linuxALSA应用编程笔记

        ALSA是linux的主流音频软件架构,包括驱动和应用程序两个部分,根据官网和自己查找的资料总结了一些知识,更详细的资料参考alsa官网。

        alsa c开发参考文档地址:ALSA project - the C library reference: Index, Preamble and License

ALSA 官方 Examples主要有:

  • /test/pcm.c
  • /test/pcm_min.c
  • /test/latency.c
  • /test/rawmidi.c
  • /test/timer.c

在使用例子之前需要安装ALSA库,Ubuntu开发安装方法:

  1. 进入ALSA主页:AlsaProject Download alsa-lib库解压出来
  2. 编译alsa-lib库 生成makefile ./configure,编译文件 make
  3. 安装alsa库 sudo make install (注意使用sudo超级权限)
  4. 编译例子使用(gcc -o 文件名 文件名.c -lasound)命令

linuxALSA应用编程笔记_第1张图片

ALSA在linux中的架构图 

示例1 pcm.c创建一个正弦波输入到声卡里面,提供了几种写的方式

struct transfer_method {
    const char *name;
    snd_pcm_access_t access;
    int (*transfer_loop)(snd_pcm_t *handle,
                 signed short *samples,
                 snd_pcm_channel_area_t *areas);
};
 
static struct transfer_method transfer_methods[] = {
    { "write", SND_PCM_ACCESS_RW_INTERLEAVED, write_loop },
    { "write_and_poll", SND_PCM_ACCESS_RW_INTERLEAVED, write_and_poll_loop },
    { "async", SND_PCM_ACCESS_RW_INTERLEAVED, async_loop },
    { "async_direct", SND_PCM_ACCESS_MMAP_INTERLEAVED, async_direct_loop },
    { "direct_interleaved", SND_PCM_ACCESS_MMAP_INTERLEAVED, direct_loop },
    { "direct_noninterleaved", SND_PCM_ACCESS_MMAP_NONINTERLEAVED, direct_loop },
    { "direct_write", SND_PCM_ACCESS_MMAP_INTERLEAVED, direct_write_loop },
    { NULL, SND_PCM_ACCESS_RW_INTERLEAVED, NULL }
};

        这个文件提供了几个具体写音频数据格式的函数,播放音乐可以使用这些接口具体参考pcm.c文件

播放声音参考pcm_min.c文件:

/*
 *  This extra small demo sends a random samples to your speakers.
 */
 
#include "../include/asoundlib.h"
 
static char *device = "default";            /* playback device */
unsigned char buffer[16*1024];              /* some random data */
 
int main(void)
{
    int err;
    unsigned int i;
    snd_pcm_t *handle;
    snd_pcm_sframes_t frames;
 
    for (i = 0; i < sizeof(buffer); i++)
        buffer[i] = random() & 0xff;
 
    if ((err = snd_pcm_open(&handle, device, SND_PCM_STREAM_PLAYBACK, 0)) < 0) {
        printf("Playback open error: %s\n", snd_strerror(err));
        exit(EXIT_FAILURE);
    }
    if ((err = snd_pcm_set_params(handle,
                      SND_PCM_FORMAT_U8,
                      SND_PCM_ACCESS_RW_INTERLEAVED,
                      1,
                      48000,
                      1,
                      500000)) < 0) {   /* 0.5sec */
        printf("Playback open error: %s\n", snd_strerror(err));
        exit(EXIT_FAILURE);
    }
 
        for (i = 0; i < 16; i++) {
        frames = snd_pcm_writei(handle, buffer, sizeof(buffer));
        if (frames < 0)
            frames = snd_pcm_recover(handle, frames, 0);
        if (frames < 0) {
            printf("snd_pcm_writei failed: %s\n", snd_strerror(frames));
            break;
        }
        if (frames > 0 && frames < (long)sizeof(buffer))
            printf("Short write (expected %li, wrote %li)\n", (long)sizeof(buffer), frames);
    }
 
    /* pass the remaining samples, otherwise they're dropped in close */
    err = snd_pcm_drain(handle);
    if (err < 0)
        printf("snd_pcm_drain failed: %s\n", snd_strerror(err));
    snd_pcm_close(handle);
    return 0;
}

