WAVE Format Chunk

The WAVE format chunk <fmt-ck> specifies the format of the <wave-data>. The <fmt-ck> is defined as follows:

<fmt-ck>      fmt(      <common-fields>
                          <format-specific-fields> )
<common-fields> 
          struct
          {
            USHORT  usFormatTag;          /* Format category       */
            USHORT  usChannels;           /* Number of channels    */
            ULONG   ulSamplesPerSec;      /* Sampling rate         */
            ULONG   ulAvgBytesPerSec;     /* For buffer estimation */
            USHORT  usBlockAlign;         /* Data block size       */
          }

The fields in the <common-fields> chunk are as follows:

Field

Description
usFormatTag
A number indicating the WAVE format category of the file. The content of the <format-specific-fields> portion of the 'fmt' chunk, and the interpretation of the waveform data, depend on this value.

You must register any new WAVE format categories. See Registering Multimedia Formats for information on registering WAVE format categories.

WAVE Format Categories lists the currently defined WAVE format categories.

usChannels
The number of channels represented in the waveform data, such as 1 for mono or 2 for stereo.
ulSamplesPerSec
The sampling rate (in samples per second) at which each channel should be played.
ulAvgBytesPerSec
The average number of bytes per second at which the waveform data should be transferred. Playback software can estimate the buffer size using this value.
usBlockAlign
The block alignment (in bytes) of the waveform data. Playback software needs to process a multiple of usBlockAlign bytes of data at a time, so the value of usBlockAlign can be used for buffer alignment.

The <format-specific-fields> consist of zero or more bytes of parameters. Which parameters occur depends on the WAVE format category-see the following section for details. Playback software should be written to allow for (and ignore) any unknown <format-specific-fields> parameters that occur at the end of this field.

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