RT MIDI

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Drumfix
Established Member
Posts: 185
Joined: Mon Jan 26, 2009 5:15 pm

Re: RT MIDI

Postby Drumfix » Fri Dec 07, 2018 7:23 am

If using a USB audio/midi device make sure that the ksoftirqd process on the core where the USB host controller irq is running is also running at realtime priority. And move away all other irqs from this core.

merlyn
Established Member
Posts: 50
Joined: Thu Oct 11, 2018 4:13 pm

Re: RT MIDI

Postby merlyn » Mon Dec 10, 2018 8:44 pm

raboof wrote: Looks like the MPU-401 had a Pulses-Per-Quarter-Note (PPQN) of 24


24 seemed like a strange number until I realised the significance of 24 = 2 * 3 * 4

1 tick = 64th note triplet
2 ticks = 32nd note triplet
3 ticks = 32nd note
4 ticks = 16th note triplet
6 ticks = 16th note
8 ticks = 8th note triplet
12 ticks = 8th note

That means this old standard had a musical time base, in contrast with a modern system that uses the sample rate as the time base.

merlyn
Established Member
Posts: 50
Joined: Thu Oct 11, 2018 4:13 pm

Re: RT MIDI

Postby merlyn » Wed Dec 12, 2018 1:54 am

I found this on the Ardour blog :

Paul Davis wrote:There is a lot of work to do on Ardour's MIDI workflow. But before that can happen, there are several subtle errors that are caused by the way released versions of Ardour have handled musical time. When you edit and move a MIDI note forward by a quarter note, that process would actually involve several conversions back and forth between time measured in samples and time measured in musical units, and the result is (often) small errors accumulating that lead to the note beginning and end being "wrong".


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