I use a struct for reading Wav-Files in audio format 3 (=IEEE FLOAT 32 Bit) with a 58 byte wav-header. The problem: Byte 38 starts with the "fact" chunk. This seems to be ok. DwFactSize should have an offset of 42. Here the problem begins! The offset is 44 !!! First I thought, the problem is in padding bits. So I tried uints, unsigned chars and attribute((packed)). This doesn't change anything.
This is the definition of the wav header:
0 - 3 'RIFF'/'RIFX' Little/Big-endian
4 - 7 wRiffLength length of file minus the 8 byte riff header
8 - 11 'WAVE'
12 - 15 'fmt '
16 - 19 wFmtSize length of format chunk minus 8 byte header
20 - 21 wFormatTag identifies PCM, ULAW etc
22 - 23 wChannels
24 - 27 dwSamplesPerSecond samples per second per channel
28 - 31 dwAvgBytesPerSec non-trivial for compressed formats
32 - 33 wBlockAlign basic block size
34 - 35 wBitsPerSample non-trivial for compressed formats
(until byte 35 like the usual 44 byte header)
36 - 37 wExtSize = 0 the length of the format extension
38 - 41 'fact'
42 - 45 dwFactSize = 4 length of the fact chunk minus 8 byte header
46 - 49 dwSamplesWritten actual number of samples written out
50 - 53 'data'
54 - 57 dwDataLength length of data chunk minus 8 byte header
output:
...
until here ... correct...
Fact[4] 38
!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
DwFactSize 44
dwSamplesWritten 48
Data[4] 52
dwDataLength 56
Quick hack to show the offset problem:
#include <stdio.h>
#include <stdint.h>
#include <stdlib.h>
#include <cstring>
#include <iostream>
#include <cstddef>
typedef struct WAV_HEADER
{
unsigned char RIFF[4]; /* RIFF Header */ //Magic header
unsigned long ChunkSize; /* RIFF Chunk Size */
unsigned char WAVE[4]; /* WAVE Header */
unsigned char fmt[4]; /* FMT header */
unsigned long Subchunk1Size; /* Size of the fmt chunk: 16=PCM, 18=IEEE Float, 40=Extensible */
unsigned short AudioFormat; /* Audio format 1=PCM, 3=IEEE Float, 6=mulaw,7=alaw, 257=IBM Mu-Law, 258=IBM A-Law, 259=ADPCM, 65534=Extensible */
unsigned short NumOfChan; /* Number of channels 1=Mono 2=Stereo */
unsigned long SamplesPerSec; /* Sampling Frequency in Hz */
unsigned long bytesPerSec; /* bytes per second */
unsigned short blockAlign; /* 2=16-bit mono, 4=16-bit stereo , 6=24-bit stereo,8=32-bit stereo*/
unsigned short bitsPerSample; /* Number of bits per sample, inkl. hier=36 bytes */
unsigned short wExtSize; /* 2 byte, wExtSize = 0 the length of the format extension */
unsigned char Fact[4]; /* "fact" string */
/*Problem here! -> +2bytes*/
unsigned long DwFactSize; /* Sampled data length, inkl. hier bei 44 bytes */
unsigned long dwSamplesWritten;
unsigned char Data[4]; /* leerer string falls extensible -> Beginn nicht nach 44 sondern 68! */
unsigned long dwDataLength; /* raw DataLength */
}__attribute__((packed)) wav_hdr;
int getFileSize(FILE *inFile);
int main(int argc,char *argv[])
{
char *file;
file = argv[1];
wav_hdr wavHeader;
FILE *wavFile;
int headerSize = sizeof(wav_hdr),filelength = 0;
wavFile = fopen(file,"r");
if(wavFile == NULL)
{
printf("\nCan not open wave file. Usage: program [file] \n");
exit(EXIT_FAILURE);
}
fread(&wavHeader,headerSize,1,wavFile);
filelength = getFileSize(wavFile);
fclose(wavFile);
std::cout << "\nRIFF " << offsetof(WAV_HEADER, RIFF) << std::endl;
std::cout << "\nChunkSize " << offsetof(WAV_HEADER, ChunkSize) << std::endl;
std::cout << "\nWAVE[4] " << offsetof(WAV_HEADER, WAVE) << std::endl;
std::cout << "\nfmt[4] " << offsetof(WAV_HEADER, fmt) << std::endl;
std::cout << "\nSubchunk1Size " << offsetof(WAV_HEADER, Subchunk1Size) << std::endl;
std::cout << "\nAudioFormat " << offsetof(WAV_HEADER, AudioFormat) << std::endl;
std::cout << "\nNumOfChan " << offsetof(WAV_HEADER, NumOfChan) << std::endl;
std::cout << "\nSamplesPerSec " << offsetof(WAV_HEADER, SamplesPerSec) << std::endl;
std::cout << "\nbytesPerSec " << offsetof(WAV_HEADER, bytesPerSec) << std::endl;
std::cout << "\nblockAlign " << offsetof(WAV_HEADER, blockAlign) << std::endl;
std::cout << "\nbitsPerSample " << offsetof(WAV_HEADER, bitsPerSample) << std::endl;
std::cout << "\nwExtSize (2) " << offsetof(WAV_HEADER, wExtSize) << std::endl;
std::cout << "\nFact[4] " << offsetof(WAV_HEADER, Fact) << std::endl;
std::cout << "\nDwFactSize " << offsetof(WAV_HEADER, DwFactSize) << std::endl;
std::cout << "\ndwSamplesWritten " << offsetof(WAV_HEADER, dwSamplesWritten) << std::endl;
std::cout << "\nData[4] " << offsetof(WAV_HEADER, Data) << std::endl;
std::cout << "\ndwDataLength " << offsetof(WAV_HEADER, dwDataLength) << std::endl;
return 0;
}
int getFileSize(FILE *inFile)
{
int fileSize = 0;
fseek(inFile,0,SEEK_END);
fileSize=ftell(inFile);
fseek(inFile,0,SEEK_SET);
return fileSize;
}
To generate such a 32 Bit Float, 88200 Wav-file: sox input16_44100.wav -b 32 -e float output32F_88200.wav rate -s -a -v -L 88200
shortandlong? Might be better to use fixed-width integers – user4581301