C中ALSA的采样频率
我有一个使用ALSA库记录5秒音频值的程序,下面是代码:C中ALSA的采样频率,c,alsa,C,Alsa,我有一个使用ALSA库记录5秒音频值的程序,下面是代码: #define ALSA_PCM_NEW_HW_PARAMS_API #include <alsa/asoundlib.h> #include <stdio.h> int main() { long loops; int rc; int size; snd_pcm_t *handle; snd_pcm_hw_params_t *params; unsigned int val; int
#define ALSA_PCM_NEW_HW_PARAMS_API
#include <alsa/asoundlib.h>
#include <stdio.h>
int main() {
long loops;
int rc;
int size;
snd_pcm_t *handle;
snd_pcm_hw_params_t *params;
unsigned int val;
int dir,z=0;
snd_pcm_uframes_t frames;
signed short *buffer;
FILE* inp = NULL;
FILE* inp2 =NULL;
inp = fopen("values","wb+");
inp2 = fopen("Values2","w+");
int fd = open("v",O_WRONLY);
/* Open PCM device for recording (capture). */
rc = snd_pcm_open(&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(¶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);
/* Sample frequency */
val = 96000;
//val2 = val;
snd_pcm_hw_params_set_rate(handle, params,
val, &dir);
printf(" %d \n", val);
/* Set period size to 32 frames. */
frames = 32;
snd_pcm_hw_params_set_period_size_near(handle,
params, &frames, &dir);
/* 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));
exit(1);
}
/* Use a buffer large enough to hold one period */
snd_pcm_hw_params_get_period_size(params,
&frames, &dir);
size = frames * 1; /* 2 bytes/sample, 1 channels */
buffer = (signed short*) malloc(size);
/* We want to loop for 5 seconds */
snd_pcm_hw_params_get_period_time(params,
&val, &dir);
loops = 5000000 / val;
while (loops > 0) {
loops--;
rc = snd_pcm_readi(handle, buffer, frames);
fwrite(buffer,sizeof(signed short),size,inp);
for(z =0; z<size;z++)
fprintf(inp2,"%lf\n",buffer[z]/1.0);
}
snd_pcm_drain(handle);
snd_pcm_close(handle);
printf(" buffer");
free(buffer);
fclose(inp);
fclose(inp2);
close(fd);
return 0;
}
我已经检查了参数类型是否正确,但更有趣的是,在运行程序后,我得到了另一个错误:
*** Error in `./out': malloc(): memory corruption (fast): 0x0000000002462d90 ***
中止(堆芯转储)
当我使用以下选项时,此选项不会显示:
size = frames * 1; to
size = frames * 2;
a结果是错误的,我尝试使用较低的采样频率,但没有帮助。
使用时:snd_pcm_hw_params_set_rate_near
sample freuqency更改为192000,结果非常正确,我会真正使用第一个函数,以便了解我使用的采样频率
你知道我该怎么做吗?或者为什么我会得到那些战斗 关于警告,编译器是正确的,您正在传递类型为
int*
的dir
的地址关于警告,编译器是正确的,您正在传递dir
的地址,其类型为int*
。根据文档,您链接到的第四个参数应该是int
,而不是int*
。谢谢,这解决了第一个警告@引擎:我认为您应该使用buffer=(signed short*)malloc(size*sizeof(signed short))来分配缓冲区代码>@Engine:您现在如何调用snd_pcm_hw_params_set_rate()?是否为第四个参数传递了正确的值。查看文档,我认为有效值是-1、0和1。我输入了0,它可以很好地用于记录。我现在遇到的唯一问题是,当我输入fs=96000时,我得到480448个值,持续5秒,这是不正确的!事实上,对于不同的fs值,我没有得到我应该得到的样本数!我可能错了,但我认为读取循环根本不准确。也许有更准确的方法?我想你应该检查一下。进一步阅读文档,它指出snd_pcm_hw_params_get_period_time
中的值是近似的最大周期持续时间,单位为us
。
size = frames * 1; to
size = frames * 2;