update comment

stepmania/src/arch/Sound/RageSoundDriver.h

@@ -34,9 +34,9 @@ public:
 	 * RageSound::CommitPlayingPosition. */
 	virtual int64_t GetPosition() const = 0;
 
-	/* When a sound is finished playing (GetPCM returns less than requested) and
-	 * the sound has been completely flushed (so GetPosition is no longer meaningful),
-	 * call RageSoundBase::SoundIsFinishedPlaying(). */
+	/* When a sound is finished playing (GetDataToPlay returns 0) and the sound has
+	 * been completely flushed (so GetPosition is no longer meaningful), call
+	 * RageSoundBase::SoundIsFinishedPlaying(). */
 
 	/* Optional, if needed:  */
 	virtual void Update() { }