diff --git a/include/xaudio2.idl b/include/xaudio2.idl
index 277fc450469..b07c562914b 100644
--- a/include/xaudio2.idl
+++ b/include/xaudio2.idl
@@ -572,6 +572,18 @@ interface IXAudio2 : IUnknown
         [in, defaultvalue(NULL)] void* pReserved);
 }
 
+[
+    object,
+    local,
+    uuid(84ac29bb-d619-44d2-b197-e4acf7df3ed6)
+]
+interface IXAudio2Extension : IUnknown
+{
+    void GetProcessingQuantum(UINT32 *quantum_numerator, UINT32 *quantum_denominator);
+
+    void GetProcessor(XAUDIO2_PROCESSOR *processor);
+}
+
 const UINT32 XAUDIO2_DEBUG_ENGINE           = 0x00000001;
 const UINT32 XAUDIO2_VOICE_NOPITCH          = 0x00000002;
 const UINT32 XAUDIO2_VOICE_NOSRC            = 0x00000004;