FFmpeg开发笔记（五十八）把32位采样的MP3转换为16位的PCM音频

ffmpeg -i night.mp3 -ar 16000 -ac 1 -acodec pcm_s16le night.pcm

pcm_s16le codec not supported

ffmpeg -encoders | grep pcm

A....D pcm_s16le            PCM signed 16-bit little-endian

ffmpeg -i night.mp3 -ar 16000 -ac 1 -acodec pcm_f32le -f f32le night.pcm

#include <stdio.h>
#include <stdlib.h>
#include <math.h>

int pcm32_to_pcm16(const char *filename)
{  
    FILE *fp =  fopen(filename, "rb");
    FILE *fp1 = fopen("output_16.pcm", "wb");
    unsigned char *sample = (unsigned char*)calloc(1, 4+1);
    while(!feof(fp))
    {
        fread(sample, 4, 1, fp);
        sample[4] = '\0';
        float *sample32 = (float*)sample;
        short sample16 = (short)floor( (*sample32) * 32767 );
        fwrite(&sample16, 2, 1, fp1);
    }
    free(sample);
    fclose(fp);
    fclose(fp1);
    return 0;  
}

int main(int argc, char **argv) {
    const char *src_name = "night.pcm";
    if (argc > 1) {
        src_name = argv[1];
    }
    pcm32_to_pcm16(src_name);
}

gcc convertpcm.c -o convertpcm 

./convertpcm night.pcm