Re: [LAD] making sense of Jack MIDI; or, is this an appropriate use for Jack?

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To: <linux-audio-dev@...>
Date: Sunday, February 17, 2013 - 2:28 am

On Saturday 16 February 2013 03:58:10 Frank Kober wrote:

A few people have mentioned tempo changes on the fly as a troublesome area.

So let me think about this:
Changing a tempo doesn't change the number of ticks. It does change the time
value (in nanoseconds) of each tick. So suppose at time x a tempo change
occurs. We let startTick = nanosToTicks(x) be our new starting tick for future
calculations according to our new tempo. nanosToTicks() is then set to use the
new tempo. So really our function could be nanosToTicks(x, tempo).

This is essentially what we do if we're playing a smf with a tempo change.
Presumably, what seems to concern people is an additional tempo adjustment
(e.g. pushing a button to slow playback to half speed). But this is just a
scale factor. Then we have nanosToTick(x, tempo, scale), which is the same
calculation above except that we multiply by scale at the end.

I don't really see the issue here. Or is everyone else talking about something
different?

--
7:8
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Messages in current thread:
Re: [LAD] making sense of Jack MIDI; or, is this an appropri..., M Donalies, (Sun Feb 17, 2:28 am)
Re: [LAD] making sense of Jack MIDI; or, is this an appropri..., Pedro Lopez-Cabanillas, (Fri Feb 15, 5:53 pm)
Re: [LAD] making sense of Jack MIDI; or, is this an appropri..., Pedro Lopez-Cabanillas, (Sat Feb 16, 12:16 pm)
Re: [LAD] making sense of Jack MIDI; or, is this an appropri..., Pedro Lopez-Cabanillas, (Sat Feb 16, 5:22 pm)
Re: [LAD] making sense of Jack MIDI; or, is this an appropri..., Pedro Lopez-Cabanillas, (Sat Feb 16, 9:39 am)
Re: [LAD] making sense of Jack MIDI; or, is this an appropri..., Pedro Lopez-Cabanillas, (Sat Feb 16, 10:03 am)
Re: [LAD] making sense of Jack MIDI; or, is this an appropri..., Pedro Lopez-Cabanillas, (Sat Feb 16, 11:03 am)
Re: [LAD] making sense of Jack MIDI; or, is this an appropri..., Pedro Lopez-Cabanillas, (Fri Feb 15, 7:15 pm)