Paul Davis wrote:
>>>I'm just starting to write my first alsa-lib midi applications. I'm
>>>wondering what the acronym ppq stands for and what it means (especially
>>>in relation to tempo). Unfortunately, I didn't find any docu on the
>>>topic of tempo.
>
>> int ppq; /* time resolution, ticks/quarter */
>
> [ ... ]
>
>>the value is usually synonymous to the 'division' of a standard midi
>>file.
>
>"ppq" stands for "parts per quarter". as the header file suggests
>without much explanation, its length of a quarter note expressed in
>clock ticks. if the meter is 4/4 and the tempo is 120bpm, then a
>quarter note lasts 0.5 seconds. if the clock used for timing ticks 100
>times per second, there are 50 clock ticks per quarter note, so
>ppq=50.
though usually it will be a number divisible by 3 and 4 to make
triplets and even beats alike coincide with integer ticks. cubase
on the atari used to set this to 192, though some do prefer 480 or
even more to allow for minute timing ('groove') adjustments.
tim
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