Alsa播放来自CAN FD的音频获取
Alsa播放来自CAN FD的音频获取
提问于 2022-02-17 12:40:48
我正在尝试使用Alsa库复制我从我的CAN FD通讯中获得的音频，进入我的耳机。我不太明白如何正确配置阿尔萨的参数，以便能够听到我从CAN FD获得的声音。
static char *device = "plughw:0,0"; /* playback device */
static snd_pcm_format_t format = SND_PCM_FORMAT_S16_LE; /* sample format */
static unsigned int rate = 16000; /* stream rate */
static unsigned int channels = 1; /* count of channels */
static unsigned int buffer_time = 40000; /* ring buffer length in us */
static unsigned int period_time = 120000; /* period time in us */
static int resample = 1; /* enable alsa-lib resampling */
static int period_event = 0; /* produce poll event after each period */
int size;
while (1) {
do {
nbytes = read(s, &frame, sizeof(struct canfd_frame));
} while (nbytes == 0);
for (x = 0; x < 64; x = x + 2) {
buffer[a] = ((uint32_t) frame.data[x] << 8)
| ((uint32_t) (frame.data[x + 1]));
a++;
}
//err=snd_pcm_writei(handle,buffer,32);
//printf("Datos = %d\n", err);
memcpy(total1 + i * 32, buffer, 32 * sizeof(uint32_t));
i++;
a = 0;
if (i == 500) {
buffer_length=16000;
ptr = total1;
while(buffer_length > 0){
err = snd_pcm_writei(handle, ptr, 16000);
printf("Datos = %d\n", err);
snd_pcm_avail_delay(handle, &availp, &delayp);
//printf("available frames =%ld delay = %ld z = %d\n", availp, delayp, z);
if (err == -EAGAIN)
continue;
if(err < 0){
err=snd_pcm_recover(handle, err, 1);
}
else{
ptr += err * channels;
buffer_length -= err;
z++;
}
if(err<0){
printf("snd_pcm_writei failed: %s\n", snd_strerror(err));
break;
}
}
i = 0;
}这是我的代码的一部分，我不认为张贴整个代码是值得的。我不明白我应该给buffer_time、period_time哪些价值观，以及如何能够实时地听我通过CAN FD获得哪些信息。我正在使用snd_pcm_writei，插入一个缓冲区，填充从CAN FD中获得的一些示例。我不知道我应该给缓冲区和“框架”变量的大小，这是另一个我不太理解的变量，尽管我读了一些关于它的文章。
知道我该如何配置我的系统吗？(buffer_time，period_time，buffer_size，frame，.)我试过使用不同的缓冲区和帧大小，但我想我不明白它是如何正常工作的。如何计算snd_pcm_writei()的帧和缓冲区的大小，以便实时侦听音频？
我应该使用两个不同的线程吗？一个用来创建带有CAN FD信息的缓冲区，另一个用来处理缓冲区和音频输出？
事先谢谢你，安德。
回答 1
Stack Overflow用户
回答已采纳
发布于 2022-02-22 11:02:54
我终于通过耳机听到了自己的声音。我已经改变了我以前发布的配置，以便将它与我从CAN FD中获得的数据结合起来。我将在这里张贴我的部分代码，以防有人需要一个例子。像这样处理缓冲区的最重要的部分是处理填充时间和通信时间。因此，处理时间和配置Alsa参数可以更容易地处理缓冲区。
static char *device = "plughw:0,0"; /* playback device */
static snd_pcm_format_t format = SND_PCM_FORMAT_S16_LE; /* sample format */
static unsigned int rate = 22000; /* stream rate */
static unsigned int channels = 1; /* count of channels */
static unsigned int buffer_time = 1000; /* ring buffer length in us */
static unsigned int period_time = 10000; /* period time in us */
static int resample = 1; /* enable alsa-lib resampling */
static int period_event = 0; /* produce poll event after each period */
int size;
static snd_pcm_sframes_t buffer_size;
static snd_pcm_sframes_t period_size;
static snd_output_t *output = NULL;
snd_pcm_sframes_t delayp;
snd_pcm_sframes_t availp;
snd_pcm_uframes_t frames;
static void write_loop(snd_pcm_t *handle) {
uint32_t *buffer = malloc(16000 * sizeof(uint32_t));
uint32_t *total1 = malloc(16000 * sizeof(uint32_t)); // array to hold the result
while (1) {
do {
nbytes = read(s, &frame, sizeof(struct canfd_frame));
} while (nbytes == 0);
for (x = 0; x < 64;x = x + 2) {
buffer[a] = ((uint32_t) frame.data[x] << 8)
| ((uint32_t) (frame.data[x + 1]));
//buffer[a]=frame.data[x];
a++;
}
i++;
if (i == 250) {
memcpy(total1, buffer, 16000 * sizeof(uint32_t));
//printf("Address = %lu \n",(unsigned long)total1);
flag = 1;
buffer_length = 16000;
i = 0;
a = 0;
}
if (flag == 1) {
while(buffer_length > 0) {
snd_pcm_prepare(handle);
err = snd_pcm_writei(handle, total1, buffer_length);
//printf("Datos = %d\n", err);
snd_pcm_avail_delay(handle, &availp, &delayp);
//printf("available frames =%ld delay = %ld\n",availp,delayp);
if (err == -EAGAIN)
continue;
if (err < 0) {
err = snd_pcm_recover(handle, err, 1);
} else {
ptr += err * channels;
buffer_length -= err;
z++;
}
if (err < 0) {
printf("snd_pcm_writei failed: %s\n", snd_strerror(err));
break;
}
}
flag = 0;
}
}
}页面原文内容由Stack Overflow提供。腾讯云小微IT领域专用引擎提供翻译支持
原文链接：
https://stackoverflow.com/questions/71158323
复制相关文章
相似问题
腾讯云开发者
