[Fluxus] max-synths

[David Griffiths]

Hi Kassen,

On 05/31/2012 09:46 PM, Kassen wrote:
> Dear dave,
> 
> I find max-synths in Fluxa a bit suspicious. In particular I was
> happily jamming along when adding a extra mooglp caused some highhat
> accents to be lost. No problem, I thought, I'll just increase
> max-synths. That did not help, not even for a generous increase. I
> then read the docs which talk about "synth graphs", which I take to
> refer to the node pulled by "play" and any children it may have
> -recursively- as one such "graph".

max-synths is really the maximum number of playing sounds at any one
time (whether they consist of 1 or 100 nodes, no difference). This is
mainly a "blunt instrument" to control CPU usage.

> I always assumed we cycle based on the number of nodes, not on the
> number of such graphs. That idea is strengthened by how adding a extra
> filter node to graph A would affect graph B. However, it does not
> explain how max-synths for generous amounts or for a value of 1 (to
> test) wouldn't affect what I hear.

When you lose parts of playing synth graphs which affects the sound,
it's because there are a fixed number of them and they are getting
recycled to use for new graphs. The number of nodes limit is about
memory use, and partly puts a ceiling on graph complexity for CPU.

There is almost certainly something funny going on though. I haven't for
example been able to work out the limiting factor between these key values:

* The max-synths value

* Total number of nodes: controlled by the constructor of m_Graph in
Fluxa.cpp (currently 70 of each type and 2000 terminal nodes)

* The EVENT_BUFFER_SIZE=256 set in Fluxa.h - this is the ring buffer
size for the commands sent to the synth, it's possible this is filling
up under extreme cases.

> Do we have any known issues there or am I simply using stuff in the
> wrong way? I'm happy to cheerfully go in with my surgical chain-saw
> but this sounds like something you might have notes on.

I would suggest chain-sawing the above variables and posting your results!

cheers,

dave