[wdmaudiodev] Creating more then 32 in & out devices for a virtual audio driver.....
- From: "Eshanye K.P" <eshanyekp@xxxxxxxxx>
- To: wdmaudiodev@xxxxxxxxxxxxx
- Date: Fri, 31 Dec 2004 07:49:33 -0800 (PST)
Hi all,
I have written a virtual audio driver based on the
framework MSVAD (Microsoft Virtual Audio Device), a
sample in recent releases of the DDK. This is written
for windows XP. I have done the .inf file in such a
way that whe i install the driver, i can see 32 in and
32 out devices in "Control Panel->sounds and audio
devices->sound playback and sound recording". The
number 32 is used because the the microsoft MNDN or
DDK help quates that windows XP (and above O/S's) do
not support more than 32 devices for each of the audio
APIs such as WaveIn and WaveOut. If i need to support
more than 32 devices for each of the virtual audio
card then what do i do ?
I have pasted the lines quoted by DDK regarding this..
I did not understand thr paragraph which says
"The limitation on the number of device interfaces
does not limit the number of devices. A subsystem
driver that manages several devices (four MIDI
devices, for instance) still requires only a single
device interface."
Does the above paragraph indicates that there can be
32 interfaces but each interface can have devices
without limits ? Then the list shown in "control
panel->sounds and audio devices" are interfaces or
devices ? what is the API call used to add several
devices to one interface ? Actually i want to map one
IN device to an OUT device so that i can do a virtual
bridge... this configuration i should be able to make
from "control panel->sounds and audio devices" and i
want to support more than 32 in and out devices.. how
can i do it ?
------pasted from DDK Help - begin--------------------
Windows 2000 Device-Interface Limits
[This is preliminary documentation and subject to
change.]
In Windows 2000, the Windows multimedia functions
allow a maximum of 10 device interfaces on each of the
following APIs: waveIn, waveOut, midiIn, midiOut,
mixer, and aux.
For example, an application can create up to 10 device
interfaces for waveIn devices, and another 10 for
waveOut devices.
In Microsoft® Windows® XP, the limit on the number of
device interfaces per API is increased from 10 to 32.
These limits do not apply to Windows 98/Me, which
allow
applications to create arbitrary numbers of device
interfaces.
A device interface uniquely identifies each subsystem
driver. For example, a device that ships with two
subsystem drivers-one for Sound Blaster and one for
USB-requires two device interfaces.
The limitation on the number of device interfaces does
not limit the number of devices. A subsystem driver
that manages several devices (four MIDI devices, for
instance) still requires only a single device
interface.
Example
For example, an adapter driver might expose the
following device interfaces:
Device interface 1: wave
Device interface 2: UART
Device interface 3: wavetable
Assume that these three device interfaces expose the
following devices:
> Device interface 1 (wave)
1 waveOut device
1 waveIn device
1 midiOut device (software synthesizer)
1 mixer device
1 aux device
> Device interface 2 (UART)
1 midiOut device (MPU401)
1 midiIn device (MPU401)
(0 for all other device types)
> Device interface 3 (wavetable)
1 midiOut device (wavetable synthesizer)
(0 for all other device types)
The following table summarizes the number of device
interfaces per device type:
Device type Number of device interfaces
waveOut 1
waveIn 1
midiOut 3
midiIn 1
mixer 1
aux 1
If a Windows 2000 system contains four of these
adapters, the total number of midiOut device
interfaces is 4x3 = 12. Windows installs only 10 of
the 12 midiOut device interfaces for use by its
multimedia functions. If an application calls
midiOutGetNumDevs, the call returns 10 rather than 12.
----------------------------End------------------------
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