[linux-audio-dev] mux concept paper

mimo mimo at restoel.net
Thu Feb 17 11:43:44 UTC 2005

Hi James,

James McDermott wrote:
> hi mimo,
> are you thinking of something like buzz (or maybe max/msp) where audio
> can be routed in a free-form network from sources (generators) to sink
> (master output)? i'm a big fan of this idea.

You got me! I am a long term buzz user, used it for live gigs, and wrote 
a keyboard based mixer for it. I have seen other people using max/msp -- 
impressive. But there are also some downsides which I want to overcome. 
The principal idea and the simplicity of buzz I think are unique.

>>the Preprocessor Level that lazily generates a set optimised list of instructions for the audio io level
> can you go into more detail on this point?

The idea goes like this. Usually what you do in this type of programme 
is build some sort of tree representation of the generators and effects. 
So you need some sort of algorithm to find the processing order of the 
different machines.
Most of the actual running time the processing order doesnt change. Only 
if the user adds or removes connections between machines the processing 
order has to be recalculated. Changes like the volume level between two 
machines or a control input into a machine (like sending a different 
note) do not have any impact on the processing order.
A lot of time is spent on finding the processing order. But this only 
needs to be done once in a while. The rest of the time it needs to run 
just a list of simple instructions, like mix buffer a and b to buffer c, 
run a machine on buffer c, etc.
'Lazily' means that the recalculation should be done 'in the 
background', while the output still comes from the 'old' processing 
order. Only when the new processing order is finished will it activated.
> are you planning to use ladspa/dssi plugins as the machines?

Ladspa is limited. I'd rather use a super class of Ladspa that allows 
using Ladspa, etc.

> i think it's a good idea to make something that can be relied on in a live gig.


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