alsa学习--3.alsa的demo

Introduction to Sound Programming with ALSA
http://www.linuxjournal.com/article/6735

---

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

1. #include "utils.h"
   
2. #include <alsa/asoundlib.h>
   
3. #include <stdlib.h>
   
4. 
   
5. int main ( int argc, char *argv[] )
   
6. {
   
7.     int i;
   
8.     printf("<----- 1="" -----="">ALSA library version=%s\n", SND_LIB_VERSION_STR);
   
9. 
   
10.     printf("\n<----- 2="" -----="">PCM stream types:\n");
    
11.     for(i=0; i<=SND_PCM_STREAM_LAST; i++)
    
12.         printf("%s\n", snd_pcm_stream_name((snd_pcm_stream_t)i));
    
13. 
    
14.     printf("\n<----- 3="" -----="">PCM access type:\n");
    
15.     for(i=0; i<=SND_PCM_ACCESS_LAST; i++)
    
16.         printf("%s\n", snd_pcm_access_name((snd_pcm_access_t)i));
    
17. 
    
18.     printf("\n<----- 4="" -----="">PCM formats:\n");
    
19.     for(i=0; i<=SND_PCM_FORMAT_LAST; i++)
    
20.     { 
    
21.         if(NULL != snd_pcm_format_name((snd_pcm_format_t)i))
    
22.         {
    
23.             printf("%s:%s\n", snd_pcm_format_name((snd_pcm_format_t)i), 
    
24.                     snd_pcm_format_description((snd_pcm_format_t)i));
    
25.         }
    
26.     }
    
27. 
    
28.     printf("\n<----- 5="" -----="">PCM subformats:\n");
    
29.     for(i=0; i<=SND_PCM_SUBFORMAT_LAST; i++)
    
30.     { 
    
31.         printf("%s:%s\n", snd_pcm_subformat_name((snd_pcm_subformat_t)i), 
    
32.                 snd_pcm_subformat_description((snd_pcm_subformat_t)i));
    
33.     }
    
34. 
    
35.     printf("\n<----- 6="" -----="">PCM state:\n");
    
36.     for(i=0; i<=SND_PCM_STATE_LAST; i++)
    
37.     { 
    
38.         printf("%s\n", snd_pcm_state_name((snd_pcm_state_t)i)); 
    
39.     }
    
40.     return EXIT_SUCCESS;
    
41. }

Makefile

1. EXE=start
   
2. CC=gcc
   
3. ALSA_PATH=/work/ffmpeg/test/alsa/alsa-lib-1.0.23/_install/
   
4. RESOURCE=/work/ffmpeg/test/resource/
   
5. 
   
6. CFLAGS=-g -O0
   
7. CFLAGS += -I$(ALSA_PATH)/include
   
8. LDFLAGS += -L$(ALSA_PATH)/lib/ -lrt -lasound -lm -ldl -lpthread
   
9. 
   
10. SRC=$(wildcard *.c)
    
11. OBJ=$(patsubst %.c,%.o,$(SRC))
    
12. DEP=$(patsubst %.c,.%.d,$(SRC))
    
13. $(EXE):$(OBJ)
    
14.     $(CC) $(CFLAGS) $^ -o $@ $(LDFLAGS)
    
15. 
    
16. $(DEP):.%.d:%.c
    
17.     @set -e; rm -f $@; \
    
18.     $(CC) -MM $< > $@.$$$$; \
    
19.     sed 's,/($*/)/.o[ :]*,/1.o $@ : ,g' < $@.$$$$ > $@; \
    
20.     rm -f $@.$$$$
    
21. 
    
22. -include $(DEP)
    
23. clean:
    
24.     @rm $(EXE) $(OBJ) $(DEP) -f
    
25. run:
    
26.     export LD_LIBRARY_PATH=$(FFMPEG)/lib/ \
    
27.     && ./$(EXE) $(RESOURCE)/test.wav
    
28.     #&& ./$(EXE) ../resource/test.wmv

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

---

二. param

1. #include "utils.h"
   
2. #include <alsa/asoundlib.h>
   
3. #include <stdlib.h>
   
4. 
   
5. int main ( int argc, char *argv[] )
   
6. {
   
7.     int i;
   
8.     int ret;
   
9.     int dir;
   
10.     unsigned int val, val2;
    
11.     snd_pcm_t* handle;
    
12.     snd_pcm_hw_params_t* params;
    
13.     //1. open
    
14.     if( (ret = snd_pcm_open(&handle, "default", SND_PCM_STREAM_PLAYBACK, 0)) < 0)
    
15.     {
    
16.         dbmsg("open pcm device error:%s", snd_strerror(ret));
    
17.         return -1;
    
18.     }
    
19.     //2. alloc and init param
    
20.     snd_pcm_hw_params_alloca(&params);
    
21.     snd_pcm_hw_params_any(handle, params);
    
22.     snd_pcm_hw_params_set_access(handle, params, SND_PCM_ACCESS_RW_INTERLEAVED);
    
23.     snd_pcm_hw_params_set_format(handle, params, SND_PCM_FORMAT_S16_LE);
    
24.     snd_pcm_hw_params_set_channels(handle, params, 2);
    
25.     val = 44100;
    
26.     snd_pcm_hw_params_set_rate_near(handle,params, &val, &dir);
    
27.     
    
