RE: [iiwusynth-devel] Multi channel output and number of midi channels

[M. Nentwig]

Hei,

> I'm trying to make up for my abscence lately by writing very long
> mails. Hang on.

Don't worry, I'll be rather quiet next month (programming sounds and
preparing gigs, call it 'field-testing the synth).

What I don't understand about your approach with several aux buses is
how the output signal from the Fx is merged back into the multichannel
output. The two extremes would be one more matrix mixer (every Fx chain
to every output), or all Fx output only to L/R. Most older hardware
synths (take Korg 01RW or Alesis QS) do the latter - outputs 3 and 4 are
without Fx only.
A hardware mixer would have effect returns, which are routable to master
out and / or a subgroup.
Otherwise, as I said, I think it's a good idea, it's sufficiently
flexible for most uses, and it will work fine (just not for me).

If you want to allow loading arbitrary LADSPA plugins, you'll need
commands to load and unload them. You'll have to think about mono and
stereo inputs / outputs, about setting parameter values, and realtime
modulation of parameters.
All this is already done (the RT modulation is not yet implemented, but
the road is clear, see below).
In the end you'll end up with rewriting something very close to the
existing LADSPA 'subsystem'. I believe that the code I wrote is fully up
to the job, maybe I'm just selling it badly.
I wouldn't consider it a new 'language', it's more like a netlist format
(like in electrical engineering). It could be very easily extended to
multichannel inputs and multiple aux ways as you planned and
multichannel output while keeping the flexibility that I need. And there
are no unneeded gimmicks right now- it's just basic functionality.

> Let me know what you think about the ideas above. Can it suit you?
No, it won't be up to the job:

- Master effect: I use a tanh limiter in every sound I have programmed
as last plugin - it can tolerate some amount of clipping without
thrashing the sound.
- I would like to also add an equalizer just in front of it for every
sound, but haven't gotten around to it. It serves two purposes: First
for balancing the sound during programming, second for on-the-fly sound
manipulation without having to think much.
- Arbitrary control information: It is very easy to add a 'fake'
LADSPA-plugin, that reads the CC status of a given controller on a given
channel and puts it to its control output. Add parameters gain, offset,
lower limit and higher limit and 95 % of all reasonable effect real time
modulations are implemented!
- The current implementation allows as much freedom as possible (any
routing that doesn't have feedback loops). Why should we restrict
ourselves to a concept that is limited right from the start? Take for
example Propellerhead's 'Reason' (I know the demo): Arbitrary routing
capability.

>
> > My own RME Multiface has 10 analog output channels, so I
> can test the
> > multichannel synthesizer.
>
> Hey! You've got a RME multiface! Happy with it? No probs on Linux?

I haven't invested the amount of time that is appropriate, maybe one
working day, but the only applications that work are iiwusynth and
aplay.
I guess that the driver is OK, but the applications are not.
Jack doesn't work either, but it works with no other interface on my
machine. So that's not RME's fault.
The alsa driver with the latest patch works out of the box, but I have
to boot without card (otherwise SEGV when starting the driver). I
suspect the PCMCIA subsystem, others don't have that problem.
One reason for trouble is that it has a nonstandard sample format, so
'plughw' is needed. That's not a bug, but a feature, since the card has
more than 16 bits - soundblaster format cannot work.
With Iiwusynth it runs at the lowest possible latencies on an
off-the-shelf-kernel. There are infrequent dropouts now and then,
probably more buffers would help. Currently I don't care, they are
rather quiet.
The total latency (MIDI+audio) is so short, that I can't distinguish
between sounds coming from iiwusynth and the master keyboard, they just
happen at the same time. I'll measure it one day.
The PCMCIA card mechanics are not fully convincing. That said I'm quite
happy. Haven't tried full duplex, though.
I bought it at 'Amadeus Musicmedia'. Ordering took two weeks (it was not
on stock), but they had the lowest price.

Cheers

Markus