Question

我正在尝试更改.wav文件头中与文件大小相对应的字节，即第4个和第40个字节。目前，我正在将整个标头复制到缓冲区，尝试在那里编辑它，然后将其写入目标文件，但它似乎不起作用。

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

    int delay = atoi(argv[1]);
    FILE * source = fopen(argv[2], "rb");
    FILE * destination = fopen(argv[3], "wb");

    void * header = malloc(44); // size of a wav file header
    fread(header, sizeof(header), 1, source);

    // my attempt at changing the 4nd and 40th bytes
    sizeptr1 = (unsigned int *)(header + 4);
    sizeptr2 = (unsigned int *)(header + 40);
    *sizeptr1 = *sizeptr1 + delay;
    *sizeptr2 = *sizeptr2 + delay
    fwrite(header, sizeof(header), 1, destination);

    return 0;
}

更改这些字节并将新标头写入输出文件的最有效方法是什么？

Answer 1

如果您确定要更改哪些字节，则字节数组最简单。例如，第4个字节位于buffer[3]。

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

#define BUFFSIZE    1024
#define HEADSIZE    44

int main(int argc, char * argv []) {
    int delay;
    size_t bytes;
    FILE * source = NULL;
    FILE * destination = NULL;
    unsigned char buffer[BUFFSIZE];

    if (argc < 4) return 0;         // check enough args
    delay = atoi(argv[1]);
    if (NULL == (source = fopen(argv[2], "rb")))
        return 0;
    if (NULL == (destination = fopen(argv[3], "wb")))
        return 0;

    // copy & alter buffer
    if (HEADSIZE != fread(buffer, 1, HEADSIZE, source))
        return 0;
    buffer[4] = delay;
    buffer[40] = delay;
    if (HEADSIZE != fwrite(buffer, 1, HEADSIZE, destination))
        return 0;

    // copy rest of file
    while ((bytes = fread(buffer, 1, BUFFSIZE, source)) != 0) {
        if (bytes != fwrite(buffer, 1, bytes, destination))
            return 0;
    }
    if (0 == fclose(destination))
        printf("Success\n");
    fclose (source);
    return 0;
}

Answer 2

这是编辑文件中字节的一种方法，检查它是否适合您。

int
ChangeHeaderByte(
        const char* fileName,
        unsigned int pos[],
        unsigned int val[],
        unsigned int size
        )
{
  unsigned int i = 0;
  unsigned int temp = 0;
  FILE * fileHandle = fopen(fileName, "r+");
  if (fileHandle == 0) {
    fprintf(stderr,"Error: %s : %d : Failed to open file ' %s '\n",
            __func__,__LINE__,fileName);
    return (1);
  }
  for ( i = 0; i < size ; ++i )
  {
    if ( fseek(fileHandle, pos[i] - (unsigned int)1, SEEK_SET) == 0 )
    {
      if ( fread(&temp,sizeof(unsigned int),1,fileHandle) == 1 )
      {
         if ( fseek(fileHandle, pos[i] - (unsigned int)1 , SEEK_SET) == 0 )
         {
             val[i] += temp;
             fwrite(&val[i], sizeof(unsigned int), 1, fileHandle);
         }
         else
         {
             fprintf(stderr,"Error: %s : %d : fseek() failed on file ' %s '\n",
                     __func__,__LINE__,fileName);
             return (1);
         }
      }
      else
      {
          fprintf(stderr,"Error: %s : %d : fread() failed on file ' %s '\n",
                  __func__,__LINE__,fileName);
          return (1);
      }
    } else {
      fprintf(stderr,"Error: %s : %d : fseek() failed on file ' %s '\n",
              __func__,__LINE__,fileName);
      return (1);
    }
  }
  fclose(fileHandle);
  return (0);
}

int main(void)
{
  const unsigned int size = 2;
  char fileName[] = "C:\\Users\\sridhar\\test\\test.wav";
  unsigned int pos[2] = { 4 , 40 };
  unsigned int val[2] = { 123456, 123456 };

  ChangeHeaderByte(fileName,pos,val,size);
  return 0;
}

创建输出文件时更改.wav文件头中的字节

2 个答案: