typedef struct {
    WAVEFORMATEX    Format;
    union {
        WORD wValidBitsPerSample;       
        WORD wSamplesPerBlock;          
        WORD wReserved;                 
    } Samples;
    DWORD           dwChannelMask;      
                                        
    GUID            SubFormat;
} WAVEFORMATEXTENSIBLE, *PWAVEFORMATEXTENSIBLE;