编译此文件: gcc -o pcm_min pcm_min.c -lasound -lm

执行文件:./pcm_min

        这个文件产生一个随机噪声,写到声卡buffer里面播放声音。

录制声音参考 latency.c 

/*
 *  Latency test program
 *
 *     Author: Jaroslav Kysela 
 *
 *     Author of bandpass filter sweep effect:
 *         Maarten de Boer 
 *
 *  This small demo program can be used for measuring latency between
 *  capture and playback. This latency is measured from driver (diff when
 *  playback and capture was started). Scheduler is set to SCHED_RR.
 *
 *
 *   This program is free software; you can redistribute it and/or modify
 *   it under the terms of the GNU General Public License as published by
 *   the Free Software Foundation; either version 2 of the License, or
 *   (at your option) any later version.
 *
 *   This program is distributed in the hope that it will be useful,
 *   but WITHOUT ANY WARRANTY; without even the implied warranty of
 *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *   GNU General Public License for more details.
 *
 *   You should have received a copy of the GNU General Public License
 *   along with this program; if not, write to the Free Software
 *   Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA
 *
 */
 
#include 
#include 
#include 
#include 
#include 
#include 
#include "../include/asoundlib.h"
#include 
#include 
 
char *pdevice = "hw:0,0";
char *cdevice = "hw:0,0";
snd_pcm_format_t format = SND_PCM_FORMAT_S16_LE;
int rate = 22050;
int channels = 2;
int buffer_size = 0;        /* auto */
int period_size = 0;        /* auto */
int latency_min = 32;       /* in frames / 2 */
int latency_max = 2048;     /* in frames / 2 */
int loop_sec = 30;      /* seconds */
int block = 0;          /* block mode */
int use_poll = 0;
int resample = 1;
unsigned long loop_limit;
 
snd_output_t *output = NULL;
 
int setparams_stream(snd_pcm_t *handle,
             snd_pcm_hw_params_t *params,
             const char *id)
{
    int err;
    unsigned int rrate;
 
    err = snd_pcm_hw_params_any(handle, params);
    if (err < 0) {
        printf("Broken configuration for %s PCM: no configurations available: %s\n", snd_strerror(err), id);
        return err;
    }
    err = snd_pcm_hw_params_set_rate_resample(handle, params, resample);
    if (err < 0) {
        printf("Resample setup failed for %s (val %i): %s\n", id, resample, snd_strerror(err));
        return err;
    }
    err = snd_pcm_hw_params_set_access(handle, params, SND_PCM_ACCESS_RW_INTERLEAVED);
    if (err < 0) {
        printf("Access type not available for %s: %s\n", id, snd_strerror(err));
        return err;
    }
    err = snd_pcm_hw_params_set_format(handle, params, format);
    if (err < 0) {
        printf("Sample format not available for %s: %s\n", id, snd_strerror(err));
        return err;
    }
    err = snd_pcm_hw_params_set_channels(handle, params, channels);
    if (err < 0) {
        printf("Channels count (%i) not available for %s: %s\n", channels, id, snd_strerror(err));
        return err;
    }
    rrate = rate;
    err = snd_pcm_hw_params_set_rate_near(handle, params, &rrate, 0);
    if (err < 0) {
        printf("Rate %iHz not available for %s: %s\n", rate, id, snd_strerror(err));
        return err;
    }
    if ((int)rrate != rate) {
        printf("Rate doesn't match (requested %iHz, get %iHz)\n", rate, err);
        return -EINVAL;
    }
    return 0;
}
 
int setparams_bufsize(snd_pcm_t *handle,
              snd_pcm_hw_params_t *params,
              snd_pcm_hw_params_t *tparams,
              snd_pcm_uframes_t bufsize,
              const char *id)
{
    int err;
    snd_pcm_uframes_t periodsize;
 
    snd_pcm_hw_params_copy(params, tparams);
    periodsize = bufsize * 2;
    err = snd_pcm_hw_params_set_buffer_size_near(handle, params, &periodsize);
    if (err < 0) {
        printf("Unable to set buffer size %li for %s: %s\n", bufsize * 2, id, snd_strerror(err));
        return err;
    }
    if (period_size > 0)
        periodsize = period_size;
    else
        periodsize /= 2;
    err = snd_pcm_hw_params_set_period_size_near(handle, params, &periodsize, 0);
    if (err < 0) {
        printf("Unable to set period size %li for %s: %s\n", periodsize, id, snd_strerror(err));
        return err;
    }
    return 0;
}
 
