[gmpi] Re: 3.9 Time Formats

  • From: Andy <andy@xxxxxxxxxx>
  • To: "'gmpi@xxxxxxxxxxxxx'" <gmpi@xxxxxxxxxxxxx>
  • Date: Sun, 15 Feb 2004 14:17:31 -0000

> -----Original Message-----
> From: Tim Hockin [mailto:thockin@xxxxxxxxxx]
> Sent: 15 February 2004 00:12
> To: gmpi@xxxxxxxxxxxxx
> Subject: [gmpi] Re: 3.9 Time Formats
> On Sat, Feb 14, 2004 at 01:06:01PM -0000, Andy C wrote:
> > 1: The abilty to get the tempo for the current sample set from the host
> ok, I think we have that covered by a use case.
> > 2: The ability to look ahead at the tempo map
> Justify this.  Give me a use case that requires it.  A general rule so far
> is "there is nothing you can know about the future that is guaranteed
> accurate" so why bother to try.  Maybe you can prove me wrong.

I doubt if I can prove you wrong as your generalized rule is correct !
However here's an example of where look ahead *may* help.   When the tempo
map changes my delay length *may* have to change to keep the delay synced to
the tempo.  At the moment, changing the delay length suddenly will cause
zipper noises. If I can look ahead in the tempo map, for the length of time
that data in the delay is valid for, I *may* be able to smooth the zipper
noise out by double buffering the delay line and switching over at the time
the tempo change happens.  At this point I'm not sure it would help but it

I fully agree though that if the user is adjusting the tempo map in real
time (say from an external controller) this would be useful.

> > 3: The ability to convert from tempo to milliseconds  from a given note
> > length.    Preferably I like to ask the host, given my current sample,
> what
> > is the tempo and what is the length in milliseconds for X note length ?
> If you know the tempo and meter, you can calculate that, right?   Can you
> give me a use case that shows the need for knowing "note length" or meter?

You are right, I'm just trying to be a lazy developer and have the host work
it out, I.E give me a midi ticks to millisecond converter and save me the
trouble of asking about the map, the meter and the sample rate to do the
calculations myself.

> > 4: Given the ability to "look ahead" in the tempo map, I'd like to do
> the
> > same calculation for any point on the tempo map (in case my plugin needs
> to
> > do tempo look ahead for some reason)
> use case?

I'm less sure about this, but for none user-real-time play how about the
following.  Suppose I have a tempo synched LFO of complex waveform.  I want
to calculate the waveform and store it in a lookup buffer, based on the
tempo.  Using look ahead I could space the calculations (rather than one big
burst) so the wave was ready JIT for the tempo change.  Any good ?

Andy C

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