Re: 'Ganged' or 'Linked' Hardware
Re: 'Ganged' or 'Linked' Hardware
- Subject: Re: 'Ganged' or 'Linked' Hardware
- From: Herbie Robinson <email@hidden>
- Date: Thu, 17 Apr 2003 15:57:39 -0400
At 11:41 PM -0400 4/16/03, B.J. Buchalter wrote:
Hi Andrew,
A couple of people have asked me about the lack of drivers that support
treating two (or more) identical hardware units as a single entity. ASIO
has such a feature and I know that both M-Audio and Metric Halo both
supported this in their ASIO OS 9 drivers but haven't done so yet in
their OS X drivers.
Does anyone know if ths is this a 'waiting for something to change in
CoreAudio' problem or a 'haven't got around to it yet - it's difficult'
problem or something else entirely ?
Its more of a 'haven't got around to it yet - it's difficult' due to the
nature of kext drivers coupled with the fact that it is possible for the
applications to do this in Userland (even across multiple unlike devices).
DP4 has this support (I have not tested it yet). We have done this in the
record panel code we have. I really expected Logic to do this, since they
could do it in OS 9 (e.g. Run ASIO and Mac A/V at the same time -- multiple
CA devices should have been more of the same). Anyway doing it in the kext
gives a partial solution (for a class of devices) but does not solve the
general case of disparate devices. Doing it in the kext has a number of
complications, because it is not clear that the user automatically wants to
consolidate every attached device, and communicating complex preferences to
the kext is a difficult process.
So, while (at least) we will be addressing this, there is still a benefit to
App vendors (or Apple) supporting access to multiple devices simultaneously.
There are two potential ways to do this:
1. Queue all the data from the HAL driver callbacks into FIFOs and
run another real time thread for DSP.
2. Run the DSP in one of the HAL callbacks and have the remaining
callbacks queue the data.
Either way is going to increase latency.
Any opinions as to which method is preferred?
Are there any recommendations from Apple?
--
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http://www.curbside-recording.com/ **
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