使用C ++中的libmad库将24 khz的mp3音频转换为16 khz的wav？

#include <mad.h>

void convertMP3toWAV(const char* mp3File, const char* wavFile) {
    FILE* mp3 = fopen(mp3File, "rb");
    FILE* wav = fopen(wavFile, "wb");

    // 初始化libmad解码器
    struct mad_stream stream;
    struct mad_frame frame;
    struct mad_synth synth;
    mad_stream_init(&stream);
    mad_frame_init(&frame);
    mad_synth_init(&synth);

    // 设置输入流
    mad_stream_buffer(&stream, mp3, BUFSIZ);

    // 设置输出流
    // 这里假设目标音频为16 kHz的WAV文件
    int sampleRate = 16000;
    int numChannels = 1; // 单声道
    int bitsPerSample = 16;
    int byteRate = sampleRate * numChannels * (bitsPerSample / 8);
    int blockAlign = numChannels * (bitsPerSample / 8);
    fwrite("RIFF", 1, 4, wav);
    fwrite("\0\0\0\0", 1, 4, wav); // 先占位，待后续填充
    fwrite("WAVEfmt ", 1, 8, wav);
    fwrite("\20\0\0\0", 1, 4, wav); // PCM格式
    fwrite("\1\0", 1, 2, wav); // 单声道
    fwrite(&numChannels, 1, 2, wav);
    fwrite(&sampleRate, 1, 4, wav);
    fwrite(&byteRate, 1, 4, wav);
    fwrite(&blockAlign, 1, 2, wav);
    fwrite(&bitsPerSample, 1, 2, wav);
    fwrite("data", 1, 4, wav);
    fwrite("\0\0\0\0", 1, 4, wav); // 先占位，待后续填充

    // 解码并转换音频
    while (mad_frame_decode(&frame, &stream) == 0) {
        mad_synth_frame(&synth, &frame);
        mad_fixed_t const* left_ch = synth.pcm.samples[0];
        mad_fixed_t const* right_ch = synth.pcm.samples[1];

        for (unsigned int i = 0; i < synth.pcm.length; i++) {
            mad_fixed_t sample = mad_f_divide(left_ch[i], MAD_F_ONE);
            mad_fixed_t scaled = mad_f_multiply(sample, MAD_F_ONE);
            mad_fixed_t rounded = mad_f_todouble(scaled);
            mad_fixed_t clamped = mad_f_clip(rounded, -32767, 32767);
            mad_fixed_t offset = mad_f_add(clamped, MAD_F_ONE);
            mad_fixed_t shifted = mad_f_multiply(offset, MAD_F_ONE_HALF);
            mad_fixed_t quantized = mad_f_todouble(shifted);
            int16_t pcm_sample = quantized;

            fwrite(&pcm_sample, 1, sizeof(pcm_sample), wav);
        }
    }

    // 清理资源
    mad_synth_finish(&synth);
    mad_frame_finish(&frame);
    mad_stream_finish(&stream);

    // 填充WAV文件头信息
    fseek(wav, 4, SEEK_SET);
    uint32_t fileSize = ftell(wav) - 8;
    fwrite(&fileSize, 1, 4, wav);
    fseek(wav, 40, SEEK_SET);
    uint32_t dataSize = ftell(wav) - 44;
    fwrite(&dataSize, 1, 4, wav);

    // 关闭文件
    fclose(mp3);
    fclose(wav);
}

int main() {
    const char* mp3File = "input.mp3";
    const char* wavFile = "output.wav";
    convertMP3toWAV(mp3File, wavFile);
    return 0;
}