int setparams_set(snd_pcm_t *handle,
          snd_pcm_hw_params_t *params,
          snd_pcm_sw_params_t *swparams,
          const char *id)
{
    int err;
    snd_pcm_uframes_t val;
 
    err = snd_pcm_hw_params(handle, params);
    if (err < 0) {
        printf("Unable to set hw params for %s: %s\n", id, snd_strerror(err));
        return err;
    }
    err = snd_pcm_sw_params_current(handle, swparams);
    if (err < 0) {
        printf("Unable to determine current swparams for %s: %s\n", id, snd_strerror(err));
        return err;
    }
    err = snd_pcm_sw_params_set_start_threshold(handle, swparams, 0x7fffffff);
    if (err < 0) {
        printf("Unable to set start threshold mode for %s: %s\n", id, snd_strerror(err));
        return err;
    }
    if (!block)
        val = 4;
    else
        snd_pcm_hw_params_get_period_size(params, &val, NULL);
    err = snd_pcm_sw_params_set_avail_min(handle, swparams, val);
    if (err < 0) {
        printf("Unable to set avail min for %s: %s\n", id, snd_strerror(err));
        return err;
    }
    err = snd_pcm_sw_params(handle, swparams);
    if (err < 0) {
        printf("Unable to set sw params for %s: %s\n", id, snd_strerror(err));
        return err;
    }
    return 0;
}
//设定软件硬件参数 
int setparams(snd_pcm_t *phandle, snd_pcm_t *chandle, int *bufsize)
{
    int err, last_bufsize = *bufsize;
    snd_pcm_hw_params_t *pt_params, *ct_params; /* templates with rate, format and channels */
    snd_pcm_hw_params_t *p_params, *c_params;
    snd_pcm_sw_params_t *p_swparams, *c_swparams;
    snd_pcm_uframes_t p_size, c_size, p_psize, c_psize;
    unsigned int p_time, c_time;
    unsigned int val;
 
    snd_pcm_hw_params_alloca(&p_params);
    snd_pcm_hw_params_alloca(&c_params);
    snd_pcm_hw_params_alloca(&pt_params);
    snd_pcm_hw_params_alloca(&ct_params);
    snd_pcm_sw_params_alloca(&p_swparams);
    snd_pcm_sw_params_alloca(&c_swparams);
    if ((err = setparams_stream(phandle, pt_params, "playback")) < 0) {
        printf("Unable to set parameters for playback stream: %s\n", snd_strerror(err));
        exit(0);
    }
    if ((err = setparams_stream(chandle, ct_params, "capture")) < 0) {
        printf("Unable to set parameters for playback stream: %s\n", snd_strerror(err));
        exit(0);
    }
 
    if (buffer_size > 0) {
        *bufsize = buffer_size;
        goto __set_it;
    }
 
      __again:
        if (buffer_size > 0)
            return -1;
        if (last_bufsize == *bufsize)
        *bufsize += 4;
    last_bufsize = *bufsize;
    if (*bufsize > latency_max)
        return -1;
      __set_it:
    if ((err = setparams_bufsize(phandle, p_params, pt_params, *bufsize, "playback")) < 0) {
        printf("Unable to set sw parameters for playback stream: %s\n", snd_strerror(err));
        exit(0);
    }
    if ((err = setparams_bufsize(chandle, c_params, ct_params, *bufsize, "capture")) < 0) {
        printf("Unable to set sw parameters for playback stream: %s\n", snd_strerror(err));
        exit(0);
    }
 
    snd_pcm_hw_params_get_period_size(p_params, &p_psize, NULL);
    if (p_psize > (unsigned int)*bufsize)
        *bufsize = p_psize;
    snd_pcm_hw_params_get_period_size(c_params, &c_psize, NULL);
    if (c_psize > (unsigned int)*bufsize)
        *bufsize = c_psize;
    snd_pcm_hw_params_get_period_time(p_params, &p_time, NULL);
    snd_pcm_hw_params_get_period_time(c_params, &c_time, NULL);
    if (p_time != c_time)
        goto __again;
 
