out.h

#define OUT_VER 0x10

typedef struct 
{
    int version;		// module version (OUT_VER)
    char *description;		// description of module, with version string
    int id;			// module id. each input module gets its own. non-nullsoft modules should
				// be >= 65536. 

    HWND hMainWindow;		// winamp's main window (filled in by winamp)
    HINSTANCE hDllInstance;	// DLL instance handle (filled in by winamp)

    void (*Config) (HWND hwndParent); // configuration dialog 
    void (*About) (HWND hwndParent);  // about dialog

    void (*Init)();		// called when loaded
    void (*Quit)();		// called when unloaded

    int (*Open) (int samplerate, int numchannels, int bitspersamp, int bufferlenms, int prebufferms);
		// returns >=0 on success, <0 on failure
		// NOTENOTENOTE: bufferlenms and prebufferms are ignored in most if not all output plug-ins. 
		//    ... so don't expect the max latency returned to be what you asked for.
		// returns max latency in ms (0 for diskwriters, etc)
		// bufferlenms and prebufferms must be in ms. 0 to use defaults. 
		// prebufferms must be <= bufferlenms

    void (*Close)();	// close the ol' output device.

    int (*Write) (char *buf, int len);	
		// 0 on success. Len == bytes to write (<= 8192 always). buf is straight audio data. 
		// 1 returns not able to write (yet). Non-blocking, always.

    int (*CanWrite) ();	// returns number of bytes possible to write at a given time. 
			// Never will decrease unless you call Write (or Close, heh)

    int (*IsPlaying)(); // non0 if output is still going or if data in buffers waiting to be
			// written (i.e. closing while IsPlaying() returns 1 would truncate the song

    int (*Pause)(int pause); // returns previous pause state

    void (*SetVolume) (int volume);	// volume is 0-255
    void (*SetPan) (int pan);		// pan is -128 to 128

    void (*Flush) (int t);		// flushes buffers and restarts output at time t (in ms) 
					// (used for seeking)

    int (*GetOutputTime)();		// returns played time in MS
    int (*GetWrittenTime)();		// returns time written in MS (used for synching up vis stuff)

} Out_Module;