在 NanoPi NEO 上使用 ALSA 錄音時聲音不清晰或尖銳噪音
[英]Unclear sound or high pitched noise when recording with ALSA on NanoPi NEO
問題描述
我正在為可以在Linuxjournal中找到的 ALSA 示例而苦苦掙扎
我將代碼復制到 .c 文件中並將它們編譯為gcc -Wall Record_Listing4.c -lasound -o record到可執行文件中：Listing3 as play和 Listing4 as record
我正在使用帶有UGO 聲卡的Nanopi NEO
我確保將默認音頻設備指向提到的 USB 聲卡。
我可以使用這個考試錄制聲音甚至聽它，但有一個問題：如果我按原樣管道./record |./play我會得到超響亮和高音調的噪音作為背景。
我發現我的耳機需要 2 個香奈兒立體聲，而我的麥克風需要 1 個香奈兒單聲道。 所以我試圖將這個單聲道與自身交錯以創建立體聲。
這帶來了一些成功，因為我設法消除了高音調噪音，但現在我的聲音中出現了某種靜態噪音。
這是我第一次嘗試直接使用聲音創建應用程序，所以我試圖理解為什么我會聽到噪音。 arecord工作正常並且記錄沒有問題，所以它不是硬件。
修改后的代碼如下
回放_Listing3
/*
This example reads standard from input and writes
to the default PCM device for 5 seconds of data.
*/
/* Use the newer ALSA API */
#define ALSA_PCM_NEW_HW_PARAMS_API
#include <alsa/asoundlib.h>
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;
char *buffer;
/* Open PCM device for playback. */
rc = snd_pcm_open(&handle, "default",
SND_PCM_STREAM_PLAYBACK, 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, 2);
/* 44100 bits/second sampling rate (CD quality) */
val = 44100;
snd_pcm_hw_params_set_rate_near(handle, params,
&val, &dir);
/* 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 * 4; /* 2 bytes/sample, 2 channels */
buffer = (char *) malloc(size);
/* We want to loop for 5 seconds */
snd_pcm_hw_params_get_period_time(params,
&val, &dir);
/* 5 seconds in microseconds divided by
* period time */
loops = 5000000 / val;
while (loops > 0) {
loops--;
rc = read(0, buffer, size);
if (rc == 0) {
fprintf(stderr, "end of file on input\n");
break;
} else if (rc != size) {
fprintf(stderr,
"short read: read %d bytes\n", rc);
}
rc = snd_pcm_writei(handle, buffer, frames);
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));
} else if (rc != (int)frames) {
fprintf(stderr,
"short write, write %d frames\n", rc);
}
}
snd_pcm_drain(handle);
snd_pcm_close(handle);
free(buffer);
return 0;
}
記錄清單4
/*
This example reads from the default PCM device
and writes to standard output for 5 seconds of data.
*/
/* Use the newer ALSA API */
#define ALSA_PCM_NEW_HW_PARAMS_API
#include <alsa/asoundlib.h>
void interleave(const char * in_L, // mono input buffer (left channel)
const char * in_R, // mono input buffer (right channel)
char * out, // stereo output buffer
const size_t num_samples) // number of samples
{
for (size_t i = 0; i < num_samples; ++i)
{
out[i * 4] = in_L[i];
out[i * 4 + 1] = in_L[i+1];
out[i * 4 + 2] = 0;
out[i * 4 + 3] = 0;
}
}
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;
char *buffer;
char *stereo;
/* 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);
/* 44100 bits/second sampling rate (CD quality) */
val = 44100;
snd_pcm_hw_params_set_rate_near(handle, params, &val, &dir);
/* 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 * 2; /* 2 bytes/sample, 2 channels */
buffer = (char *) malloc(size);
stereo = (char *) malloc(size*2);
/* 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);
if (rc == -EPIPE) {
/* EPIPE means overrun */
fprintf(stderr, "overrun occurred\n");
snd_pcm_prepare(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);
}
interleave(buffer, buffer, stereo, frames);
rc = write(1, stereo, size*2);
if (rc != size*2)
fprintf(stderr,
"short write: wrote %d bytes\n", rc);
}
snd_pcm_drain(handle);
snd_pcm_close(handle);
free(buffer);
return 0;
}
1 個解決方案
解決方案1
0 2022-12-21 13:57:12
更新
我已經設法解決了這個問題。 潛在的原因是記錄格式和回報格式之間的不一致。 我需要從麥克風中正確地交錯單聲道以創建沒有噪音或靜態的適當立體聲。 我在下面為任何掙扎的人發布代碼。
記錄
/*
This example reads from the default PCM device
and writes to standard output for 5 seconds of data.
