[sdiy] MIDI Clock sync advice

Mikko Helin maohelin at gmail.com
Mon Mar 11 09:50:55 CET 2024


For each incoming MIDI clock calculate the 96-PPQN sync time (duration) -
divide the time difference by four, lets call it time96, and generate three
additional timer events which are time96 apart from each other. Increment
the global sequencer current time in that MIDI handler and the timer
(interrupt) handlers.


On Mon, Mar 11, 2024 at 7:01 AM Adam (synthDIY) <synthdiy at adambaby.com>
wrote:

>
>
> On 11 Mar 2024, at 11:39 am, Peter Pearson via Synth-diy <
> synth-diy at synth-diy.org> wrote:
>
> Wouldn't it just be easier to find an Atari ST and call it a day?
>
>
> Ha ha!
>
> or...
>
> just keep your sync info well away from everything else!
>
> e. g.  Before I started using Innerclock stuff, I sent "Tape Sync" or FSK
> to my Roland gear ( MC-50, R-8, MSQ-700, TR-909 and TR-707 all had the
> option) on a mono audio channel from the DAW.
> Worked well.
>
> A
>
>
> Innerclock Systems <https://www.innerclocksystems.com/>
> innerclocksystems.com <https://www.innerclocksystems.com/>
> [image: Main+Web+SS+Logo+A+Double+Cutout+Filter.jpeg]
> <https://www.innerclocksystems.com/> <https://www.innerclocksystems.com/>
>
>
>
>
>
>
>
>
>
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>
>
> On Sun, Mar 10, 2024 at 9:27 PM brianw <brianw at audiobanshee.com> wrote:
>
>> One thing I forgot to mention is that time stamps allow transport jitter
>> to be corrected. So long as the time stamps themselves are not subject to
>> jitter, and the largest jitter delay is known, then the sequencer can force
>> a fixed latency between input and output. The accurate time stamps (if
>> available) can be used to schedule output MIDI at a fixed latency / delay.
>> That latency could be 5 ms, 10 ms, or maybe as high as 12 ms (depending
>> upon other latency in the signal path), but the musicians will
>> automatically adapt to reasonable latency after the jitter is corrected /
>> removed.
>>
>> This is where technology like CoreMIDI and MOTU's MTP are beneficial.
>> They're not available everywhere, though.
>>
>> Brian
>>
>>
>> On Mar 10, 2024, at 6:19 PM, brian wrote:
>> > On Mar 10, 2024, at 6:08 AM, Mike Bryant wrote:
>> >> High speed USB is 125uS, but in general the cheaper MCUs used in most
>> musical instruments still work on lower speed.  But in any case it's still
>> prone to an element of jitter which may or may not be a problem.  I'd love
>> to find a real drummer accurate to 1mS :-)
>> >
>> > Accurate and precise are two different aspects of timing measurement.
>> You can't just dismiss one or the other arbitrarily. That's true for all
>> scientific measurements.
>> >
>> > When it comes to music, we also have the human ability to correct for
>> latency, but not for jitter. So, an accurate drummer might be ahead or
>> behind the other musicians, based on where their kit is set up on stage,
>> but that timing error is constant if the drummer has a good "feel" - the
>> other musicians all subconsciously adapt to the latency.
>> >
>> > Acceptable latency is 10 ms to 12 ms in the studio. A band playing
>> together on a stage experiences delays of 5 ms to 10 ms due to the speed of
>> sound. But the feel of a drum beat requires timing down to some smaller
>> level to preserve the feel. If the snare is 5 ms behind, it sounds in the
>> 'groove.' 7 ms ahead and it has 'snap.' But if the hits are moving around
>> by a significant fraction of that, due to jitter, the 'feel' will not be
>> consistent. In an October 1987 article from Electronic Musician, Craig
>> Anderton quotes Larry Fast as saying that controlling the sound with
>> precision under a millisecond makes synthetic drum patterns sound more
>> realistic (human).
>> >
>> > That's not an exact figure - less than a millisecond - but it says to
>> me that we should probably aim for an order of magnitude better than what
>> people can hear, just to preserve the feel.
>>
>>
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