[wdmaudiodev] Re: Solution for MSVAD loopback interface

  • From: Kannan Ramanathan <kannan.ramanathan@xxxxxxxxx>
  • To: wdmaudiodev@xxxxxxxxxxxxx
  • Date: Wed, 15 Dec 2010 15:34:02 +0530

Looping back data at VAD level is indeed possible.

Justin, look in to the CSaveData class. An instance of this is created for
every new stream (I am assuming you are using a single stream / simple
version of VAD). This is split in to logical frames and are marked for
getting written to a file later, by a workitem. If you want to copy this
data, my suggestion would be to have one CSaveData (may be in the parent
class) and make CopyFrom/CopyTo use the RW pointers in to this bfr.

Couple of caveats:
1) for every new_stream, find a way to re-synch RW ptrs (you want to always
send the latest data -- stale data == weird behavior!)
2) Your capture EP property shd match render EP (i.e., you cannot have a 6ch
render EP and 2ch capture EP -- unless you decide to do the proper
padding/conversion internally).

All the best.

----- Kannan Ramanathan

On Wed, Dec 15, 2010 at 3:24 PM, Mike Kemp <mjk@xxxxxxxxxxxx> wrote:

> Hi. This might be irrelevant or wrong, but I recall reading that as part of
> digital rights management (DRM) enforcement Microsoft makes it impossible to
> access audio from an output e.g. to route it to an input, except in a
> suitably signed driver. I'd be interested to know if I'm wrong here. M
> ----- Original Message ----- From: Justin Holleb
> To: wdmaudiodev@xxxxxxxxxxxxx
> Sent: Wednesday, December 15, 2010 9:44 AM
> Subject: [wdmaudiodev] Solution for MSVAD loopback interface
> I am having trouble sending the data from the output pins into the input
> pins. I want to be able to capture system sounds using MSVAD as the capture
> source. I've tried using rtlcopymemory to send the buffer from copyto to
> copyfrom, but I just got silence. Has anyone implemented MSVAD in this
> fasion? What are the changes that need to be made?
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