Re: IOAudioFamily : driver structure
Re: IOAudioFamily : driver structure
- Subject: Re: IOAudioFamily : driver structure
- From: nick <email@hidden>
- Date: Tue, 21 Sep 2004 09:38:59 +0100
Thanks a lot for the info, it's a BIG help!
I had started my driver as 2 separate AudioEngines, thankfully I
haven't spent too much time implementing that yet so I shouldn't lose
too much time :)
Shouldn't this information be in the "Writing Audio Device Drivers"
document? It seems pretty crucial to me! The document actually
encourages developers to use multiple AudioEngines..
Regards,
Nick
On 20 Sep 2004, at 22:24, Phil Montoya wrote:
The first rendition of our core audio driver achieved exactly the
results we intended and it worked as expected using Final Cut Pro.
Now that we had a "core audio" driver it was our assumption that other
apps who used core audio would work with our driver. To our dismay we
discovered this isn't necessarily so. We then took the extra step to
fix this so that our driver could be as compatible as possible with as
many applications as possible. To say we had an unusable driver is
inaccurate it actually worked very well with the application it was
written for. It just didn't work well with everything.
The moral of the story is that you can have a perfectly working core
audio driver that doesn't work with all core audio applications. And
if the assumption is a native full duplex engine then your hardware
better cooperate or this isn't possible.
-Phil
On Sep 20, 2004, at 12:13 PM, Jeff Moore wrote:
If you choose present your device as multiple engines, you should be
prepared for many apps not being able to use your other engines. For
some devices, this is fine and dandy and achieves what the device
developer is looking for. For other devices, like Phil's for
instance, it results in an unusable driver that doesn't come close to
achieving the desired results.
You, being the driver developer, need to figure out exactly what you
want to present to applications and then use the tools the IOAudio
Family provides to achieve that.
On Sep 20, 2004, at 10:26 AM, Phil Montoya wrote:
The single full duplex engine is more efficient and provides you
with a more compatible driver. However in order to use a single
engine it is critical that your hardware provide a single time stamp
for all of the streams (both input and output). There is just one
call to start and stop the engine and the timing is shared among all
streams.
Initially I created two engines one for input and the other for
output mainly because our hardware had separate wrap interrupts for
the input and output buffers. I discovered this driver worked in
most applications but there were some applications that assumed the
output device was full duplex and could also do input. Logic
Platinum 6 is one example, it never saw the input engine or input
stream.
I rewrote the driver to have a single engine and life is better.
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