[wdmaudiodev] Re: help on MSVAD

  • From: Arijit Paul <arijitpaulin@xxxxxxxxx>
  • To: wdmaudiodev@xxxxxxxxxxxxx
  • Date: Mon, 30 Oct 2006 11:31:20 -0800 (PST)

Hi Hakon,

Thanks for replying to my query. We are not redirecting audio from one logical 
device to another. Allow me to explain the requirement more precisely - 
I am writing a virtual audio deriver which will be installed in windows. It 
will work as follows - a voice chat application will select this driver for 
audio i/p and o/p.
Think about this driver as your normal sound card driver. But instead of 
playing sound in your PC, it  will  make  all the voice data available to 
another application and this application will process this voice data in 
whatever way it wants. This way we can record the voice coming out from an 
application or play it in another PC. I have found one commercial s/w which 
already does something like this. The s/w is virtual audio cable
( http://nrcde.ru/music/software/eng/vac.html ) and this works perfectly fine 
in windows. My specific queries are:-

1) Can I modify MSVAD sample driver code and develop something which I require?
2) Since i am new to audio driver, can i expect some kick-start help from this 
group?
3) There are some bug in MSVAD due to which it writes small bogus audio files 
in my hard drive when i use that driver with an audio application. I heard this 
has been fixed. Can someone point me to that fix?

Thanks a lot.

-paul

----- Original Message ----
From: Hakon Strande <hakons@xxxxxxxxxxxxxxxxxxxxx>
To: wdmaudiodev@xxxxxxxxxxxxx
Sent: Tuesday, October 31, 2006 12:00:46 AM
Subject: [wdmaudiodev] Re: help on MSVAD

Dear Sir,

It is not recommended to build virtual drivers that covertly re-direct
audio streams from one logical device to another. 

In Windows Vista we are trying to create complete audio path
transparency for the benefit of Windows Vista users and applications and
enable discoverability of the actual audio peripherals that are being
used for the benefit of the user, the current and future versions of the
Windows OS media policy engine and to enable more powerful and flexible
Windows application experiences.

If you hide the true nature of where the audio stream is going you are
working against this initiative and while it may be technically possible
we can't help you do this, there is no Designed for Windows Logo for
such a driver and the audio system and audio device infrastructure may
change in ways that could break your virtual driver at any time with any
QFE or Service Pack.

In this case it is better to allow the user to select the device to be
used with the VOIP application using the application UI or allow the
application setup wizard to help the user through this selection
process. This way the application is aware of the device used, the user
can use many different logical devices with different applications for
different purposes (if needed) and furthermore it is absolutely
necessary for the application to know what device it is dealing with to
enable the right application graph processing algorithms based on the
nature of the logical device, such as for Mic Arrays for instance. 

Sincerely,

Hakon Strande
PM Integrated, Internal, External, and Wireless Audio Devices
MediaTech/DMD/Windows Client/Microsoft

-----Original Message-----
From: wdmaudiodev-bounce@xxxxxxxxxxxxx
[mailto:wdmaudiodev-bounce@xxxxxxxxxxxxx] On Behalf Of Arijit Paul
Sent: Saturday, October 28, 2006 11:28 PM
To: wdmaudiodev@xxxxxxxxxxxxx
Subject: [wdmaudiodev] help on MSVAD


Hi,



I have done lots of ground work, but could not find any satisfactory

explanation on this. My requirement is like that - i will have an 



pseudo audio driver registered. For one of my application (voice chat

application), I will select this driver for audio i/p and o/p.

Application will deliver any incoming voice to the pseudo driver for

audio o/p (in normal case, it would have been given to the sound card 



driver in the system). The pseudo audio driver will forward this voice

to somewhere else(lets say X). The pseudo audio driver will get user

voice i/p from X and forward it to the voice chat application (in that 

case X is acting as a microphone source).

Initially I was thinking it won't be possible in windows. Then I came

across MSVDM where they have written a driver for storing voice to a

file instead of o/p it to sound card. I was thinking to tweak this for 

my purpose.  Will it be possible to make this work for our requirement? 


Also, I heard a lot about kernel streaming. Do I need to devlop any
expertise on that too.

It will be helpful  if you can tell me  what  are the  things I need to

know  to develop this driver.  I have never  worked on audio  driver in

windows. Also, I heard there are some bugs in MSVAD which have been
fixed. Do you have any pointers on that?

An early reply will be very much appreciated.


Any pointers or help in this regard will be highly appreciated.



-paul






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