Re: [fluid-dev] Akai EWI-USB, Raspberry-Pi, and FluidSynth

[Ben Gonzales]

Hi all.

How do you measure latency with a wind controller? I decided to try the 
"record the actual sound and analyse" approach.

I tried using a mic next to the mouthpiece to record my "pfft" (leaking 
out the side), and the synth-ed sound that followed. It was difficult to 
distinguish the sounds. I then tried tapping with my free hand on the 
recording PC's mic in sync with my "pfft", i.e. trying to tap and blow 
at precisely the same time. After a bit of practice I measured about 
80ms delay.

Then I got a real recorder and a clarinet and did the same "tap and 
blow". I got about 40ms for that.

I know it's not very scientific, but I concluded that the traditional 
instruments have a delay before the sound is produced (maybe 40ms), and 
my synth increases that delay by about another 40ms.

When I play the EWI, however, I can't say that I notice a delay. Maybe 
it is because my brain is used to the inherent delay in the traditional 
instruments???

So, some questions:

1. How does one measure latency for a wind controller?
2. Does anyone have a HOWTO for a low latency implementation on a R-Pi?

Ben

On 01/11/15 10:52, Peter Billam wrote:
...
> I'm using a preempt-rt enabled kernel with hand-optimized IRQ
> priorities and that gives me a latency (from key press to start
> of sound) of about 12-15ms, which is acceptable.
> On an ARM: yay! well done. At
>    http://www.pjb.com.au/midi/osdc/index.html#03
> I reckon
>    About 10 milliseconds latency is acceptable.  Of the linux synths,
>    TiMidity doesn't meet this; fluidsynth maybe just meets it,
>    on a fast CPU.