*/
/* Use the newer ALSA API */
#define ALSA_PCM_NEW_HW_PARAMS_API
#include <alsa/asoundlib.h>
void interleave(const uint16_t * in_L, // mono input buffer (left channel)
const uint16_t * in_R, // mono input buffer (right channel)
uint16_t * out, // stereo output buffer
const size_t num_samples) // number of samples
{
for (size_t i = 0; i < num_samples; ++i)
{
out[i*2] = in_L[i];
out[i*2+1] = in_R[i];
}
}
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;
char *buffer;
char *stereo;
snd_pcm_format_t format = SND_PCM_FORMAT_S16_LE;
int channels = 2;
/* 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, format);
/* Two channels (stereo) */
snd_pcm_hw_params_set_channels(handle, params, channels);
/* 44100 bits/second sampling rate (CD quality) */
val = 44100;
snd_pcm_hw_params_set_rate_near(handle, params, &val, &dir);
/* Set period size to 32 frames. */
frames = 128;
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);
int width = (snd_pcm_format_width(format)/8);
fprintf(stderr,"Format width: %d\n", width);
size = frames * width; /* 2 bytes/sample, 2 channels */
buffer = (char *) malloc(size);
stereo = (char *) malloc(size*2);
for(int i = 0; i < 2*size; i++){
stereo[i] = 0x00;
}
/* 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);
if (rc == -EPIPE) {
/* EPIPE means overrun */
fprintf(stderr, "overrun occurred\n");
snd_pcm_prepare(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);
}
if(channels > 1){
interleave((uint16_t*)buffer,(uint16_t*)buffer,(uint16_t*)stereo,frames);
write(1, stereo, 2*size);
}
else{
write(1, buffer, size);
}
}
snd_pcm_drain(handle);
snd_pcm_close(handle);
free(buffer);
return 0;
}
回放
/*
This example reads standard from input and writes
to the default PCM device for 5 seconds of data.
*/
/* Use the newer ALSA API */
#define ALSA_PCM_NEW_HW_PARAMS_API
#include <alsa/asoundlib.h>
int main() {
long loops;
int rc;
int size;
snd_pcm_t *handle;
snd_pcm_hw_params_t *params;
unsigned int rate = 44100;
int dir;
snd_pcm_uframes_t frames;
char *buffer;
char* stereo;
snd_pcm_format_t format = SND_PCM_FORMAT_S16_LE;
int channels = 2;
/* Open PCM device for playback. */
rc = snd_pcm_open(&handle, "default",
SND_PCM_STREAM_PLAYBACK, 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, format);
/* Two channels (stereo) */
snd_pcm_hw_params_set_channels(handle, params, channels);
/* 44100 bits/second sampling rate (CD quality) */;
rc = snd_pcm_hw_params_set_rate_near(handle, params, &rate, &dir);
if(rc < 0){
unsigned int r;
snd_pcm_hw_params_get_rate(params, &r, &dir);
fprintf(stderr, "cannot set sample rate, using: %d\n", r);
}
/* Set period size to 32 frames. */
frames = 128;
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 * (snd_pcm_format_width(format)/8) * channels; /* 2 bytes/sample, 2 channels */
buffer = (char *) malloc(size);
stereo = malloc(2*size);
/* We want to loop for 5 seconds */
snd_pcm_hw_params_get_period_time(params, &rate, &dir);
/* 5 seconds in microseconds divided by
* period time */
loops = 5000000 / rate;
while (loops > 0) {
loops--;
rc = read(0, buffer, size);
if (rc == 0) {
fprintf(stderr, "end of file on input\n");
break;
} else if (rc != size) {
fprintf(stderr,
"short read: read %d bytes\n", rc);
}
rc = snd_pcm_writei(handle, buffer, frames);
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));
} else if (rc != (int)frames) {
fprintf(stderr,
"short write, write %d frames\n", rc);
}
}
snd_pcm_drain(handle);
snd_pcm_close(handle);
free(buffer);
return 0;
}
識別低頻噪聲中的短高頻聲音（objc / c）
[英]Recognition of a short high frequency sound in low frequency noise (objc/c)
Function 通過 alsa 輸出聲音在通過 pthread 創建時不起作用創建：沒有聲音，100% CPU 使用率
[英]Function outputting sound through alsa not working when called via pthread create: no sound, 100% CPU usage
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