[linux-audio-dev] XAP: a polemic

Tim Goetze tim at quitte.de
Mon Dec 16 15:38:03 UTC 2002


Paul Davis wrote:

>>>just imagine two different timelines, one in 6/8, the other in 5/4,
>>>both at different tempos. one delay plugin uses one of them, another
>>>uses the other. neither of these timelines are uniform across the
>>>system, yet plugins with tempo-synced parameters need to care about
>>>(at least one of) them. right?
>>
>>you can, without loss of information, express both as ticks, 
>>and you're back to the uniform timebase. 
>
>how so? if ticks are constant-per-beat, i don't see how they can
>express the information without the additional beat-per-second
>value(s). if ticks are constant-per-second, i don't see how they can
>express the information without the additional ticks-per-beat
>value(s). any tempo-synced element to an XAP plugin needs to translate
>a musical time/duration to a tick value (and thence to audio frame
>units). doing this requires two pieces of information, one of which is
>not constant across all musical timelines.

ticks are constant per quarter in a sane setup.

>>many uses of tempo-sync only make use of small note lengths
>>(16th, 8th triplet etc) so they do not need this mapping.
>
>i don't think that the note length affects this in any way. 

sorry for being unprecise: a quarter note is 192 ticks. for
example. a plugin is generating 8th note pulses. it simply 
plays where (tick % 96) == 0.

tim





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