在C WAV头的打印 [英] printing of a wav header in c

问题描述

您好，我有这个code采取作为输入一个wav文件，然后把华包头到一个结构，然后输出。一切都只是AudioFormat的和numChannels不错，但我不明白why.For例如，它应该输出AudioFormat的：1和numChannels：2，但它输出AudioFormat的：0和numChannels：1。我不明白为什么会这样。

  typedef结构wavHeader
{
    字节chunckID [4];
    DWORD chunckSize;
    字节格式[4];
    字节subchunk1ID [4];
    字subchunk1Size;
    字AudioFormat的;
    字numChannels;
    DWORD采样率;
    DWORD byteRate;
    字blockAlign;
    字bitsPerSample;
    字节subchunk2ID [4];
    DWORD subchunk2Size;
} wav_header;INT check_file_name（字符*文件名）;空列表（字符数组**）//的argv
{
    wav_header wavHeader;
    FILE * PFILE;
    如果（check_file_name（数组[2]）== 0）
    {
        的printf（错误的文件名\\ n）;
        出口（1）;
    }
    PFILE = FOPEN（数组[2]，R）;
    如果（PFILE！= NULL）
    {
        FREAD（安培; wavHeader，sizeof的（wav_header），1，PFILE）;
        FCLOSE（PFILE）;
        的printf（ChunkID： %c%c%c%c\
\",wavHeader.chunckID[0],wavHeader.chunckID[1],wavHeader.chunckID[2],wavHeader.chunckID[3]);
        的printf（CHUNKSIZE数：％d \\ n，wavHeader.chunckSize）;
        的printf（格式：％C％C％C％C \\ N，wavHeader.format [0]，wavHeader.format [1]，wavHeader.format [2]，wavHeader.format [3]）;
        的printf（SubChunk1ID： %c%c%c%c\
\",wavHeader.subchunk1ID[0],wavHeader.subchunk1ID[1],wavHeader.subchunk1ID[2],wavHeader.subchunk1ID[3]);
        的printf（Subchunk1Size数：％d \\ n，wavHeader.subchunk1Size）;
        的printf（AudioFormat的数：％d \\ n，wavHeader.audioFormat）;
        的printf（NumChannels数：％d \\ n，wavHeader.numChannels）;
        的printf（采样率：％d个\\ N，wavHeader.sampleRate）;
        的printf（ByteRate数：％d \\ n，wavHeader.byteRate）;
        的printf（BlockAlign数：％d \\ n，wavHeader.blockAlign）;
        的printf（BitsPerSample数：％d \\ n，wavHeader.bitsPerSample）;
        的printf（Subchunk2ID： %c%c%c%c\
\",wavHeader.subchunk2ID[0],wavHeader.subchunk2ID[1],wavHeader.subchunk2ID[2],wavHeader.subchunk2ID[3]);
        的printf（Subchunk2Size数：％d \\ n，wavHeader.subchunk2Size）;
    }
    其他
    {
        的printf（此文件不退出\\ n）;
        出口（1）;
    }
}
 

解决方案

subchunk1Size 应该是 DWORD ，不一个字（见的 http://www-mmsp.ece.mcgill.ca/Documents/AudioFormats/WAVE/WAVE.html 例如）。您的其他块大小是否正确声明。

由于 DJF指出你还需要指定包装和担心字节顺序。该WAV标头是16位的包装，和little-endian。随着 GCC ，我preFER使用的#pragma包（推，2）结构声明之前，和的#pragma包（POP）之后。如果你的#include＆LT; endian.h＆GT; 您可以使用 le32toh 和 le16toh 阅读（及其对应 htole32 和 htole16 写）。

Hi i have this code for taking as input a wav file and then putting the wah header into a struct and then output it. Everything is good except audioFormat and numChannels but i can't understand why.For example it should output audioFormat: 1 and numChannels: 2 but it outputs audioFormat:0 and numChannels: 1 . I can't understand why this happens.

typedef struct wavHeader
{
    byte chunckID[4];
    dword chunckSize;
    byte format[4];
    byte subchunk1ID[4];
    word subchunk1Size;
    word audioFormat;
    word numChannels;
    dword sampleRate;
    dword byteRate;
    word blockAlign;
    word bitsPerSample;
    byte subchunk2ID[4];
    dword subchunk2Size;
}wav_header;

int check_file_name(char *filename);

void list(char **array) //argv
{
    wav_header wavHeader;
    FILE *pFile;
    if(check_file_name(array[2]) == 0)
    {
        printf("wrong file name\n");
        exit(1);
    }
    pFile = fopen (array[2] ,"r");
    if( pFile != NULL)
    {
        fread(&wavHeader, sizeof(wav_header), 1, pFile);
        fclose(pFile);
        printf("ChunkID: %c%c%c%c\n",wavHeader.chunckID[0],wavHeader.chunckID[1],wavHeader.chunckID[2],wavHeader.chunckID[3]);
        printf("ChunkSize: %d\n",wavHeader.chunckSize);
        printf("Format: %c%c%c%c\n",wavHeader.format[0],wavHeader.format[1],wavHeader.format[2],wavHeader.format[3]);
        printf("SubChunk1ID: %c%c%c%c\n",wavHeader.subchunk1ID[0],wavHeader.subchunk1ID[1],wavHeader.subchunk1ID[2],wavHeader.subchunk1ID[3]);
        printf("Subchunk1Size: %d\n",wavHeader.subchunk1Size);
        printf("AudioFormat: %d\n",wavHeader.audioFormat);
        printf("NumChannels: %d\n",wavHeader.numChannels); 
        printf("SampleRate: %d\n",wavHeader.sampleRate);
        printf("ByteRate: %d\n",wavHeader.byteRate);     
        printf("BlockAlign: %d\n",wavHeader.blockAlign);   
        printf("BitsPerSample: %d\n",wavHeader.bitsPerSample);
        printf("Subchunk2ID: %c%c%c%c\n",wavHeader.subchunk2ID[0],wavHeader.subchunk2ID[1],wavHeader.subchunk2ID[2],wavHeader.subchunk2ID[3]);
        printf("Subchunk2Size: %d\n",wavHeader.subchunk2Size);
    }
    else
    {
        printf("This file doesn't exit\n");
        exit(1);
    }
}

解决方案

subchunk1Size should be a dword, not a word (see http://www-mmsp.ece.mcgill.ca/Documents/AudioFormats/WAVE/WAVE.html for instance). Your other chunk sizes are declared correctly.

As djf points out you also need to specify the packing and worry about endianness. The WAV header is 16-bit packed, and little-endian. With gcc, I prefer to use #pragma pack(push, 2) before the struct declaration, and #pragma pack(pop) after. And if you #include <endian.h> you can use le32toh and le16toh to read (and their counterparts htole32 and htole16 to write).

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