Re: [iiwusynth-devel] Fw: Re: [linux-audio-dev] more about iiwusynth

[Josh Green]

On Mon, 2002-06-10 at 19:09, Peter Hanappe wrote:
> 
> Hi Juan,
> Hi all,
> 
> I was a LinuxTag this weekend showing Swami and the iiwusynth so I
> missed the whole discussion this weekend. I'll try to catch up a bit.
> 

Tell us how it went :) I'm curious about your experience with Swami in
particular.

> 
> So I repeat my point, yes, we should go for fixed point if that makes
> us gain CPU. But there is CPU to gain from managing the voice releases
> better as well.
> 

I wonder if an MMX and/or SSE core would give us significant gains? MMX
is INTEGER based parallel data processing, but I don't know much about
SSE. Also, it would seem like fixed point would also give us much more
efficient use of available sample range (all this has I think been
mentioned).

Should we start discussing ideas for better voice extinguishing? (Can
you tell I'm trying to get involved :)

Some thoughts (might be totally useless):

- It might be nice to have a configurable option for how voices are
selected for termination. The most useful value would seem to be
percentage of CPU time (although I have no idea how this could be
calculated) or perhaps, much easer max polyphony (a fixed number of
voices probably wont always equal the same amount of CPU time, right?).
Perhaps there could also be a soft and hard limit. Hitting the soft
limit would speed up the release stage, hard limit would just cut them
off (to allocate for new voices).

- Once this configurable threshold has been reached (CPU time or # of
voices) the current voices would be rated and the one with lowest
priority would be set for rapid release (the release time could perhaps
also be configurable?)
- Priority selection seems like where some smarts might be able to be
implemented, the rating ideally related to _perceptible_ volume level.
  Criteria (I seem to remember writing this before, can't remember if I
got any response though)
  - Volume envelope in release stage and its level (maybe take into
account the other stages of the volume envelope also, to see if it will
get any louder than it is currently is).
  - Attenuation (greater values = quieter)
  - Filter Cutoff and Filter Q (lower values of FilterFC and FilterQ =
quieter, since as FilterQ gets higher more of the FilterFC frequency can
be heard)

Perhaps a slightly silly question, but.. Does iiwusynth terminate
samples that are not looped and have reached the end of the sample (just
checking to see if perhaps the volume envelope is being heeded even when
no more sample).


Another question I have is what is taking up so much time when iiwusynth
is running IDLE (no voices ~ 19% of my P-II 366 CPU).

> 
> Cheers!
> Peter
> 
> 

I hope at least some of this is useful. Cheers.
        Josh Green