我正在处理wav文件的幅度并按一些小数因子缩放它.我试图以有效记忆的方式阅读和重写文件,同时也试图解决语言的细微差别(我是C的新手).该文件可以是8位或16位格式.我想这样做的方法是首先将

header data读入一些预定义的结构,然后在一个循环中处理实际数据,在那里我将一大块数据读入缓冲区,做任何需要它,以及然后将其写入输出.

#include

#include

typedef struct header

{

char chunk_id[4];

int chunk_size;

char format[4];

char subchunk1_id[4];

int subchunk1_size;

short int audio_format;

short int num_channels;

int sample_rate;

int byte_rate;

short int block_align;

short int bits_per_sample;

short int extra_param_size;

char subchunk2_id[4];

int subchunk2_size;

} header;

typedef struct header* header_p;

void scale_wav_file(char * input,float factor,int is_8bit)

{

FILE * infile = fopen(input,"rb");

FILE * outfile = fopen("outfile.wav","wb");

int BUFSIZE = 4000,i,MAX_8BIT_AMP = 255,MAX_16BIT_AMP = 32678;

// used for processing 8-bit file

unsigned char inbuff8[BUFSIZE],outbuff8[BUFSIZE];

// used for processing 16-bit file

short int inbuff16[BUFSIZE],outbuff16[BUFSIZE];

// header_p points to a header struct that contains the file's Metadata fields

header_p Meta = (header_p)malloc(sizeof(header));

if (infile)

{

// read and write header data

fread(Meta,1,sizeof(header),infile);

fwrite(Meta,sizeof(Meta),outfile);

while (!feof(infile))

{

if (is_8bit)

{

fread(inbuff8,BUFSIZE,infile);

} else {

fread(inbuff16,infile);

}

// scale amplitude for 8/16 bits

for (i=0; i < BUFSIZE; ++i)

{

if (is_8bit)

{

outbuff8[i] = factor * inbuff8[i];

if ((int)outbuff8[i] > MAX_8BIT_AMP)

{

outbuff8[i] = MAX_8BIT_AMP;

}

} else {

outbuff16[i] = factor * inbuff16[i];

if ((int)outbuff16[i] > MAX_16BIT_AMP)

{

outbuff16[i] = MAX_16BIT_AMP;

} else if ((int)outbuff16[i] < -MAX_16BIT_AMP) {

outbuff16[i] = -MAX_16BIT_AMP;

}

}

}

// write to output file for 8/16 bit

if (is_8bit)

{

fwrite(outbuff8,outfile);

} else {

fwrite(outbuff16,outfile);

}

}

}

// cleanup

if (infile) { fclose(infile); }

if (outfile) { fclose(outfile); }

if (Meta) { free(Meta); }

}

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

{

char infile[] = "file.wav";

float factor = 0.5;

scale_wav_file(infile,factor,0);

return 0;

}

我在最后得到不同的文件大小(对于40Mb文件大约1k左右),我怀疑这是因为我正在向输出写入整个缓冲区,即使文件可能已终止在填充整个缓冲区大小之前.此外,输出文件搞砸了 – 不会播放或打开 – 所以我可能做错了.关于我搞砸的地方的任何提示都会很棒.谢谢！