    snd_pcm_hw_params_get_buffer_size(p_params, &p_size);
    if (p_psize * 2 < p_size) {
                snd_pcm_hw_params_get_periods_min(p_params, &val, NULL);
                if (val > 2) {
            printf("playback device does not support 2 periods per buffer\n");
            exit(0);
        }
        goto __again;
    }
    snd_pcm_hw_params_get_buffer_size(c_params, &c_size);
    if (c_psize * 2 < c_size) {
                snd_pcm_hw_params_get_periods_min(c_params, &val, NULL);
        if (val > 2 ) {
            printf("capture device does not support 2 periods per buffer\n");
            exit(0);
        }
        goto __again;
    }
    if ((err = setparams_set(phandle, p_params, p_swparams, "playback")) < 0) {
        printf("Unable to set sw parameters for playback stream: %s\n", snd_strerror(err));
        exit(0);
    }
    if ((err = setparams_set(chandle, c_params, c_swparams, "capture")) < 0) {
        printf("Unable to set sw parameters for playback stream: %s\n", snd_strerror(err));
        exit(0);
    }
 
    if ((err = snd_pcm_prepare(phandle)) < 0) {
        printf("Prepare error: %s\n", snd_strerror(err));
        exit(0);
    }
 
    snd_pcm_dump(phandle, output);
    snd_pcm_dump(chandle, output);
    fflush(stdout);
    return 0;
}
 
void showstat(snd_pcm_t *handle, size_t frames)
{
    int err;
    snd_pcm_status_t *status;
 
    snd_pcm_status_alloca(&status);
    if ((err = snd_pcm_status(handle, status)) < 0) {
        printf("Stream status error: %s\n", snd_strerror(err));
        exit(0);
    }
    printf("*** frames = %li ***\n", (long)frames);
    snd_pcm_status_dump(status, output);
}
 
void showlatency(size_t latency)
{
    double d;
    latency *= 2;
    d = (double)latency / (double)rate;
    printf("Trying latency %li frames, %.3fus, %.6fms (%.4fHz)\n", (long)latency, d * 1000000, d * 1000, (double)1 / d);
}
 
void showinmax(size_t in_max)
{
    double d;
 
    printf("Maximum read: %li frames\n", (long)in_max);
    d = (double)in_max / (double)rate;
    printf("Maximum read latency: %.3fus, %.6fms (%.4fHz)\n", d * 1000000, d * 1000, (double)1 / d);
}
 
void gettimestamp(snd_pcm_t *handle, snd_timestamp_t *timestamp)
{
    int err;
    snd_pcm_status_t *status;
 
    snd_pcm_status_alloca(&status);
    if ((err = snd_pcm_status(handle, status)) < 0) {
        printf("Stream status error: %s\n", snd_strerror(err));
        exit(0);
    }
    snd_pcm_status_get_trigger_tstamp(status, timestamp);
}
 
void setscheduler(void)
{
    struct sched_param sched_param;
 
    if (sched_getparam(0, &sched_param) < 0) {
        printf("Scheduler getparam failed...\n");
        return;
    }
    sched_param.sched_priority = sched_get_priority_max(SCHED_RR);
    if (!sched_setscheduler(0, SCHED_RR, &sched_param)) {
        printf("Scheduler set to Round Robin with priority %i...\n", sched_param.sched_priority);
        fflush(stdout);
        return;
    }
    printf("!!!Scheduler set to Round Robin with priority %i FAILED!!!\n", sched_param.sched_priority);
}
 
long timediff(snd_timestamp_t t1, snd_timestamp_t t2)
{
    signed long l;
 
    t1.tv_sec -= t2.tv_sec;
    l = (signed long) t1.tv_usec - (signed long) t2.tv_usec;
    if (l < 0) {
        t1.tv_sec--;
        l = 1000000 + l;
        l %= 1000000;
    }
    return (t1.tv_sec * 1000000) + l;
}
 
long readbuf(snd_pcm_t *handle, char *buf, long len, size_t *frames, size_t *max)
{
    long r;
 
    if (!block) {
        do {
            r = snd_pcm_readi(handle, buf, len);
        } while (r == -EAGAIN);
        if (r > 0) {
            *frames += r;
            if ((long)*max < r)
                *max = r;
        }
        // printf("read = %li\n", r);
    } else {
        int frame_bytes = (snd_pcm_format_width(format) / 8) * channels;
        do {
            r = snd_pcm_readi(handle, buf, len);
            if (r > 0) {
                buf += r * frame_bytes;
                len -= r;
                *frames += r;
                if ((long)*max < r)
                    *max = r;
            }
            // printf("r = %li, len = %li\n", r, len);
        } while (r >= 1 && len > 0);
    }
    // showstat(handle, 0);
    return r;
}
 
