alsa学习--3.alsa的demo

Introduction to Sound Programming with ALSA

---

1. 打印alsa中的类型及格式
Listing 1. Display Some PCM Types and Formats

#include "utils.h"
#include <alsa/asoundlib.h>
#include <stdlib.h>

int main ( int argc, char *argv[] )
{
    int i;
    printf("<----- 1="" -----="">ALSA library version=%s\n", SND_LIB_VERSION_STR);

    printf("\n<----- 2="" -----="">PCM stream types:\n");
    for(i=0; i<=SND_PCM_STREAM_LAST; i++)
        printf("%s\n", snd_pcm_stream_name((snd_pcm_stream_t)i));

    printf("\n<----- 3="" -----="">PCM access type:\n");
    for(i=0; i<=SND_PCM_ACCESS_LAST; i++)
        printf("%s\n", snd_pcm_access_name((snd_pcm_access_t)i));

    printf("\n<----- 4="" -----="">PCM formats:\n");
    for(i=0; i<=SND_PCM_FORMAT_LAST; i++)
    {
        if(NULL != snd_pcm_format_name((snd_pcm_format_t)i))
        {
            printf("%s:%s\n", snd_pcm_format_name((snd_pcm_format_t)i),
                    snd_pcm_format_description((snd_pcm_format_t)i));
        }
    }

    printf("\n<----- 5="" -----="">PCM subformats:\n");
    for(i=0; i<=SND_PCM_SUBFORMAT_LAST; i++)
    {
        printf("%s:%s\n", snd_pcm_subformat_name((snd_pcm_subformat_t)i),
                snd_pcm_subformat_description((snd_pcm_subformat_t)i));
    }

    printf("\n<----- 6="" -----="">PCM state:\n");
    for(i=0; i<=SND_PCM_STATE_LAST; i++)
    {
        printf("%s\n", snd_pcm_state_name((snd_pcm_state_t)i));
    }
    return EXIT_SUCCESS;
}

Makefile

EXE=start
CC=gcc
ALSA_PATH=/work/ffmpeg/test/alsa/alsa-lib-1.0.23/_install/
RESOURCE=/work/ffmpeg/test/resource/

CFLAGS=-g -O0
CFLAGS += -I$(ALSA_PATH)/include
LDFLAGS += -L$(ALSA_PATH)/lib/ -lrt -lasound -lm -ldl -lpthread

SRC=$(wildcard *.c)
OBJ=$(patsubst %.c,%.o,$(SRC))
DEP=$(patsubst %.c,.%.d,$(SRC))
$(EXE):$(OBJ)
    $(CC) $(CFLAGS) $^ -o $@ $(LDFLAGS)

$(DEP):.%.d:%.c
    @set -e; rm -f $@; \
    $(CC) -MM  $< > $@.$$$$; \
    sed 's,/($*/)/.o[ :]*,/1.o $@ : ,g' < $@.$$$$ > $@; \
    rm -f $@.$$$$

-include $(DEP)
clean:
    @rm $(EXE) $(OBJ) $(DEP) -f
run:
    export LD_LIBRARY_PATH=$(FFMPEG)/lib/ \
    && ./$(EXE) $(RESOURCE)/test.wav
    #&& ./$(EXE) ../resource/test.wmv

1.2 代码打包
1start.rar(下载后改名为1start.tar.gz)

---

二. param

#include "utils.h"
#include <alsa/asoundlib.h>
#include <stdlib.h>

int main ( int argc, char *argv[] )
{
    int i;
    int ret;
    int dir;
    unsigned int val, val2;
    snd_pcm_t* handle;
    snd_pcm_hw_params_t* params;
    //1. open
    if( (ret = snd_pcm_open(&handle, "default", SND_PCM_STREAM_PLAYBACK, 0)) < 0)
    {
        dbmsg("open pcm device error:%s", snd_strerror(ret));
        return -1;
    }
    //2. alloc and init param
    snd_pcm_hw_params_alloca(&params);
    snd_pcm_hw_params_any(handle, params);
    snd_pcm_hw_params_set_access(handle, params, SND_PCM_ACCESS_RW_INTERLEAVED);
    snd_pcm_hw_params_set_format(handle, params, SND_PCM_FORMAT_S16_LE);
    snd_pcm_hw_params_set_channels(handle, params, 2);
    val = 44100;
    snd_pcm_hw_params_set_rate_near(handle,params, &val, &dir);

