[gmpi] Re: Topic 6: Time representation
- From: "gogins@xxxxxxxxxxxx" <gogins@xxxxxxxxxxxx>
- To: gmpi@xxxxxxxxxxxxx
- Date: Tue, 29 Apr 2003 10:43:43 -0400
I think the idea of a union containing different time representations is
good. I think it should be bars/beats, SMPTE, absolute seconds from
beginning of performance, sample frames, MIDI ticks. Representations that
naturally are integers should be size_t or long, those that can be
fractions should be floating point numbers, preferably double-precision.
GMPI itself should contain the conversion routines.
But the BASIC time, the low-level representation used for scheduling,
should be absolute seconds from beginning of performance.
Time should additionally be represented as a series of points, and each
point should have a spline for interpolation between the points. GMPI
should implement linear, cubic, and Hermite interpolation and allow for
user-defined splines.
Original Message:
-----------------
From: RonKuper@xxxxxxxxxxxx
Date: Tue, 29 Apr 2003 08:57:04 -0400
To: gmpi@xxxxxxxxxxxxx
Subject: [gmpi] Topic 6: Time representation
Is time represented as samples or "ticks" or both/neither? How are
discontinuities in the timeline expressed?
My stake in the ground is that we need a way to represent time either in
musical units or absolute units. The units should be chosen in such a way
to avoid rounding errors when converting from one to the other, and should
also support at least 24 hours of time range.
By way of example, SONAR uses a representation where a 64-bit structure can
represent either a floating point absolute time, or an integer musical time
in units of 960*(2^16) PPQN. (The choice of PPQN makes conversions to a
user editable 960 PPQN efficient.) Conversions are done via a host supplied
time converter interface.
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