linux alsa编程源码集合

linux 下 列出所有alsa设备代码

static void device_list(void)
{
    snd_ctl_t *handle;
    int card, err, dev, idx;
    snd_ctl_card_info_t *info;
    snd_pcm_info_t *pcminfo;
    snd_ctl_card_info_alloca(&info);
    snd_pcm_info_alloca(&pcminfo);

    card = -1;
    if (snd_card_next(&card) < 0 || card < 0) {
        error(_("no soundcards found..."));
        return;
    }
    printf(_("**** List of %s Hardware Devices ****\n"),
           snd_pcm_stream_name(stream));
    while (card >= 0) {
        char name[32];
        sprintf(name, "hw:%d", card);
        if ((err = snd_ctl_open(&handle, name, 0)) < 0) {
            error("control open (%i): %s", card, snd_strerror(err));
            goto next_card;
        }
        if ((err = snd_ctl_card_info(handle, info)) < 0) {
            error("control hardware info (%i): %s", card, snd_strerror(err));
            snd_ctl_close(handle);
            goto next_card;
        }
        dev = -1;
        while (1) {
            unsigned int count;
            if (snd_ctl_pcm_next_device(handle, &dev)<0)
                error("snd_ctl_pcm_next_device");
            if (dev < 0)
                break;
            snd_pcm_info_set_device(pcminfo, dev);
            snd_pcm_info_set_subdevice(pcminfo, 0);
            snd_pcm_info_set_stream(pcminfo, stream);
            if ((err = snd_ctl_pcm_info(handle, pcminfo)) < 0) {
                if (err != -ENOENT)
                    error("control digital audio info (%i): %s", card, snd_strerror(err));
                continue;
            }
            printf(_("card %i: %s [%s], device %i: %s [%s]\n"),
                card, snd_ctl_card_info_get_id(info), snd_ctl_card_info_get_name(info),
                dev,
                snd_pcm_info_get_id(pcminfo),
                snd_pcm_info_get_name(pcminfo));
            count = snd_pcm_info_get_subdevices_count(pcminfo);
            printf( _("  Subdevices: %i/%i\n"),
                snd_pcm_info_get_subdevices_avail(pcminfo), count);
            for (idx = 0; idx < (int)count; idx++) {
                snd_pcm_info_set_subdevice(pcminfo, idx);
                if ((err = snd_ctl_pcm_info(handle, pcminfo)) < 0) {
                    error("control digital audio playback info (%i): %s", card, snd_strerror(err));
                } else {
                    printf(_("  Subdevice #%i: %s\n"),
                        idx, snd_pcm_info_get_subdevice_name(pcminfo));
                }
            }
        }
        snd_ctl_close(handle);
    next_card:
        if (snd_card_next(&card) < 0) {
            error("snd_card_next");
            break;
        }
    }
}

linux下ALSA播放声音的源程序

#include
/* Use the newer ALSA API */
#define ALSA_PCM_NEW_HW_PARAMS_API

#include

int main()
{
    long loops;
    int rc;
    int size;
    snd_pcm_t *handle;
    snd_pcm_hw_params_t *params;
    unsigned int val;
    int dir;
    snd_pcm_uframes_t frames;
    snd_pcm_uframes_t periodsize;
    char *buffer;
    FILE *fp = fopen("play.wav", "rb");
    if(fp == NULL)
    return 0;
    fseek(fp, 100, SEEK_SET);
    /* Open PCM device for playback. */
    rc = snd_pcm_open(&handle, "default",
                    SND_PCM_STREAM_PLAYBACK, 0);//SND_PCM_NONBLOCK);
    if (rc < 0) {
    fprintf(stderr,
            "unable to open pcm device: %s\n",
            snd_strerror(rc));
    exit(1);
    }

    /* Allocate a hardware parameters object. */
    snd_pcm_hw_params_alloca(¶ms);

    /* Fill it in with default values. */
    snd_pcm_hw_params_any(handle, params);

    /* Set the desired hardware parameters. */

    /* Interleaved mode */
    snd_pcm_hw_params_set_access(handle, params,
                      SND_PCM_ACCESS_RW_INTERLEAVED);

    /* Signed 16-bit little-endian format */
    snd_pcm_hw_params_set_format(handle, params,
                              SND_PCM_FORMAT_S16_LE);

    /* Two channels (stereo) */
    snd_pcm_hw_params_set_channels(handle, params, 1);

    /* 44100 bits/second sampling rate (CD quality) */
    val = 8000;
    snd_pcm_hw_params_set_rate_near(handle, params,
                                  &val, &dir);

    /* Set period size to 32 frames. */
    frames = 32;
    periodsize = frames * 2;
    rc = snd_pcm_hw_params_set_buffer_size_near(handle, params, &periodsize);
    if (rc < 0)
    {
         printf("Unable to set buffer size %li : %s\n", frames * 2, snd_strerror(rc));
        
    }
          periodsize /= 2;
    rc = snd_pcm_hw_params_set_period_size_near(handle, params, &periodsize, 0);
    if (rc < 0)
    {
        printf("Unable to set period size %li : %s\n", periodsize,  snd_strerror(rc));
    }
    