long writebuf(snd_pcm_t *handle, char *buf, long len, size_t *frames)
{
    long r;
    int frame_bytes = (snd_pcm_format_width(format) / 8) * channels;
 
    while (len > 0) {
        r = snd_pcm_writei(handle, buf, len);
        if (r == -EAGAIN)
            continue;
        // printf("write = %li\n", r);
        if (r < 0)
            return r;
        // showstat(handle, 0);
        buf += r * frame_bytes;
        len -= r;
        *frames += r;
    }
    return 0;
}
            
#define FILTERSWEEP_LFO_CENTER 2000.
#define FILTERSWEEP_LFO_DEPTH 1800.
#define FILTERSWEEP_LFO_FREQ 0.2
#define FILTER_BANDWIDTH 50
 
/* filter the sweep variables */
float lfo,dlfo,fs,fc,BW,C,D,a0,a1,a2,b1,b2,*x[3],*y[3];
 
void applyeffect(char* buffer,int r)
{
    short* samples = (short*) buffer;
    int i;
    for (i=0;i2.*M_PI) lfo -= 2.*M_PI;
        C = 1./tan(M_PI*BW/fs);
        D = 2.*cos(2*M_PI*fc/fs);
        a0 = 1./(1.+C);
        a1 = 0;
        a2 = -a0;
        b1 = -C*D*a0;
        b2 = (C-1)*a0;
 
        for (chn=0;chn= 4 ? err : 4;
            if (latency_max < latency_min)
                latency_max = latency_min;
            break;
        case 'M':
            err = atoi(optarg) / 2;
            latency_max = latency_min > err ? latency_min : err;
            break;
        case 'f':
            format = snd_pcm_format_value(optarg);
            if (format == SND_PCM_FORMAT_UNKNOWN) {
                printf("Unknown format, setting to default S16_LE\n");
                format = SND_PCM_FORMAT_S16_LE;
            }
            break;
        case 'c':
            err = atoi(optarg);
            channels = err >= 1 && err < 1024 ? err : 1;
            break;
        case 'r':
            err = atoi(optarg);
            rate = err >= 4000 && err < 200000 ? err : 44100;
            break;
        case 'B':
            err = atoi(optarg);
            buffer_size = err >= 32 && err < 200000 ? err : 0;
            break;
        case 'E':
            err = atoi(optarg);
            period_size = err >= 32 && err < 200000 ? err : 0;
            break;
        case 's':
            err = atoi(optarg);
            loop_sec = err >= 1 && err <= 100000 ? err : 30;
            break;
        case 'b':
            block = 1;
            break;
        case 'p':
            use_poll = 1;
            break;
        case 'e':
            effect = 1;
            break;
        case 'n':
            resample = 0;
            break;
        }
    }
 
    if (morehelp) {
        help();
        return 0;
    }
	
	//把输出重定向到stdout
    err = snd_output_stdio_attach(&output, stdout, 0);
    if (err < 0) {
        printf("Output failed: %s\n", snd_strerror(err));
        return 0;
    }
 
    loop_limit = loop_sec * rate;
    latency = latency_min - 4;
    buffer = malloc((latency_max * snd_pcm_format_width(format) / 8) * 2);
	//设定进程调度相关
    setscheduler();
 
    printf("Playback device is %s\n", pdevice);
    printf("Capture device is %s\n", cdevice);
    printf("Parameters are %iHz, %s, %i channels, %s mode\n", rate, snd_pcm_format_name(format), channels, block ? "blocking" : "non-blocking");
    printf("Poll mode: %s\n", use_poll ? "yes" : "no");
    printf("Loop limit is %lu frames, minimum latency = %i, maximum latency = %i\n", loop_limit, latency_min * 2, latency_max * 2);
	//打开播放设备
    if ((err = snd_pcm_open(&phandle, pdevice, SND_PCM_STREAM_PLAYBACK, block ? 0 : SND_PCM_NONBLOCK)) < 0) {
        printf("Playback open error: %s\n", snd_strerror(err));
        return 0;
    }
	//打开录音设备
    if ((err = snd_pcm_open(&chandle, cdevice, SND_PCM_STREAM_CAPTURE, block ? 0 : SND_PCM_NONBLOCK)) < 0) {
        printf("Record open error: %s\n", snd_strerror(err));
        return 0;
    }
 
