Author Topic: Flicks: very small unit of time for C++  (Read 1449 times)

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JeGX

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Flicks: very small unit of time for C++
« on: January 26, 2018, 12:24:46 PM »
Quote
When working creating visual effects for film, television, and other media, it is common to run simulations or other time-integrating processes which subdivide a single frame of time into a fixed, integer number of subdivisions. It is handy to be able to accumulate these subdivisions to create exact 1-frame and 1-second intervals, for a variety of reasons.

Knowing that you should never, ever use floating point representations for accumulated, simulated time (lest your temporal accuracy degrade over time), the std::chrono time tools in C++ are ideal. However, the highest usable resolution, nanoseconds, doesn't evenly divide common film & media framerates. This was the genesis of this unit.


A flick (frame-tick) is a very small unit of time. It is 1/705600000 of a second, exactly.

1 flick = 1/705600000 second

This unit of time is the smallest time unit which is LARGER than a nanosecond, and can in integer quantities exactly represent a single frame duration for 24 Hz, 25 Hz, 30 Hz, 48 Hz, 50 Hz, 60 Hz, 90 Hz, 100 Hz, 120 Hz, and also 1/1000 divisions of each, as well as a single sample duration for 8 kHz, 16 kHz, 22.05 kHz, 24 kHz, 32 kHz, 44.1 kHz, 48 kHz, 88.2 kHz, 96 kHz, and 192kHz, as well as the NTSC frame durations for 24 * (1000/1001) Hz, 30 * (1000/1001) Hz, 60 * (1000/1001) Hz, and 120 * (1000/1001) Hz.

That above was one hell of a run-on sentence, but it's strictly and completely correct in its description of the unit.

This makes flicks suitable for use via std::chrono::duration and std::ratio for doing timing work against the system high resolution clock, which is in nanoseconds, but doesn't get slightly out of sync when doing common frame rates.

We also support some common audio sample rates as well. This list is not exhaustive, but covers the majority of digital audio formats. They are 8kHz, 16kHz, 22.05kHz, 24kHz, 32kHz, 44.1kHz, 48kHz, 88.2kHz, 96kHz, and 192kHz.

Though it is not part of the design criteria, 144 Hz, which some newer monitors refresh at, does work correctly with flicks.


Link: https://github.com/OculusVR/Flicks