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(Created page with "Waveform Audio File Format, WAV was introduced by Microsoft and IBM. WAVE is RIFF's equivalent of AIFF, and its inclusion in Microsoft Windows 3.1 has made it important to know ...")
 
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Waveform Audio File Format, WAV was introduced by Microsoft and IBM.
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Waveform Audio File Format (WAV) was introduced by Microsoft and IBM.
   
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WAVE is RIFF's equivalent of AIFF, and its inclusion in Microsoft Windows 3.1 has made it important to know about.
 +
WAVE is RIFF's equivalent of AIFF, and its inclusion in Microsoft Windows 3.1 made it prominent.
   
  ⚫
The following is a simple description of a WAV file and will generally only work when it contains PCM data.
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Rob Ryan was kind enough to send me a description of the RIFF format. Unfortunately, it is too big to include here (27 k), but I've made it available for anonymous ftp at ftp://ftp.cwi.nl/pub/audio/RIFF-format.
  
   
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Conor Frederick Prischmann <conor@owlnet.rice.edu> points to ftp://ftp.ircam.fr/pub/music/.
  
   
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WAVe file format (Microsoft)
⚫
The following is a overly simple description of a WAV file and will generally only work when it contains PCM data. This isn't so bad since thats what 90% want to work with.
  
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⚫
WAVe file format (Microsoft)
  
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----------------------------
  
 
 
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Wave files are a part of a file interchange format, called
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Wave files are a part of a file interchange format, called
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RIFF, created by Microsoft. The format basically is composed
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RIFF, created by Microsoft. The format basically is composed
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of a collection of data chunks. Each chunk has a 32-bit Id
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of a collection of data chunks. Each chunk has a 32-bit Id
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field, followed by a 32-bit chunk length, followed by the
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field, followed by a 32-bit chunk length, followed by the
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chunk data. Note that values are in Intel form (ie: big-
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chunk data. Note that values are in Intel form (ie: big-
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endian notation).
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endian notation).
 
 
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The format for a wave file is as follows:
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The format for a wave file is as follows:
 
 
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Offset Description
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Offset Description
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------ -----------
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------------------
⚫
0x00 chunk id 'RIFF'
  
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⚫
0x04 chunk size (32-bits)
  
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0x08 wave chunk id 'WAVE'
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0x00 chunk id 'RIFF'
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0x0C format chunk id 'fmt '
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0x04 chunk size (32-bits)
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0x10 format chunk size (32-bits)
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0x08 wave chunk id 'WAVE'
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0x0C format chunk id 'fmt '
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0x14 format tag (currently pcm)
  
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0x10 format chunk size (32-bits)
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0x16 number of channels 1=mono, 2=stereo
  
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0x14 format tag (currently pcm)
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0x18 sample rate in hz
  
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0x16 number of channels 1=mono, 2=stereo
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0x1C average bytes per second
  
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0x18 sample rate in hz
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0x20 number of bytes per sample
  
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0x1C average bytes per second
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1 = 8-bit mono
  
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0x20 number of bytes per sample
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2 = 8-bit stereo or
  
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16-bit mono
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1 = 8-bit mono
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4 = 16-bit stereo
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2 = 8-bit stereo or
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16-bit mono
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0x22 number of bits in a sample
  
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4 = 16-bit stereo
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0x24 data chunk id 'data'
  
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0x22 number of bits in a sample
⚫
0x28 length of data chunk (32-bits)
  
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0x2C Sample data
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0x24 data chunk id 'data'
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0x28 length of data chunk (32-bits)
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0x2C Sample data
 
 
 
 
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Notes
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Notes
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-----
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-----
 
 
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1. Lengths do not include the chunk Id or the length bytes.
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1. Lengths do not include the chunk Id or the length bytes.
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e.g.: if the data length is 1204 then the length of
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e.g. if the data length is 1204 then the length of sample data is 1204 and not 1204-(4+4)
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sample data is 1204 and not 1204-(4+4)
  
 
 
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2. For samples with more than 1 channel, channel 0 data will
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2. For samples with more than 1 channel, channel 0 data will
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start and be followed by channel 1 for a given sample
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start and be followed by channel 1 for a given sample then the next sample will follow.
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then the next sample will follow.
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e.g. for 8-bit stereo the samples will sample0left,
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sample0right, sample1left, sample1right, etc.
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e.g.: for 8-bit stereo the samples will sample0left,
  
⚫
sample0right, sample1left, sample1right, etc.
  
 
 
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3. 8-bit samples are stored in excess-128 notation. This
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3. 8-bit samples are stored in excess-128 notation. This means that the value 0 is stored as 128, a value 1 is
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means that the value 0 is stored as 128, a value 1 is
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stored as 129, a value of -1 is stored as 127 and so on.
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4. 16-bit samples are stored as 2's compliment signed numbers.
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stored as 129, a value of -1 is stored as 127 and so on.
  
