[linux-audio-user] Re: Linux Lighting

Olivier Guilyardi ml at xung.org
Mon Nov 28 11:03:54 EST 2005

Hi Dirk,

Dirk Jagdmann wrote:
>> The idea would be to modify my application (Jackbeat) to control light in
>> addition to sound, using dmx4linux (see:
>> http://llg.cubic.org/dmx4linux) and a
>> supported DMX controller.
> Should be very easy, as it's essentially just an 8 bit value for each
> "lamp" you'd like to control which directly drives the lamps intensity.

Just read http://llg.cubic.org/dmx4linux/coding.html, and some stuff at

Say I plan lighting for a specific club : is it like each lamp, effect, motor
will be assigned a to given channel ? I'd then ask the club's technician : "what
channel is this lamp assigned to ?" (or he'd give me specification)

For example : 4 lamps, on channels 1,2,11 and 12

I would then have to configure my app to issue something similar to :

dmx_t buffer[4] = {0x80, 0xFF, 0x80, 0xFF};
fd = open (DMXdev(&argc, argv), O_WRONLY);
lseek (fd, 0, SEEK_SET);
write (fd, buffer, 2 * sizeof (dmx_t));
lseek (fd, 10 SEEK_SET);
write (fd, buffer, 2 * sizeof (dmx_t));

That would set two lamps to half brightness, and the other two lamps to full
brightness... Is this right ?

>> I just checked this 55 EUR Enttec USB controller :
>> http://www.enttec.com/opendmxusb.php
>> This firm seems to officially support Linux. Looks great...
> I would suggest this one. It's cheap, supported and plug'n'play.
> A Linux 2.6.x version of dmx4linux will be out in the next weeks.

All of this sounds great. But how stable is dmx4linux ? Already used it on real
live shows ? (I'm not talking about big/huge shows)

[The following is quoted from your previous answer in this thread]
> You should expect that lighting equipment should be DMX controlled today. So
> this technically solves to connecting your DMX controller (from laptop) to the
> DMX cable of the lighting console at the location. However be prepared that they
> might have more than 1 DMX universe/cable due to the local installation so to
> use all lights you'll need more than 1 universe on your DMX interface. Or two
> interfaces with 1 universe each. That's the reason why you should contact a
> local technican beforehand.

Got it. If DMX is a such common standard, I can safely be dependent on it. I'll
forget about the few DMX-unfriendly places I find. And if I really want to play
in some of these non-equiped place, I'll try and rent dimmers and lamps.

For a second universe, is it simply a matter of plugging a second Enttec device
and accessing channels 513-1024 ?

> If they don't own a DMX controlled lighting evironment I won't make myself any
> trouble trying to connect to "their" lighting equipment with my own dimmers,
> unless you're prepared to spent several days ripping their whole installation
> apart (which they probably would not allow anyway).

Okay, let's forget about that. All I need is a DMX controller and the club's
equipment spec.

Thanks a lot !


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