28.     //3. set param to driver
    
29.     if((ret=snd_pcm_hw_params(handle, params)) < 0)
    
30.     {
    
31.         dbmsg("set hw params error:%s", snd_strerror(ret));
    
32.         return -1;
    
33.     }
    
34.     
    
35.     printf("PCM handle name=%s\n", snd_pcm_name(handle));
    
36.     printf("PCM state=%s\n", snd_pcm_state_name(snd_pcm_state(handle)));
    
37.     
    
38.     snd_pcm_hw_params_get_access(params, (snd_pcm_access_t*)&val);
    
39.     printf("access type=%s\n",snd_pcm_access_name((snd_pcm_access_t)val));
    
40. 
    
41.     snd_pcm_hw_params_get_format(params, &val);
    
42.     printf("format=%s (%s)\n",snd_pcm_format_name((snd_pcm_format_t)val),
    
43.             snd_pcm_format_description((snd_pcm_format_t)val));
    
44.     
    
45.     snd_pcm_close(handle);
    
46.     return EXIT_SUCCESS;
    
47. }

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

---

三.play sound
3.1 

1. #include "utils.h"
   
2. #define ALSA_PCM_NEW_HW_PARAMS_API
   
3. #include <alsa/asoundlib.h>
   
4. #include <stdlib.h>
   
5. 
   
6. int main ( int argc, char *argv[] )
   
7. {
   
8.     int i;
   
9.     int ret, dir, size;
   
10.     long loops;
    
11.     unsigned int val, val2;
    
12.     char* buffer;
    
13.     snd_pcm_t* handle;
    
14.     snd_pcm_hw_params_t* params;
    
15.     snd_pcm_uframes_t frames;
    
16.     //1. open
    
17.     if( (ret = snd_pcm_open(&handle, "default", SND_PCM_STREAM_PLAYBACK, 0)) < 0)
    
18.     {
    
19.         dbmsg("open pcm device error:%s", snd_strerror(ret));
    
20.         return -1;
    
21.     }
    
22.     //2. alloc and init param
    
23.     snd_pcm_hw_params_alloca(&params);
    
24.     snd_pcm_hw_params_any(handle, params);
    
25.     snd_pcm_hw_params_set_access(handle, params, SND_PCM_ACCESS_RW_INTERLEAVED);
    
26.     snd_pcm_hw_params_set_format(handle, params, SND_PCM_FORMAT_S16_LE);
    
27.     snd_pcm_hw_params_set_channels(handle, params, 2);
    
28.     val = 44100;
    
29.     snd_pcm_hw_params_set_rate_near(handle,params, &val, &dir);
    
30.     frames = 32;
    
31.     snd_pcm_hw_params_set_period_size_near(handle, params, &frames, &dir);
    
32.     //3. set param to driver
    
33.     if((ret=snd_pcm_hw_params(handle, params)) < 0)
    
34.     {
    
35.         dbmsg("set hw params error:%s", snd_strerror(ret));
    
36.         return -1;
    
37.     }
    
38. 
    
39.     snd_pcm_hw_params_get_period_size(params, &frames, &dir);
    
40.     size = frames*4; //2byte/smaple, 2 channels
    
41.     buffer = (char*)malloc(size);
    
42. 
    
43.     snd_pcm_hw_params_get_period_time(params, &val, &dir);
    
44.     loops = 5000000/val;
    
45.     dbmsg("next in loop,loops=%ld,val=%d",loops, val);
    
46.     while(loops>0)
    
47.     {
    
48.         loops --;
    
49.         ret = read(0, buffer, size);
    
50.         dbmsg("ret =%d", ret);
    
51.         if(ret==0)
    
52.         {
    
53.             dbmsg("end of file");
    
54.             return 0;
    
55.         }else if (ret!=size)
    
56.         {
    
57.             dbmsg("short read");
    
58.         }
    
59.         
    
60.         ret = snd_pcm_writei(handle, buffer, frames);
    
61.         if(ret == -EPIPE)
    
62.         {
    
63.             dbmsg("-EPIPE");
    
64.             snd_pcm_prepare(handle);
    
65.         }
    
66.     }
    
67.     
    
68.     snd_pcm_drain(handle);
    
69.     snd_pcm_close(handle);
    
70.     free(buffer);
    
71.     return EXIT_SUCCESS;
    
72. }

运行,会听到一些杂音

1. 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.)