 
 
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4. 16-bit samples are stored as 2's compliment signed
  
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numbers.
  
 
 
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Sample C Structure
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------------------
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Sample C Structure
  
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------------------
  
 
 
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typedef unsigned word;
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typedef unsigned word;
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typedef unsigned long dword;
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typedef unsigned long dword;
 
 
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struct WAVEheader
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struct WAVEheader
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{
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{
  
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char ckID[4]; /* chunk id 'RIFF' */
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char ckID[4]; /* chunk id 'RIFF' */
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dword ckSize; /* chunk size */
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dword ckSize; /* chunk size */
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char wave_ckID[4]; /* wave chunk id 'WAVE' */
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char wave_ckID[4]; /* wave chunk id 'WAVE' */
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char fmt_ckID[4]; /* format chunk id 'fmt ' */
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char fmt_ckID[4]; /* format chunk id 'fmt ' */
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dword fmt_ckSize; /* format chunk size */
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dword fmt_ckSize; /* format chunk size */
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word formatTag; /* format tag currently pcm */
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word formatTag; /* format tag currently pcm */
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word nChannels; /* number of channels */
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word nChannels; /* number of channels */
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dword nSamplesPerSec; /* sample rate in hz */
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dword nSamplesPerSec; /* sample rate in hz */
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dword nAvgBytesPerSec; /* average bytes per second */
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dword nAvgBytesPerSec; /* average bytes per second */
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word nBlockAlign; /* number of bytes per sample */
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word nBlockAlign; /* number of bytes per sample */
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word nBitsPerSample; /* number of bits in a sample */
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word nBitsPerSample; /* number of bits in a sample */
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char data_ckID[4]; /* data chunk id 'data' */
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char data_ckID[4]; /* data chunk id 'data' */
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dword data_ckSize; /* length of data chunk */
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dword data_ckSize; /* length of data chunk */
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};
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};
  
  +
  +
  +
  +
Back to [[Sample File Formats (Audio)]]

Latest revision as of 20:50, 25 March 2016

Waveform Audio File Format (WAV) was introduced by Microsoft and IBM.

WAVE is RIFF's equivalent of AIFF, and its inclusion in Microsoft Windows 3.1 made it prominent.

The following is a simple description of a WAV file and will generally only work when it contains PCM data.


WAVe file format (Microsoft)

Wave files are a part of a file interchange format, called RIFF, created by Microsoft. The format basically is composed of a collection of data chunks. Each chunk has a 32-bit Id field, followed by a 32-bit chunk length, followed by the chunk data. Note that values are in Intel form (ie: big- endian notation).

The format for a wave file is as follows:


Offset Description

0x00 chunk id 'RIFF' 0x04 chunk size (32-bits) 0x08 wave chunk id 'WAVE' 0x0C format chunk id 'fmt ' 0x10 format chunk size (32-bits) 0x14 format tag (currently pcm) 0x16 number of channels 1=mono, 2=stereo 0x18 sample rate in hz 0x1C average bytes per second 0x20 number of bytes per sample 1 = 8-bit mono 2 = 8-bit stereo or 16-bit mono 4 = 16-bit stereo 0x22 number of bits in a sample 0x24 data chunk id 'data' 0x28 length of data chunk (32-bits) 0x2C Sample data


Notes

1. Lengths do not include the chunk Id or the length bytes. e.g. if the data length is 1204 then the length of sample data is 1204 and not 1204-(4+4)

2. For samples with more than 1 channel, channel 0 data will start and be followed by channel 1 for a given sample then the next sample will follow. e.g. for 8-bit stereo the samples will sample0left, sample0right, sample1left, sample1right, etc.

3. 8-bit samples are stored in excess-128 notation. This means that the value 0 is stored as 128, a value 1 is stored as 129, a value of -1 is stored as 127 and so on. 4. 16-bit samples are stored as 2's compliment signed numbers.


Sample C Structure

typedef unsigned word; typedef unsigned long dword;

struct WAVEheader { char ckID[4]; /* chunk id 'RIFF' */ dword ckSize; /* chunk size */ char wave_ckID[4]; /* wave chunk id 'WAVE' */ char fmt_ckID[4]; /* format chunk id 'fmt ' */ dword fmt_ckSize; /* format chunk size */ word formatTag; /* format tag currently pcm */ word nChannels; /* number of channels */ dword nSamplesPerSec; /* sample rate in hz */ dword nAvgBytesPerSec; /* average bytes per second */ word nBlockAlign; /* number of bytes per sample */ word nBitsPerSample; /* number of bits in a sample */ char data_ckID[4]; /* data chunk id 'data' */ dword data_ckSize; /* length of data chunk */ };


Back to Sample File Formats (Audio)

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