讀.wav文件 - 不讀標題？

Question

我試圖從.wav文件中讀取標頭信息，我正在閱讀該文件的以下屬性：

    type 
    size
    Format Tag
    Format Length
    Channels
    Sample Rate
    Average Bytes Second
    Block Align
    Bits Per Sample
    Data size

現在，所有內容都讀取完全直到讀取采樣率，然后輸出為“0”值或僅為NULL。

這是代碼:(我打開了文本文件，並將指針傳遞給成員函數）

bool Wav::readHeader(FILE *dataIn)
{
   char type2[4];
   fread(this->type, sizeof(char), 4, dataIn);

   fread(&this->size, sizeof(int), 1, dataIn);

   fread(this->type, sizeof(char), 4, dataIn);

   fread(this->type, sizeof(char), 4, dataIn);

   fread(&this->format_length, sizeof(short), 1, dataIn);

   fread(&this->format_tag, sizeof(short), 1, dataIn);

   fread(&this->channels, sizeof(short), 1, dataIn);


   fread(&this->sample_rate, sizeof(unsigned int), 1, dataIn);

   fread(&this->avg_bytes_sec, sizeof(unsigned short), 1, dataIn);

   fread(&this->block_align, sizeof(short), 1, dataIn);

   fread(&this->bits_per_sample, sizeof(short), 1, dataIn);

   return true;
}

班級成員定義為：

    char type[4]; 
    int size;
    unsigned short format_tag;
    unsigned short format_length;
    unsigned short channels;
    unsigned int sample_rate;
    unsigned short avg_bytes_sec;
    unsigned short block_align;
    unsigned short bits_per_sample;
    unsigned int data_size;

有沒有人有任何解決方案或建議？

（PS道歉，如果這個問題不對。我盡力寫出來！）

Answer 1

如果你有緊密打包的結構代表（PCM）WAVE的標題，它將如下所示：

struct Riff
{
  char chunkId[4]; // "RIFF" (assuming char is 8 bits)
  int chunkSize; // (assuming int is 32 bits)
  char format[4]; // "WAVE"
};

struct Format
{
  char chunkId[4]; // "fmt "
  int chunkSize;
  short format; // assuming short is 16 bits
  short numChannels;
  int sampleRate;
  int byteRate;
  short align;
  short bitsPerSample;
};

struct Data
{
  char chunkId[4]; // "data"
  int chunkSize; // length of data
  char* data;
};

struct Wave // Actual structure of a PCM WAVE file
{
  Riff riffHeader;
  Format formatHeader;
  Data dataHeader;
};

基本上，你的問題是你的代碼中的format_length （我的struct中的Format::chunkSize ）和avg_bytes_sec （我的struct中的Format::byteRate ）每個都是2個字節，但它們每個都應該是4.你也沒有讀取數據subchunk的標題，但我認為這是故意的？

要閱讀，您可以這樣做：

void readWave(std::ifstream& file, Wave& wave)
{
  // First read the RIFF header
  file.read(wave.riffHeader.chunkId,                                   4);
  file.read(reinterpret_cast<char*>(&wave.riffHeader.chunkSize),       4);
  file.read(wave.riffHeader.format,                                    4);

  // Now read the FORMAT header
  file.read(wave.formatHeader.chunkId,                                 4);
  file.read(reinterpret_cast<char*>(&wave.formatHeader.chunkSize),     4);
  file.read(reinterpret_cast<char*>(&wave.formatHeader.format),        2);
  file.read(reinterpret_cast<char*>(&wave.formatHeader.numChannels),   2);
  file.read(reinterpret_cast<char*>(&wave.formatHeader.sampleRate),    4);
  file.read(reinterpret_cast<char*>(&wave.formatHeader.byteRate),      4);
  file.read(reinterpret_cast<char*>(&wave.formatHeader.align),         2);
  file.read(reinterpret_cast<char*>(&wave.formatHeader.bitsPerSample), 2);

  // Now read the DATA header
  file.read(wave.dataHeader.chunkId,                                   4);
  file.read(reinterpret_cast<char*>(&wave.dataHeader.chunkSize),       4);

  // The actual data goes in wave.dataHeader.data, so you can allocate it
  // and then read direclty into it now
}

邁克爾的鏈接是我在需要讀/寫WAVE文件時總是使用的鏈接 （我必須做幾次）。 我建議你仔細閱讀。

如果在“數據”塊之前在WAVE文件中有額外的塊，則此代碼應該能夠跳過它們：

void readWave(std::ifstream& file, Wave& wave)
{
  // First read the RIFF header
  file.read(wave.riffHeader.chunkId,                                   4);
  file.read(reinterpret_cast<char*>(&wave.riffHeader.chunkSize),       4);
  file.read(wave.riffHeader.format,                                    4);

  // Now read the FORMAT header
  file.read(wave.formatHeader.chunkId,                                 4);
  file.read(reinterpret_cast<char*>(&wave.formatHeader.chunkSize),     4);
  file.read(reinterpret_cast<char*>(&wave.formatHeader.format),        2);
  file.read(reinterpret_cast<char*>(&wave.formatHeader.numChannels),   2);
  file.read(reinterpret_cast<char*>(&wave.formatHeader.sampleRate),    4);
  file.read(reinterpret_cast<char*>(&wave.formatHeader.byteRate),      4);
  file.read(reinterpret_cast<char*>(&wave.formatHeader.align),         2);
  file.read(reinterpret_cast<char*>(&wave.formatHeader.bitsPerSample), 2);

  // WAVE files are just a special type of RIFF file, so it's possible
  // there are other chunks, like "fact" chunks. We'll skip over these
  // extra chunks until we find a "data" chunk
  char chunkId[4] = {0};
  int chunkSize = 0;
  while (file.read(chunkId, 4) &&
         (chunkId[0] != 'd' ||
          chunkId[1] != 'a' ||
          chunkId[2] != 't' ||
          chunkId[3] != 'a'))
    {
      file.read(reinterpret_cast<char*>(&chunkSize), 4); // Read the chunk's size
      file.seekg(chunkSize, std::ios_base::cur); // Skip the chunk
    }

  // We've found the DATA chunk and header
  wave.dataHeader.chunkId[0] = chunkId[0];
  wave.dataHeader.chunkId[1] = chunkId[1];
  wave.dataHeader.chunkId[2] = chunkId[2];
  wave.dataHeader.chunkId[3] = chunkId[3];
  file.read(reinterpret_cast<char*>(&wave.dataHeader.chunkSize),       4);

  // The actual data goes in wave.dataHeader.data, so you can allocate it
  // and then read direclty into it now
}