    /* Write the parameters to the driver */
    rc = snd_pcm_hw_params(handle, params);
    if (rc < 0) {
    fprintf(stderr,
            "unable to set hw parameters: %s\n",
            snd_strerror(rc));
    }

    /* Use a buffer large enough to hold one period */
    snd_pcm_hw_params_get_period_size(params, &frames, &dir);
                                
    size = frames * 2; /* 2 bytes/sample, 2 channels */
    buffer = (char *) malloc(size);
    fprintf(stderr,
            "size = %d\n",
            size);
    /* We want to loop for 5 seconds */
    //snd_pcm_hw_params_get_period_time(params,
    //                                &val, &dir);
    //snd_pcm_start(handle);
    while (1)
    {
        rc = fread(buffer, 1, size, fp);
        if(rc == 0)
        {
              fprintf(stderr, "end of file on input\n");
              break;
        }
        else if (rc != size)
        {
        }

        while(rc = snd_pcm_writei(handle, buffer, frames)<0)
        {
            usleep(2000);
            if (rc == -EPIPE)
            {
                  /* EPIPE means underrun */
                  fprintf(stderr, "underrun occurred\n");
                  snd_pcm_prepare(handle);
            }
            else if (rc < 0)
            {
                  fprintf(stderr,
                      "error from writei: %s\n",
                      snd_strerror(rc));
            }  
        }
        //snd_pcm_drain(handle);
        //usleep(7000);
        //printf("#\n");
    }
    snd_pcm_drain(handle);
    snd_pcm_close(handle);
    free(buffer);
    fclose(fp);
    return 0;
}

linux下ALSA录制声音的源程序

/* Use the newer ALSA API */
#define ALSA_PCM_NEW_HW_PARAMS_API

#include

/* this buffer holds the digitized audio */
//unsigned char buf[LENGTH*RATE*SIZE*CHANNELS/8];
typedef unsigned char   BYTE;
typedef unsigned short  WORD;
typedef unsigned int  DWORD;
typedef unsigned int  FOURCC;    /* a four character code */

/* flags for 'wFormatTag' field of WAVEFORMAT */
#define WAVE_FORMAT_PCM 1

/* MMIO macros */
#define mmioFOURCC(ch0, ch1, ch2, ch3) \
  ((DWORD)(BYTE)(ch0) | ((DWORD)(BYTE)(ch1) << 8) | \
  ((DWORD)(BYTE)(ch2) << 16) | ((DWORD)(BYTE)(ch3) << 24))

#define FOURCC_RIFF    mmioFOURCC ('R', 'I', 'F', 'F')
#define FOURCC_LIST    mmioFOURCC ('L', 'I', 'S', 'T')
#define FOURCC_WAVE    mmioFOURCC ('W', 'A', 'V', 'E')
#define FOURCC_FMT    mmioFOURCC ('f', 'm', 't', ' ')
#define FOURCC_DATA    mmioFOURCC ('d', 'a', 't', 'a')

typedef struct CHUNKHDR {
    FOURCC ckid;        /* chunk ID */
    DWORD dwSize;             /* chunk size */
} CHUNKHDR;

/* simplified Header for standard WAV files */
typedef struct WAVEHDR {
    CHUNKHDR chkRiff;
    FOURCC fccWave;
    CHUNKHDR chkFmt;
    WORD wFormatTag;       /* format type */
    WORD nChannels;       /* number of channels (i.e. mono, stereo, etc.) */
    DWORD nSamplesPerSec;  /* sample rate */
    DWORD nAvgBytesPerSec; /* for buffer estimation */
    WORD nBlockAlign;       /* block size of data */
    WORD wBitsPerSample;
    CHUNKHDR chkData;
} WAVEHDR;

#if BYTE_ORDER == BIG_ENDIAN
# define cpu_to_le32(x) SWAP4((x))
# define cpu_to_le16(x) SWAP2((x))
# define le32_to_cpu(x) SWAP4((x))
# define le16_to_cpu(x) SWAP2((x))
#else
# define cpu_to_le32(x) (x)
# define cpu_to_le16(x) (x)
# define le32_to_cpu(x) (x)
# define le16_to_cpu(x) (x)
#endif

static void wav_init_header(WAVEHDR *fileheader)
{
    /* stolen from cdda2wav */
    int nBitsPerSample = 16;
    int channels       = 1;
    int rate           = 8000;

    unsigned long nBlockAlign = channels * ((nBitsPerSample + 7) / 8);
    unsigned long nAvgBytesPerSec = nBlockAlign * rate;
    unsigned long temp = /* data length */ 0 +
    sizeof(WAVEHDR) - sizeof(CHUNKHDR);