    //3. set param to driver
    if((ret=snd_pcm_hw_params(handle, params)) < 0)
    {
        dbmsg("set hw params error:%s", snd_strerror(ret));
        return -1;
    }

    printf("PCM handle name=%s\n", snd_pcm_name(handle));
    printf("PCM state=%s\n", snd_pcm_state_name(snd_pcm_state(handle)));

    snd_pcm_hw_params_get_access(params, (snd_pcm_access_t*)&val);
    printf("access type=%s\n",snd_pcm_access_name((snd_pcm_access_t)val));

    snd_pcm_hw_params_get_format(params, &val);
    printf("format=%s (%s)\n",snd_pcm_format_name((snd_pcm_format_t)val),
            snd_pcm_format_description((snd_pcm_format_t)val));

    snd_pcm_close(handle);
    return EXIT_SUCCESS;
}

2.2 代码打包
2param.rar(下载后改名为2param.tar.gz)

---

三.play sound
3.1

#include "utils.h"
#define     ALSA_PCM_NEW_HW_PARAMS_API
#include <alsa/asoundlib.h>
#include <stdlib.h>

int main ( int argc, char *argv[] )
{
    int i;
    int ret, dir, size;
    long loops;
    unsigned int val, val2;
    char* buffer;
    snd_pcm_t* handle;
    snd_pcm_hw_params_t* params;
    snd_pcm_uframes_t frames;
    //1. open
    if( (ret = snd_pcm_open(&handle, "default", SND_PCM_STREAM_PLAYBACK, 0)) < 0)
    {
        dbmsg("open pcm device error:%s", snd_strerror(ret));
        return -1;
    }
    //2. alloc and init param
    snd_pcm_hw_params_alloca(&params);
    snd_pcm_hw_params_any(handle, params);
    snd_pcm_hw_params_set_access(handle, params, SND_PCM_ACCESS_RW_INTERLEAVED);
    snd_pcm_hw_params_set_format(handle, params, SND_PCM_FORMAT_S16_LE);
    snd_pcm_hw_params_set_channels(handle, params, 2);
    val = 44100;
    snd_pcm_hw_params_set_rate_near(handle,params, &val, &dir);
    frames = 32;
    snd_pcm_hw_params_set_period_size_near(handle, params, &frames, &dir);
    //3. set param to driver
    if((ret=snd_pcm_hw_params(handle, params)) < 0)
    {
        dbmsg("set hw params error:%s", snd_strerror(ret));
        return -1;
    }

    snd_pcm_hw_params_get_period_size(params, &frames, &dir);
    size = frames*4; //2byte/smaple, 2 channels
    buffer = (char*)malloc(size);

    snd_pcm_hw_params_get_period_time(params, &val, &dir);
    loops = 5000000/val;
    dbmsg("next in loop,loops=%ld,val=%d",loops, val);
    while(loops>0)
    {
        loops --;
        ret = read(0, buffer, size);
        dbmsg("ret =%d", ret);
        if(ret==0)
        {
            dbmsg("end of file");
            return 0;
        }else if (ret!=size)
        {
            dbmsg("short read");
        }

        ret = snd_pcm_writei(handle, buffer, frames);
        if(ret == -EPIPE)
        {
            dbmsg("-EPIPE");
            snd_pcm_prepare(handle);
        }
    }

    snd_pcm_drain(handle);
    snd_pcm_close(handle);
    free(buffer);
    return EXIT_SUCCESS;
}

运行,会听到一些杂音

cong@msi:/work/ffmpeg/test/alsa/testalsa/3play$ ./play < /dev/urandom

3.1代码打包
3play.rar(下载后改名为3play.)