    /* initialize the filter sweep variables */
    if (effect) {
        fs = (float) rate;
        BW = FILTER_BANDWIDTH;
 
        lfo = 0;
        dlfo = 2.*M_PI*FILTERSWEEP_LFO_FREQ/fs;
 
        x[0] = (float*) malloc(channels*sizeof(float));     
        x[1] = (float*) malloc(channels*sizeof(float));     
        x[2] = (float*) malloc(channels*sizeof(float));     
        y[0] = (float*) malloc(channels*sizeof(float));     
        y[1] = (float*) malloc(channels*sizeof(float));     
        y[2] = (float*) malloc(channels*sizeof(float));     
    }
              
    while (1) {
        frames_in = frames_out = 0;
        if (setparams(phandle, chandle, &latency) < 0)
            break;
        showlatency(latency);
        if ((err = snd_pcm_link(chandle, phandle)) < 0) {
            printf("Streams link error: %s\n", snd_strerror(err));
            exit(0);
        }
        if (snd_pcm_format_set_silence(format, buffer, latency*channels) < 0) {
            fprintf(stderr, "silence error\n");
            break;
        }
        if (writebuf(phandle, buffer, latency, &frames_out) < 0) {
            fprintf(stderr, "write error\n");
            break;
        }
        if (writebuf(phandle, buffer, latency, &frames_out) < 0) {
            fprintf(stderr, "write error\n");
            break;
        }
 
        if ((err = snd_pcm_start(chandle)) < 0) {
            printf("Go error: %s\n", snd_strerror(err));
            exit(0);
        }
        gettimestamp(phandle, &p_tstamp);
        gettimestamp(chandle, &c_tstamp);
#if 0
        printf("Playback:\n");
        showstat(phandle, frames_out);
        printf("Capture:\n");
        showstat(chandle, frames_in);
#endif
 
        ok = 1;
        in_max = 0;
        while (ok && frames_in < loop_limit) {
            if (use_poll) {
                /* use poll to wait for next event */
                snd_pcm_wait(chandle, 1000);
            }
            if ((r = readbuf(chandle, buffer, latency, &frames_in, &in_max)) < 0)
                ok = 0;
            else {
                if (effect)
                    applyeffect(buffer,r);
                if (writebuf(phandle, buffer, r, &frames_out) < 0)
                    ok = 0;
            }
        }
        if (ok)
            printf("Success\n");
        else
            printf("Failure\n");
        printf("Playback:\n");
        showstat(phandle, frames_out);
        printf("Capture:\n");
        showstat(chandle, frames_in);
        showinmax(in_max);
        if (p_tstamp.tv_sec == c_tstamp.tv_sec &&
            p_tstamp.tv_usec == c_tstamp.tv_usec)
            printf("Hardware sync\n");
        snd_pcm_drop(chandle);
        snd_pcm_nonblock(phandle, 0);
        snd_pcm_drain(phandle);
        snd_pcm_nonblock(phandle, !block ? 1 : 0);
        if (ok) {
#if 1
            printf("Playback time = %li.%i, Record time = %li.%i, diff = %li\n",
                   p_tstamp.tv_sec,
                   (int)p_tstamp.tv_usec,
                   c_tstamp.tv_sec,
                   (int)c_tstamp.tv_usec,
                   timediff(p_tstamp, c_tstamp));
#endif
            break;
        }
        snd_pcm_unlink(chandle);
        snd_pcm_hw_free(phandle);
        snd_pcm_hw_free(chandle);
    }
    snd_pcm_close(phandle);
    snd_pcm_close(chandle);
    return 0;
}

录音设备这里写得比较复杂可以参考我上传的书籍资料里面的课件。

参考资料:

《Linux高级程序设计第三版(中文)》        作者:杨宗德

《Linux环境编程图文指南》        作者:林世霖

ALSA官网:ALSA project - the C library reference: Index, Preamble and License

百问网:深圳百问网科技有限公司

alsa-lib以及pdf书籍资料链接:CSDN

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