Subject: Re: [linux-audio-dev] XAP: a polemic
From: Tim Goetze (tim_AT_quitte.de)
Date: Tue Dec 17 2002 - 03:33:02 EET
David Olofson wrote:
>> you absolutely need ppq for the tick system to properly map
>> different measures (5/4 time, 6/8 time etc) as per previous
>> post.
>
>I'm not sure if you absolutely need it (you *can* translate), but
>indeed, it's *much* nicer when the "speed" of musical time depends
>only on tempo, and not the whole meter.
right on.
>> add seconds-per-beat for plugins that are not limited to
>> audio purposes.
>
>How about checking the audio sample rate? (Yes, that will not map
>exactly to seconds, but it *would* allow you to have the same idea of
>"1 second" as your wordclock sync'ed audio devices, which seems much
>more useful to me.)
>
>If you want to deal with *actual* wall clock time to do some I/O,
>you're in the wrong thread (host audio thread) and/or asking the
>wrong questions, I think.
seconds_per_tick is what i actually use, and it's central
to easily mapping ticks to seconds, and from there to frames.
seconds-per-beat would be a little exotic actually, sorry
for bringing it into play.
>Anyone here ever used non-integer # of beats/bar, and/or "weird" note
>lengths?
non-integer is not proven to be needed i think. if you say you
need 9.5 beats per measure, simple make that 19 half beats. it
is a lot simpler to implement on a machine, and the denominator
is just a matter of convention but not of precision.
>> * time in seconds
>
>What time? Wall clock? If you have the current time info struct,
>it'll contain that (as calculated by the timeline "driver", based on
>audio latency), and then you can convert back and fort as you like
>by, though musical time position/"tick".
in a system where audio is the master clock, the time i mean
is simply frames / sample_rate.
>> a separate function. i have opted for the latter -- to keep
>> things sane, b.b.f conversion is only done for ticks and
>> vice versa though.
>
>Yeah, it's just that that would be a *lot* of calls if you want to
>cover all combinations. Look at VST's VstTimeInfo, or whatever Paul's
>corresponding struct in JACK is called; those cover what you need.
i don't care how complicated you make it, it just has to be
there. ;)
besides it's ok by me to complicate life for host coders.
it's the plugins that should get the better part of the deal.
tim
This archive was generated by hypermail 2b28 : Tue Dec 17 2002 - 03:36:40 EET