audio - 使用 ALSA 的音频捕获浮点格式 - 无法设置格式

Question

我正在尝试使用 Alsa 和 c/c++ 库来捕获音频。我可以使用 16 位和 32 位Int成功地做到这一点，但是当我尝试使用浮点格式时，我无法设置相应的格式。

示例：//返回 -22 并且不起作用 err = snd_pcm_hw_params_set_format (capture_handle, hw_params, SND_PCM_FORMAT_FLOAT));

//返回 0 并按预期工作。错误 = snd_pcm_hw_params_set_format (capture_handle, hw_params, SND_PCM_FORMAT_S32));

我一直在寻找很长一段时间，但我根本没有找到这个问题的答案。

先感谢您！

完整代码：

#include <stdio.h>

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

int main(int argc, char *argv[]) {

int i;
int err;
char *buffer;
int buffer_frames = 128;
unsigned int rate = 44100;
snd_pcm_t *capture_handle;
snd_pcm_hw_params_t *hw_params;

snd_pcm_format_t format = SND_PCM_FORMAT_FLOAT;
//snd_pcm_format_t format = SND_PCM_FORMAT_S32;

if ((err = snd_pcm_open(&capture_handle, "hw:0", SND_PCM_STREAM_CAPTURE, 0)) < 0) {
    fprintf(stderr, "cannot open audio device %s (%s)\n",
            argv[1],
            snd_strerror(err));
    exit(1);
}

fprintf(stdout, "audio interface opened\n");

if ((err = snd_pcm_hw_params_malloc(&hw_params)) < 0) {
    fprintf(stderr, "cannot allocate hardware parameter structure (%s)\n",
            snd_strerror(err));
    exit(1);
}

fprintf(stdout, "hw_params allocated\n");

if ((err = snd_pcm_hw_params_any(capture_handle, hw_params)) < 0) {
    fprintf(stderr, "cannot initialize hardware parameter structure (%s)\n",
            snd_strerror(err));
    exit(1);
}

fprintf(stdout, "hw_params initialized\n");

if ((err = snd_pcm_hw_params_set_access(capture_handle, hw_params, SND_PCM_ACCESS_RW_INTERLEAVED)) < 0) {
    fprintf(stderr, "cannot set access type (%s)\n",
            snd_strerror(err));
    exit(1);
}

fprintf(stdout, "hw_params access setted\n");

if ((err = snd_pcm_hw_params_set_format(capture_handle, hw_params, format)) < 0) {
    fprintf(stderr, "cannot set sample format (%s)\n",
            snd_strerror(err));
    exit(1);
}

fprintf(stdout, "hw_params format setted\n");

if ((err = snd_pcm_hw_params_set_rate_near(capture_handle, hw_params, &rate, 0)) < 0) {
    fprintf(stderr, "cannot set sample rate (%s)\n",
            snd_strerror(err));
    exit(1);
}

fprintf(stdout, "hw_params rate setted\n");

if ((err = snd_pcm_hw_params_set_channels(capture_handle, hw_params, 2)) < 0) {
    fprintf(stderr, "cannot set channel count (%s)\n",
            snd_strerror(err));
    exit(1);
}

fprintf(stdout, "hw_params channels setted\n");

if ((err = snd_pcm_hw_params(capture_handle, hw_params)) < 0) {
    fprintf(stderr, "cannot set parameters (%s)\n",
            snd_strerror(err));
    exit(1);
}

fprintf(stdout, "hw_params setted\n");

snd_pcm_hw_params_free(hw_params);

fprintf(stdout, "hw_params freed\n");

if ((err = snd_pcm_prepare(capture_handle)) < 0) {
    fprintf(stderr, "cannot prepare audio interface for use (%s)\n",
            snd_strerror(err));
    exit(1);
}

fprintf(stdout, "audio interface prepared\n");

buffer = (char*) malloc(128 * snd_pcm_format_width(format) / 8 * 2);

fprintf(stdout, "buffer allocated %d\n", snd_pcm_format_width(format) / 8 * 2);
int fd = open("in.pcm", O_CREAT | O_RDWR, 0666);
//for (i = 0; i < 10; ++i) {
i = 0;
while (++i) {
    //snd_pcm_wait(capture_handle, 1000);
    if ((err = snd_pcm_readi(capture_handle, buffer, buffer_frames)) != buffer_frames) {
        fprintf(stderr, "read from audio interface failed (%s)\n",
                snd_strerror(err));
        exit(1);
    }
    write(fd, buffer, 128 * snd_pcm_format_width(format) / 8 * 2);
    //fprintf(stdout, "read %d done\n", i);
}
close(fd);

free(buffer);

fprintf(stdout, "buffer freed\n");

snd_pcm_close(capture_handle);
fprintf(stdout, "audio interface closed\n");

exit(0);

}

标签： audioformatalsapcm