I have a problem (and have been having it for some time now) — the new sound mixer stack in Vista features new cool things, but also re-invents the wheel. Many applications that used to use Volume Mixer on a Windows system to mix different voiced outputs into one input (for example Wave-out + Line-in –> Stereo Mix) have since stopped working. The prime example of this behavior is the Shoutcast DSP plugin (could be useful for solution testing).
How Can I re-enable XP-mixer controls, or maybe emulate this behavior somehow, so that the program (SC DSP) can properly manage Microphone/Line-In playback volume along with Wave-out playback volume?
My thinking would be to emulate a program hooked-in into the Vista Mixer for Wave-Out and Line-out (or Mic speaker volume — all playback, shown as separate adjustable "programs" so that the Vista Mixer could refer to it) and 'hook' it into the system under some emulation representing itself as the old volume mixer control interface for the program, but I frankly have no idea how to do that.
To clarify: this is not my PC (it is a HP Pavilion laptop). The problem seems to exist mostly due to the fact that Vista mixer controls separate programs, not separate inputs/outputs. The hardware is fully capable of doing what is needed when using Windows XP. I am well aware of the fact that this is a driver issue, but the driver is simply prepared for what Vista presents to the programmer through interfaces. The mixer device – as seen in the operating system, however it might look in software – is based on the mixer APIs for Windows Audio control.
Search using Google on Vista and line-in playback volume control for more info on the problem (and the sheer amount of users affected by it). Of course, a re-write of the Shoutcast Source DSP plug-in for WinAMP would do the trick, but that is not likely to happen…
Best Answer
Controlling the volume levels of a soundcards indivudual input/output levels in Windows Vista mixer is possible using the audio EndPoint API
This should allow you to adjust the main volume, and the volume of and connected audio inputs. One wrinkle about this that when you enumerate the end points, if there isn't a microphone plugged into your soundcard, then nothing will be enumerated. This means you'll need to change your application to respond to "microphone plugged in" events, and notify the user appropriately.
Another option is to dip below the Microsoft Core Audio and access the WaveRT driver directly. This is a lot more work than using the WASAPI/Endpoint APIs, but will give you the most control over access to the inputs/outputs of the soundcard.