voice_broadcast/audio_play.c

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

void check_and_set_max_volume()
{
    FILE *fp;
    char buffer[256];
    int volume_left = -1;
    int speaker_on = 0;

    // 检查 PCM 音量
    fp = popen("amixer get PCM | grep 'Front Left'", "r");
    if (fp)
    {
        while (fgets(buffer, sizeof(buffer), fp))
        {
            if (sscanf(buffer, "  Front Left: %d", &volume_left) == 1)
            {
                break;
            }
        }
        pclose(fp);
    }

    if (volume_left == -1)
    {
        printf("无法获取音量信息\n");
    }
    else if (volume_left < 192)
    {
        printf("当前音量为 %d，设置为最大...\n", volume_left);
        system("amixer set PCM 192");
    }
    else
    {
        printf("音量已是最大（%d）\n", volume_left);
    }

    // 检查扬声器是否开启
    fp = popen("amixer get Speaker | grep 'Mono:'", "r");
    if (fp)
    {
        while (fgets(buffer, sizeof(buffer), fp))
        {
            if (strstr(buffer, "[on]"))
            {
                speaker_on = 1;
                break;
            }
        }
        pclose(fp);
    }

    if (!speaker_on)
    {
        printf("扬声器未打开，正在开启...\n");
        system("amixer set Speaker unmute");
    }
    else
    {
        printf("扬声器已开启\n");
    }
}

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

    const char *device = "hw:0,0";    // 要使用的 ALSA 设备
    const char *filename = "001.wav"; // WAV 文件路径
    snd_pcm_t *pcm_handle;
    snd_pcm_hw_params_t *params;
    unsigned int sample_rate = 44100; // 采样率（需与 WAV 文件一致）
    int pcm, dir;
    snd_pcm_uframes_t frames;
    FILE *file;
    char *buffer;
    int buffer_size;

    // 打开音频文件
    file = fopen(filename, "rb");
    if (!file)
    {
        perror("Unable to open audio file");
        return 1;
    }

    // 跳过标准 WAV 头部（44 字节），如果你的音频文件已经是纯 PCM 数据可以注释掉此行
    fseek(file, 44, SEEK_SET);

    // 打开 PCM 设备
    if ((pcm = snd_pcm_open(&pcm_handle, device, SND_PCM_STREAM_PLAYBACK, 0)) < 0)
    {
        fprintf(stderr, "Unable to open PCM device %s: %s\n", device, snd_strerror(pcm));
        fclose(file);
        return 1;
    }

    // 分配并初始化硬件参数对象
    snd_pcm_hw_params_alloca(&params);
    snd_pcm_hw_params_any(pcm_handle, params);
    snd_pcm_hw_params_set_access(pcm_handle, params, SND_PCM_ACCESS_RW_INTERLEAVED);
    snd_pcm_hw_params_set_format(pcm_handle, params, SND_PCM_FORMAT_S16_LE);
    snd_pcm_hw_params_set_channels(pcm_handle, params, 2);
    snd_pcm_hw_params_set_rate_near(pcm_handle, params, &sample_rate, &dir);

    // 应用硬件参数
    if ((pcm = snd_pcm_hw_params(pcm_handle, params)) < 0)
    {
        fprintf(stderr, "Unable to set hardware parameters: %s\n", snd_strerror(pcm));
        snd_pcm_close(pcm_handle);
        fclose(file);
        return 1;
    }

    // 获取每个周期（period）的帧数，并据此计算缓冲区大小
    snd_pcm_hw_params_get_period_size(params, &frames, &dir);
    buffer_size = frames * 2 /*bytes per sample*/ * 2 /*channels*/;
    buffer = (char *)malloc(buffer_size);
    if (!buffer)
    {
        fprintf(stderr, "Unable to allocate buffer\n");
        snd_pcm_close(pcm_handle);
        fclose(file);
        return 1;
    }

    // 无限循环播放
    while (1)
    {
        size_t bytes_read = fread(buffer, 1, buffer_size, file);
        if (bytes_read == 0)
        {
            // 已经读到文件末尾，重新回到数据区的起始位置（跳过头部）
            fseek(file, 44, SEEK_SET);
            continue;
        }

        // 计算本次要写入的“帧”数，如果最后一块数据不足一个完整周期，按实际读到的字节数计算
        snd_pcm_uframes_t frames_to_deliver = bytes_read / (2 * 2);

        // 写入 PCM
        int ret = snd_pcm_writei(pcm_handle, buffer, frames_to_deliver);
        if (ret == -EPIPE)
        {
            // 缓冲区下溢，重启 PCM 设备
            snd_pcm_prepare(pcm_handle);
        }
        else if (ret < 0)
        {
            fprintf(stderr, "Playback error: %s\n", snd_strerror(ret));
        }
        // 如果写入的帧数小于需要的，可以在这里处理（可选）
    }

    // 下面的代码理论上永远不会执行到，但为了完整性保留
    free(buffer);
    snd_pcm_drain(pcm_handle);
    snd_pcm_close(pcm_handle);
    fclose(file);

    return 0;
}