    fileheader->chkRiff.ckid    = cpu_to_le32(FOURCC_RIFF);
    fileheader->fccWave         = cpu_to_le32(FOURCC_WAVE);
    fileheader->chkFmt.ckid     = cpu_to_le32(FOURCC_FMT);
    fileheader->chkFmt.dwSize   = cpu_to_le32(16);
    fileheader->wFormatTag      = cpu_to_le16(WAVE_FORMAT_PCM);
    fileheader->nChannels       = cpu_to_le16(channels);
    fileheader->nSamplesPerSec  = cpu_to_le32(rate);
    fileheader->nAvgBytesPerSec = cpu_to_le32(nAvgBytesPerSec);
    fileheader->nBlockAlign     = cpu_to_le16(nBlockAlign);
    fileheader->wBitsPerSample  = cpu_to_le16(nBitsPerSample);
    fileheader->chkData.ckid    = cpu_to_le32(FOURCC_DATA);
    fileheader->chkRiff.dwSize  = cpu_to_le32(temp);
    fileheader->chkData.dwSize  = cpu_to_le32(0 /* data length */);
}

static void wav_start_write(FILE* fd, WAVEHDR *fileheader)
{
    wav_init_header(fileheader);
    fwrite(fileheader,1, sizeof(WAVEHDR), fd);
}

static void wav_stop_write(FILE* fd, WAVEHDR *fileheader, int wav_size)
{
    unsigned long temp = wav_size + sizeof(WAVEHDR) - sizeof(CHUNKHDR);

    fileheader->chkRiff.dwSize = cpu_to_le32(temp);
    fileheader->chkData.dwSize = cpu_to_le32(wav_size);
    fseek(fd,0,SEEK_SET);
       fwrite(fileheader,1, sizeof(WAVEHDR), fd);
}

int main()
{
    long loops;
    int rc;
    int size;
    snd_pcm_t *rec_handle;
    snd_pcm_hw_params_t *rec_params;
    unsigned int val;
    int dir;
    snd_pcm_uframes_t frames;
    char *buffer;
    WAVEHDR wavheader;
    int total_len = 0;
    FILE *fp_rec = fopen("rec.wav", "wb");
    if(fp_rec==NULL)
    {
        return 0;
    }
    wav_start_write(fp_rec, &wavheader);
    /* Open PCM device for recording (capture). */
    rc = snd_pcm_open(&rec_handle, "default",
                        SND_PCM_STREAM_CAPTURE, 0);
    if (rc < 0) {
        fprintf(stderr,
                "unable to open pcm device: %s\n",
                snd_strerror(rc));
        exit(1);
    }

    /* Allocate a hardware parameters object. */
    snd_pcm_hw_params_alloca(&rec_params);

    /* Fill it in with default values. */
    snd_pcm_hw_params_any(rec_handle, rec_params);

    /* Set the desired hardware parameters. */

    /* Interleaved mode */
    snd_pcm_hw_params_set_access(rec_handle, rec_params,
                          SND_PCM_ACCESS_RW_INTERLEAVED);

    /* Signed 16-bit little-endian format */
    snd_pcm_hw_params_set_format(rec_handle, rec_params,
                                  SND_PCM_FORMAT_S16_LE);

    /* Two channels (stereo) */
    snd_pcm_hw_params_set_channels(rec_handle, rec_params, 1);

    /* 44100 bits/second sampling rate (CD quality) */
    val = 8000;
    snd_pcm_hw_params_set_rate_near(rec_handle, rec_params,
                                      &val, &dir);

    /* Set period size to 32 frames. */
    frames = 32;
    snd_pcm_hw_params_set_period_size_near(rec_handle,
                                  rec_params, &frames, &dir);

    /* Write the parameters to the driver */
    rc = snd_pcm_hw_params(rec_handle, rec_params);
    if (rc < 0)
    {
        fprintf(stderr,
                "unable to set hw parameters: %s\n",
                snd_strerror(rc));
        exit(1);
    }

    /* Use a buffer large enough to hold one period */
    snd_pcm_hw_params_get_period_size(rec_params,  &frames, &dir);
    size = frames * 2; /* 2 bytes/sample, 2 channels */
    buffer = (char *) malloc(size);

    /* We want to loop for 5 seconds */
    snd_pcm_hw_params_get_period_time(rec_params, &val, &dir);
    loops = 2000;

    while (loops-- > 0)
    {
        rc = snd_pcm_readi(rec_handle, buffer, frames);

 if (rc == -EPIPE)
        {
          /* EPIPE means overrun */
          fprintf(stderr, "overrun occurred\n");
          snd_pcm_prepare(rec_handle);
        }
        else if (rc < 0)
        {
          fprintf(stderr, "error from read: %s\n", snd_strerror(rc));
        }
        else if (rc != (int)frames)
        {
          fprintf(stderr, "short read, read %d frames\n", rc);
        }
        rc = fwrite(buffer, 1, size, fp_rec);
        total_len += size;
        printf("#\n");
        if (rc != size)
          fprintf(stderr,"short write: wrote %d bytes\n", rc);
    }
    wav_stop_write(fp_rec, &wavheader, total_len);
    snd_pcm_drain(rec_handle);
    snd_pcm_close(rec_handle);
    free(buffer);
    fclose(fp_rec);
    return 0;
}