4
1 Configuration
Operation on Windows Vista / 7 / 8 /
Server 2008 / 2008-R2 / 2012
The audio subsystem of Windows Vista / 7 / 8 has changed substantially
from earlier versions of Windows, although most applications should
continue to work without modification. The major differences likely to
affect users of the Digitorc 4 are described below.
Audio Endpoints
Key to the new system is the concept of audio endpoints. These are the
physical audio sources and destinations, such as microphones, speakers and
line connectors.
Previously, an audio capture device would typically have multiple inputs
which were combined in a mixer or selector. Under Windows Vista, each
input is represented by its own device, and Windows itself operates the
card’s selector to route the chosen source to the input stream.
In the case of the Digitorc 4, each of the physical line inputs is represented
by an endpoint device, and as the hardware has separate AES3 transceivers
for each one, they can be used simultaneously. There are also endpoint
devices for the digital loopback sources, although by default these are
disabled. To enable these sources, right-click on the loudspeaker symbol
at the bottom right-hand corner of the screen, select Recording Devices,
right-click anywhere in the window and select Show Disabled Devices.
Now right-click on the desired Wave Out Mix device and select Enable. This
source will now appear as one of the available audio recording devices.
Note that when an application is recording from a loopback endpoint, the
corresponding line input is unavailable, and vice versa.
Windows Vista has a default playback endpoint and a default recording
endpoint, which are typically used by applications where the input or
output device cannot be explicitly chosen. After the Digitorc 4 driver
is first installed, these may be randomly set to any of the outputs and
inputs. To set the default endpoints, right-click on the loudspeaker symbol,
select Playback Devices or Recording Devices, and then right-click on the
desired endpoint and select Set as Default Device. The default device is
remembered across reboots and should not need to be set again unless
additional audio hardware is installed, in which case the defaults may need
resetting.
Windows 7 and 8 provide separate defaults for communications
applications. When enabled, the Mono Mix inputs become the default
communications source.
Mixer API
By default, the mixer API under Windows Vista / 7 / 8 is virtualised for each
application, providing just a mute and volume control for each endpoint
and affecting only the audio going to and from that application. The
hardware controls on the card itself are not accessible from the mixer API in
this default mode.
For applications that need direct access to the hardware mixer controls,
or that need access to the line input monitor controls or peak meter
nodes, there are two options. Firstly, if it is a new application being
written specifically for Windows Vista / 7 / 8, it can be designed to use
the Core Audio APIs, which include the DeviceTopology API and the
EndpointVolume API (which includes the IAudioEndpointVolume and
IAudioMeterInformation interfaces). These are documented in the
Windows Vista SDK which is available from Microsoft, however note that
these APIs don’t work with earlier versions of Windows.
Alternatively, applications can be given access to the hardware mixer
controls through the mixer API by right-clicking on the application’s icon,
selecting Properties, clicking on the Compatibility tab and selecting Run this
program in compatibility mode for Windows XP Service Pack 2. Be aware,
though, that in this compatibility mode, the Digitorc 4 card is represented
by a single mixer device with destination lines for each of the individual