[wdmaudiodev] Re: Audio: How should I make this?
- From: Tim Roberts <timr@xxxxxxxxx>
- To: wdmaudiodev@xxxxxxxxxxxxx
- Date: Mon, 15 Oct 2007 17:22:38 -0700
Juicehifi wrote:
>
> "Why would you choose to do it that way, instead of writing a filter
> driver (for XP) or an APO (for Vista)? Those would seem to be much
> less intrusive mechanisms, with much less reinventing of the wheel."
> I was hoping that this would be as simple as splitting one of the DDK
> audio driver examples, take the user mode interface from it, send the
> audio to buffers for processing and build a player on the back side
> for the downstream - and syncronize the two audiostreams by forwarding
> the callbacks upstream. Is this a very complicated task?
I, personally, would judge it to be much more complicated than the
filter driver and APO solutions. The big advantage of a filter driver
is that all of the boilerplate stuff is being done for you by the driver
you're leeching from. You intercept and modify only those requests that
interest you.
> The solution doesn't really have to be a driver, but it is important
> that the solution is connected to the choosen sound card in such a way
> that all audio sent to this particular sound card goes through the
> solution. Each time the machine is turned on and until the user
> chooses to disable the solution.
>
> Maybe it should be a filter driver and an APO. I don't know. Will a
> filter driver / APO solution work with Asio playback in addition to
> the windows audio API?
The filter driver certainly should. ASIO on XP talks to the kernel
streaming driver, so it should pick up any filter. On Vista, I don't
know. The ASIO web site says it now supports WaveRT drivers on Vista,
but I don't know whether that means it talks DIRECTLY to the WaveRT
drivers. If so, that would bypass any APOs.
Note, however, that I have zero personal experience with ASIO. It is
possible that I have waded out of my depth here and should just shut up.
> The solution should not be dependant on cooperation from the
> application. In fact, removing dependancies of the various audio
> sources is one of the main motivations for making a solution. It is
> also important that the solution is guaranteed to be in the audio
> rendering stream whenever audio is routed to the subject sound card.
> The solution should have a very straightforward installation procedure
> that is works as long as the player and sound card supports certain
> defined audio API's. And as long as decoded autio is played. This also
> means that it will have to sit further down the stream than a mp3 /
> AC3 or any other audio decoder would sit.
Yes, naturally. This also means that your driver will not be allowed to
participate in protected content on Vista.
> Some of todays users send the audio to an available audio output -
> then loops the audio back to audio inputs - then from the inputs to a
> VST/DX host for processing and finally to the outputs of the the sound
> card that's actually being used for the playback. This solution
> strikes me as unneccesary complicated.
Isn't that exactly the solution you are proposing, with the one
exception that you'll configure the playback path yourself?
> Is this a "mission impossible"?
It's not "mission impossible", but it's not a slam dunk, either.
--
Tim Roberts, timr@xxxxxxxxx
Providenza & Boekelheide, Inc.
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