[sdiy] Smoothing MIDI data

[Tristan]

The Roland JX-3P and Oberheim Xpander have CV update rates of 100Hz which means 10mS between 
updates. The Kurzweil K2x00 synths have an internal modulation calculation rate of 50Hz which means 
interpolation between 20mS steps. 

I think these kind of rates are a compromise between avoiding clicks and pops and avoiding too much lag. 
For tight timing you could go down to the low mS but for smoother glides you might want to go up to 
100mS+

/Tristan

On Wed, Feb 28th, 2018 at 7:28 PM, Richie Burnett <rburnett at richieburnett.co.uk> wrote:

> Don't you mean 640us!?
> 
> -Richie, 
> 
> Sent from my Xperia SP on O2
> 
> ---- rsdio at audiobanshee.com wrote ----
> 
> >There are lots of options, depending upon your specifics.
> >
> >At one extreme, the fastest that a classic MIDI interface can update a CC
> value would be 640 nanoseconds. Even with 14-bit data, 99.2% of the updates
> can occur on 640 ns intervals thanks to the specification allowing for the
> LSB to be updated alone, with the MSB only updated as necessary.
> >
> >Based on that, I’d say your smoothing should have a time constant of at
> least 640 ns.
> >
> >Of course, the challenge is that MIDI data updates can also occur at much
> slower update rates, depending upon the implementation of the source. You
> might need an adaptive smoothing algorithm to minimize latency while still
> avoiding zipper noise.
> >
> >
> >Another option is analog smoothing. Eµ Systems released a paper via the AES
> that describes a Voltage-Controlled Lag Circuit. This allows each individual
> CV output to have independent, linear smoothing. I think this ended up in an
> Oberheim patent, US Patent # 3,969,682.
> >
> >Authors: Rossum, Dave; Wedge, Scott
> >Affiliation: Eµ Systems, Santa Clara, CA
> >AES Convention:57 (May 1977) Paper Number:1231 
> >Publication Date:May 1, 1977 
> >
> >
> >On Feb 27, 2018, at 8:56 AM, Bruno Afonso <bafonso at gmail.com> wrote:
> >> I've been developing a few MPE modules for VCVRack and I'm wondering what
> do people that develop firmware for hardware synths do when it comes to
> smoothing midi data, typically 7bit. I guess my question is a bit along the
> lines of how fast or slow do you move to the new mapped CV voltage. Are there
> good time constants that empirically work better?
> >
> >
> >_______________________________________________
> >Synth-diy mailing list
> >Synth-diy at synth-diy.org
> >http://synth-diy.org/mailman/listinfo/synth-diy
> 
> _______________________________________________
> Synth-diy mailing list
> Synth-diy at synth-diy.org
> http://synth-diy.org/mailman/listinfo/synth-diy
>