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Generating Four-Character Codes

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[The feature associated with this page, Multimedia File I/O, is a legacy feature. It has been superseded by Source Reader. Source Reader has been optimized for Windows 10 and Windows 11. Microsoft strongly recommends that new code use Source Reader instead of Multimedia File I/O, when possible. Microsoft suggests that existing code that uses the legacy APIs be rewritten to use the new APIs if possible.]

You can use the mmioFOURCC macro or the mmioStringToFOURCC function to generate four-character codes. The following example uses mmioFOURCC to generate a four-character code for "WAVE".

FOURCC fourccID; 
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. 
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fourccID = mmioFOURCC('W', 'A', 'V', 'E');

The following example uses mmioStringToFOURCC to generate a four-character code for "WAVE".

FOURCC fourccID; 
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. 
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fourccID = mmioStringToFOURCC("WAVE", 0);

The second parameter in mmioStringToFOURCC specifies flags for converting the string to a four-character code. If you specify the MMIO_TOUPPER flag, mmioStringToFOURCC converts all alphabetic characters in the string to uppercase. This is useful when you need to specify a four-character code to identify a custom I/O procedure because four-character codes identifying file-extension names must be all uppercase.