I am writing an application that uses the mixer API. I intercept the MM_MIXM_CONTROL_CHANGE message to know when the a mixer control has been changed.
I'm particularly interested in the Line-In control, but all of them should be the same. Looking at the volume applet there is the "volume" slider which controls the level at which the signal enters the mixer. There is the "mute" button that stops the signal from reaching the speakers, but the signal can still be recorded unto a wave file.
So far so good, I can easily check when either of these controls changes state.
If you go to Options->Properties you can select the Recording controls. Here there is the slider again, which is exactly the same slider as in the Playback controls. There is also a "select" button. As far as I can tell "select" completely blocks the signal from comming into the system at all. You can't hear or record it.
This is where my problem is. I can't figure out how to tell when the select button is pressed. There doesn't seem to be a control associated with it in the mixer API. Changing it does send two MM_MIXM_CONTROL_CHANGE message, the lParam (which indicates the control) is first 0, then 1. Funny thing is that ALL the select buttons send the same exact lParam's even though they are clearly different in functionality.
Is there any way to tell when these buttons are toggled?