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

From: Brad Stewart
Subject: Re: [fluid-dev] Akai EWI-USB, Raspberry-Pi, and FluidSynth
Date: Mon, 16 Nov 2015 11:53:10 -0800
User-agent: Mozilla/5.0 (X11; Linux i686; rv:38.0) Gecko/20100101 Thunderbird/38.3.0

If you are using a EWI 4000, you can trigger the EWI's audio output on an oscilloscope on one channel, then attach the other channel to your PC audio output. It should then be very easy to see the latency.

On 11/14/2015 12:19 PM, Ben Gonzales wrote:
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 n 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?


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
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.

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