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List:       linux-sound
Subject:    Re: sequencer timing issues
From:       Paul Barton-Davis <pbd () Op ! Net>
Date:       1999-10-27 17:55:58
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  [ 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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