个文件，也不要紧，会返回3个不同的fp，但是指向同一个文件.
                  fp1 = Get_fp_and_wavheader(path1, &wav_header1);
        #else
        char *path111 = malloc(50);
                 sprintf(path111,"/TG/sound/%d.wav", 1);
                fp1=fopen(path111,"rb");
        if(fp1==NULL)
        {
          printf("open wav1 failed:
");
          return -1;
        }

        fread(&wav_header1,1,sizeof(wav_header1),fp1);
        #endif


        // 实际上给入的每个音频文件的采样率啥的都是一样的，但是每个音频文件的大小可能不一样，
                // 所以需要单独针对每个音频文件设置这里，获取各自的frames。
                    if(fp1 != NULL) {

                        printf("fp1 = %p 
", fp1);
                        channels = wav_header1.wChannels;
                        frequency= wav_header1.nSamplesPersec;
                        bit      = wav_header1.wBitsPerSample;
                        datablock= wav_header1.wBlockAlign; 

                    #if 0 
                        printf("fp1 datablock:   %d
",   datablock);
                        printf("声道数：        %d
", channels);
                        printf("采样频率：      %d
", frequency);
                        printf("采样的位数:     %d
", bit);
                        printf("wSampleLength=%d


", wav_header1.wSampleLength);
                    #endif

                    wavinfo[0].channels = channels;
                    wavinfo[0].frequency = frequency;
                    wavinfo[0].bit = bit;
                    wavinfo[0].datablock = datablock;

                        size1 = para_common_set(channels, frequency, bit, datablock, &frames1);
                        //获取各自的rames。
                        wavinfo[0].size = size1; 
                        wavinfo[0].frames = frames1;
                    //    printf("size1 = %d 
",size1);
                    //    printf("wavinfo[0].size = %d 
", wavinfo[0].size);

                    }

                }


                wavinfo[0].fp = fp1;
                wavinfo[1].fp = fp2;
                wavinfo[2].fp = fp3;

        #if 0    
                printf("wavinfo[0].fp = %d 
", wavinfo[0].fp);
                printf("fp1 = %d 
", fp1);                
        
        #endif

                if(size1 > size2) {
                    size = size1;
                }
                else {
                    size = size2;
                }
        
                if(size > size3) {
                
                }
                else {
                    size = size3;
                }

                printf("size = %d 
", size);

   
                buffer = (char*)malloc(size);

        #if 1
        // fseek(fp1, 58, SEEK_SET);

                //printf("wavinfo[0].fp = %d 
", wavinfo[0].fp);
                //printf("fp1 = %d 
", fp1);    

                if(wavinfo[0].fp) {                
              fseek(wavinfo[0].fp, 44, SEEK_SET); //定位歌曲到数据区
                }
                if(wavinfo[1].fp) {               
                    printf("--2 
");
              fseek(wavinfo[1].fp, 44, SEEK_SET); //定位歌曲到数据区
                }
                if(wavinfo[2].fp) {                
                    printf("--3 
");
              fseek(wavinfo[2].fp, 44, SEEK_SET); //定位歌曲到数据区
                }
        #endif

                int index = 0;
            //    printf("-wavinfo[0].fp = %d 
", wavinfo[0].fp);
            //    printf("-wavinfo[1].fp = %d 
", wavinfo[1].fp);
            //    printf("-wavinfo[2].fp = %d 
", wavinfo[2].fp);

          while ((g_stop == 0) && (wavinfo[index].fp))
        {
                                num++;

                memset(buffer, 0x00, size);
                                
    
                                if(wavinfo[index].fp) {

              
                                     // 一个数据块，一个数据块，依次读取。
                                    ret = fread(buffer, 1, wavinfo[index].size, wavinfo[index].fp);
                                    if(ret == 0) {

                                            printf("曲目读取 end
");
 
                      fclose(wavinfo[index].fp);
                                            wavinfo[index].fp = NULL;

                                            index++;

                                            continue;  
                                            //printf("--not reached here 
");
                                            
                                    }
                                    else if (ret != size) {
                                            printf("left: read %d bytes
", ret);
                                    }

                                    //printf("-play %d
", ret);

                                    // 写音频数据到PCM设备 
                                    //struct timeval time1,time2;
                                    //gettimeofday(&time1,NULL); 


                                    ret = snd_pcm_writei(handle, buffer, wavinfo[index].frames);
                                    //snd_pcm_prepare(handle);
                                    //gettimeofday(&time2,NULL);
                                    //printf("time=%d
",            
                                        (time2.tv_sec-time1.tv_sec)*1000000+time2.tv_usec-time1.tv_usec);
                                    if (ret == -EPIPE)
                                    {
                                        printf("underrun occurred
");
                                        //完成硬件参数设置，使设备准备好 
                                        snd_pcm_prepare(handle); // 继续
                                    }
                                    else if (ret < 0)
                                    {
                                            printf("error from writei: %s
",snd_strerror(ret));
                                    }
                                    else if (ret != (int)wavinfo[index].frames) 
                                    {
                                            printf("short write, write %d frames
", ret);
                                    }

                                }


          }

                snd_pcm_drain(handle); // 清空pcm内部音频数据流缓存
                snd_pcm_drop(handle);  // 暂停

                int i=0;
                for(i=0; i<max_num; i++)
                {

                  if(wavinfo[i].fp)
                        fclose(wavinfo[i].fp);
                }

                lock = 0;
                snd_pcm_close(handle);
                free(buffer);
                handle = NULL;
                g_stop=0;
        return 0;

}

makefile：

.PHONY : rebuild clean


CC:= mips-linux-gnu-gcc
TARGET:= alsa_test.out


OBJS:= alsa_test.o 

# 老旧知识点： -I -L -l 详解  
#-I /home/hello/include   表示将/home/hello/include目录作为第一个寻找头文件的目录
#-L /home/hello/lib   表示将/home/hello/lib目录作为第一个寻找库文件的目录
#-lworld      表示在上面的lib的路径中寻找libworld.so动态库文件（如果gcc编译选项中加入了“-static”表示寻找libworld.a静态库文件）

INCLUDE += -I /usr/local/open_lib/include

LIBS += -lpthread -L/usr/local/open_lib/lib -lasound


$(TARGET) :$(OBJS)
    $(CC) $(LIBS) $^ -o $@ 


$(OBJS):%.o:%.c
    $(CC) $(INCLUDE) -c $^ -o $@
    echo $(OBJS)


clean:
    $(RM) $(OBJS)
    $(RM) $(TARGET)
    @echo "clean"

rebuild : clean $(TARGET)
    @echo "rebuild"

本例子在项目中，功能使用良好。

.