[linux-audio-user] Re: Linux Lighting

[Dirk Jagdmann]

> That's an important point. But if I understand correctly, I need to know how to
> "merge" or "route" DMX streams, either at software or hardware level. Needs some
> investigation...

When merging DMX data it only makes sense to choose the highest value 
from two (or more) channels for the output value. In lighting speak this 
is named HTP "highest takes place/precedence".
Routing of your DMX stream would be up to your software, but for your 
setup would be easy. You would have one of the following setups:

YourComputer ---> LightingConsole ---> DMX equipment

In this case there's nothing for you todo, as the lighting console will 
merge the DMX data coming from you. If the console does not have this 
capability you would have to change this to:

LightingConsole ---> YourComputer ---> DMX equipment

So you'd need an DMX input interface, read it and merge it with your DMX 
data.

> <newProject>
> * Name : Jacklight
> * Purpose : act as a bridge between Jack audio streams and DMX lighting
> * Basic features :
>     1 - set the brightness of a lamp according to the level of a given audio
>         stream
>     2 - a single stream can be connected to several DMX channels (= several
>         lamps), and several streams can be connected to a single DMX channel.
>     3 - each DMX channel is assigned a level control, to customize the
>         audio-to-brightness conversion ratio

Makes sense, and I think it should be doable by a weekend of hacking 
some code together.

> * Advanced features :
>     4 - GUI : a gtk based interface that allows to easily add/remove DMX
>         channels. Additionally, it could try and represents lamps on the screen,
>         with some (customizable) color squares

GUI is always nice, but this often takes much time when implementing, 
because
1) a good GUI is not easy to design and implement
2) if you have a good GUI you often have much "expressive" capabilities 
which then take some code to use.

>     5 - Midi : each channel level control could be assigned to a Midi
>         Continuous Controller. For Live operation, that would allow to use a
>         hardware controller, and turn a knob to decrease/increase every
>         channels' audio-to-brightness ratio,

Depending on how sophisticated you want a midi<->dmx mapping this can be 
really easy by noticing that: midi value range 0-127, dmx value range 
0-255. So you can make a 1to1 mapping by multipling/dividing all values 
by 2. Of course advanced features need more time to implement and it 
quickly becomes complex.

I personally have not used JackBeat yet, so I can't comment on specific 
issues with that software. My comments are just my general experience 
with lighting software gained from 3 attempts by Michael and me to write 
a medium sized lighting software (which all more or less failed, because 
if you want to have something better than real basic [as my dmxconsole 
ncurses program] it quickly becomes a *real* program, which takes a lot 
of developers ressources.)

In the dmx4linux archive Michael has coded an xmms plugin which assign 
each of the (fake) xmms spectrum bars to one DMX channel. If you want to 
have a quick check if your light setup works by some not random blinking 
it's a nice tool, however not usable for any serious lighting work.

-- 
---> Dirk Jagdmann ^ doj / cubic
----> http://cubic.org/~doj
-----> http://llg.cubic.org