Re: Enable system volume when driver doesn't
Re: Enable system volume when driver doesn't
- Subject: Re: Enable system volume when driver doesn't
- From: "Mikael Hakman" <email@hidden>
- Date: Wed, 12 Mar 2008 13:13:03 +0100
- Organization: Datakonsulten AB
On March 12, 2008 1:20 AM, John Pitcairn wrote:
At 12:58 AM +0100 12/3/08, Mikael Hakman wrote:
Furthermore, the high end devices we are talking about are currently the
only means to get out low-jitter, multichannel, digital audio out from the
computer. I'm surprised that these vendors don't even try to broad their
market by such a simple thing as implementing OS X master volume control.
The RME devices do allow their internal hardware mixer's software
interface (TotalMix) to be controlled by standard MIDI CCs or standard
Mackie Control MIDI protocol. The MIDI ports used can be CoreMIDI virtual
ports that your app creates and uses to send/receive the appropriate
messages.
It's a great shame that manufacturers don't appear to be interested in
implementing the CoreAudio playthrough protocols that would allow host
apps to implement direct control of hardware multichannel routing/volume,
ie the equivalent of "ASIO direct monitoring". Then again, pretty much no
major host apps implement it either (?), so manufacturers don't see it as
being worth any effort. Chicken & egg.
Many thanks for the response John. Yes, RME devices appear to be developed
primarily as computer interfaces even if information on their site states
that it is possible to use them as standalone DA/AD converters. My current
project requires both - mix the digital output from the computer with
ongoing analogue streams from other devices and send all this to digital
outputs. Continue the A/D process even if computer is off. The other 2
devices I mentioned earlier appear to be standalone DA/AD converters
retrofitted with an FW interface. RME Fireface looks very promising and has
a number of features/functions not available on the others. Fully-fledged
hardware mixer and patch board functionality controlled by software
(TotalMix) being one of those. Ability to send, in real-time, all bits from
AES/SPDIF stream including control and auxiliary information (the 8 extra
bits from each 32 bits wide wire word) to an application being another. OTH,
the 2 other devices give me 8 channels of digital AES in/out directly
whereas RME requires a Lighpipe/AES converter box.
Being able to control the device by MIDI CCs is very useful but in my
current project I need OS X master volume control, and then only for the
outgoing from the computer channels. This is because OS X master volume
control reacts to remote IR commands. Use of such a remote IR control is
non-negotiable requirement in my current project. I was thinking about
taking care of IR events myself (we have already such an application) and
then controlling the volume by MIDI CCs or any API provided by device
vendor. This doesn't work because some of the standard/third party
applications use the 2 IR commands (arrow up/down or +/-) for a number of
functions, controlling the volume (by some API calls to OS X, I suppose)
only in a certain context. Therefore I need functional OS X master volume
control.
In addition I have to assure that the outgoing from the computer streams
never ever get out without attenuation (i.e. at FS), whatever user does or
doesn't, except of course intentionally increasing the volume to FS. So it
doesn't look better than I have to implement those 27 functions in a new
audio driver repeating most of them directly to the real driver. I wish I
hadn't.
/Mikael
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