Subject: Re: sequencer timing issues
From: Paul Barton-Davis (pbd_AT_Op.Net)
Date: ke loka 27 1999 - 14:29:02 EDT
[ why softwerk can't use a kernel sequencer ]
>Hmm..sounds like you're already paying much of the price of the
>hyperseq approach..might as well go all the way. :)
thats the plan, just as soon as i:
* finish autoconf-izing Quasimodo
* fix Quasimodo's audio input system
* finish writing a prototype of my take on the plugin API
* port the ALSA CS4231 driver to pcm-v2
* port SoftWerk to Gtk--
etc. etc. :)
>> in SoftWerk's case, because it doesn't process audio data in any way,
>> I use sigitimer(2) to give me a periodic async signal every so often
>> (typically 20-100ms: its controllable in the UI). i use this to
>> measure the passage of time, and compute when a beat/tick is
>> happening. soon, i will use the RTC with select(2), which will be
>> more accurate and permit much faster tempos than sigitimer can.
>
>Wouldn't you say that an HZ > 100 kernel is the cleanest solution?
its the cleanest, but not the best. HZ = 1000 adds about 8% overhead
to IRQ processing *all the time*. and even then, the system timer is
only accurate to 1ms, which is still not adequate for some envisioned
uses of SoftWerk (though given its use of h/w MIDI ports and the speed
of MIDI communication, its pretty excellent for 99% of them :)
--p
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