[PlanetCCRMA] Ardour hardware monitoring

[R Parker]

Hi John,

I've had the same questions that you have and my
comments are all based on assumptions. Hopefully, I
won't add to much confusion. If I do, just put me on
ignore.

--- John Yates <jyates@hvc.rr.com> wrote:
> Anyone have hardware monitoring working with Ardour?
> My RME
> Digiface/Cardbus setup doesn't seen to be getting
> any mixer commands
> when hardware monitoring and Auto Input are enabled
> in Ardour.

I think there's recently been bug fixes to the Auto
Input.

 I've
> got hardware monitoring enabled in jackd also.

I don't own the hardware that you have. My
understanding of hardware monitoring is that the
signal level you send to the hardware input port is
routed to jack and its clients, and to the hardware
output port. The signal is split to the input stages
of two distinct interfaces; jack and the hardware
output.

 From
> what I gather,
> Ardour should be sending monitor switching commands
> to jackd which
> sends them on to the Alsa driver which sends them on
> as level changes
> to the HDSP hardware mixer.

I don't know why Ardour and jack both have switches
for Hardware Monitor and have assumed that they are
exactly the same feature. I've imagined that Ardour
gives you an interface to control monitoring options
via the hardware driver and so does jack. I'd also
like to know exactly what's happening.

Anyway, I suspect your understanding is correct until
you say "level changes". Ardour doesn't send fader
control instructions to a audio card hardware mixer.
With hard disk sources, the signal levels from Ardour
are exactly what hits the input of the hardware mixer.
With audio card input signals, live player punch in to
correct performance error,  the signal that returns to
your monitoring system while in Hardware monitoring
mode is symultaneously routed to Ardour and the output
ports of the audio card. So, the actual punch in that
you hear on record enabled Ardour tracks has never
been in Ardour. Consequently, you achieve zero latency
monitoring for the record enabled track.

 I can control the mixer
> with the
> hdspmixer utility so I know that much is working. Is
> there any
> preliminary mixer setup that must be done before
> Ardour can take
> control?

My assumption about these hardware mixers is that the
faders are synonymous with the input stage of a
hardware mixing consol. So, adjusting the fader level
would be the same as setting channel input gain/trim.

If this is accurate, and you don't have gain stages in
front of the hardware mixer then you would use that
interface to trim input signal levels. If you do have
gain stages in front of the audio card mixer, then
you'd leave the gain stages at 0.0dbfs.

> Monitor switching via software monitoring seems to
> work fine, but
> I'd rather get the hardware path going if I can.

If in hardware monitor mode, can you mute the Ardour
mixerstrip and still monitor the signal? That should
work, I assume. It stands to reason that you shouldn't
mute record enabled Ardour mixerstrips while in
hardware monitor mode. The mixerstrip output when
record enabled with hardware monitor turned on should
route hard disk sources until a rolling transport is
record armed. Then it should cease to route the
mixerstrip input source (signal from hard disk) but
continue routing the audio card input directly to the
audio card output.

I'm curious to find out just how whack my assumptions
about these interfaces is but hope not to confuse your
understanding of them.

Incidentally, if my thoughts are remotely accurate,
then that hardware mixer interface could be very
useful for signal routing. Assuming there are per
channel output gain stages and multiple D/A outputs,
you could  configure distinct monitor mixes. That
would very useful where you've got several studio
rooms; drum room (loud as hell click track), vocal
room (much less click track), guitar room (loop of
signal that infinitely repeats "turn it down":), etc.

John, I had coffee prior to writing this response. I
feel like I should have combined it with a
subscription amphetamine. I feel like I could rewrite
the above 20 times and still fail to produce an
articulate thought.

ron

> Thanks, John
> 
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>
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