简易重采样resampler的实现

基于开源库speexdsp， 可以简单实现重采样。

 

简单实现的代码如下：

需要的三方库： speexdsp ,libsndfile

#include <stdlib.h>
#include <sndfile.h>
#include <speex_resampler.h>

#define BUFFER_SIZE 2048

int main(int argv, const char *args[]) {
    if (argv != 4) {
        printf("usage: %s <input file path> <to samplerate> <output file path> \n", args[0]);
        return 1;
    }

    const char *in_path = args[1];

    int output_sr = atoi(args[2]);
    const char *out_path = args[3];

    SF_INFO info;
    SNDFILE *in = sf_open(in_path, SFM_READ, &info);
    if (!in) {
        fprintf(stderr, "cannot open file %s\n", in_path);
        return 2;
    }
    SF_INFO onfo;
    onfo.channels = 1;
    onfo.samplerate = output_sr;
    onfo.format = SF_FORMAT_WAV | SF_FORMAT_PCM_16 ;
    onfo.sections = 0;
    onfo.seekable = 1;
    SNDFILE *out = sf_open(out_path, SFM_WRITE, &onfo);
    if (!out) {
        fprintf(stderr, "cannot open file %s\n", out_path);
        sf_close(in);
        return 2;
    }


    int err = 0;
    SpeexResamplerState *resampler = speex_resampler_init(info.channels, info.samplerate, output_sr, 1, &err);

    printf("=====================\nchannels: %d\nsample rate:%d\n", info.channels, info.samplerate);
    if (info.channels != 1) {
        fprintf(stderr, "only support mono wav.\n");
        sf_close(in);
        sf_close(out);
        return 3;
    }

    short in_buffer[BUFFER_SIZE] = {0};
    uint32_t size = BUFFER_SIZE * output_sr/ info.samplerate;
    printf("new buffer size: %d\n", size);
    short *out_buffer = (short *) calloc(size,  sizeof(short));
    uint32_t read = 0;
    do {
        read = sf_read_short(in, in_buffer, BUFFER_SIZE);

        err = speex_resampler_process_int(resampler, 0, (const spx_int16_t *)in_buffer, (spx_uint32_t *)&read, (spx_int16_t *)out_buffer, &size);
        if (err) {
            fprintf(stderr, "err:%d\n", err);
        }
        sf_write_short(out, out_buffer, size);
    } while(read>0);
    free(out_buffer);
    sf_close(in);
    sf_close(out);
    return 0;
}

上述代码只在centos上编译测试，不过后来也有移植到windows下的。

如果需要成品的可以在这里下载windows版本，有需要可以自取。

https://download.youkuaiyun.com/download/mimiduck/12465600