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killown edited this page Mar 16, 2026 · 1 revision

Metric: FTV (Frame Time Variance)

Executive Summary

FTV measures the consistency of frame durations. Instead of looking at raw speed, it looks at the "jitter" between the current frame and the previous one. To be technically accurate, FTV must be interpreted as a percentage of your ideal ms.

Why this number matters

Consistency is often more important than raw speed. A locked 60 FPS with 0% FTV feels better than a 120 FPS stream with 20% FTV.

  1. The Human Eye: We are evolved to detect changes in velocity. If an object moves 10 pixels, then 12 pixels, then 8 pixels in the same time interval, it looks "nervous." FTV quantifies this nervous energy.
  2. The Micro-Stutter Detector: FTV captures "hiccups" that last only a single frame, the kind that disappear in a 1-second FPS average.

How to read the numbers (Relative to Budget)

FTV % of Interval Perception Technical Reality
0% - 5% Liquid Normal OS jitter and kernel interrupt noise.
5% - 15% Textured Minor background contention; usually acceptable for non-pro gaming.
15% - 25% Jittery Perceptible "oily" motion. The system is fighting for resources.
> 25% Stuttering Major hitching. Likely shader compilation or heavy CPU interrupts.

FTV vs. Delta ms

  • delta ms is your velocity (how fast are we going?).
  • FTV is your acceleration jitter (is the speed changing?).

A 2ms FTV on a 60Hz screen (16.6ms budget) is a minor 12% variance, totally fine. A 2ms FTV on a 240Hz screen (4.1ms budget) is a massive 48% variance, unusable.

Troubleshooting

  • Sawtooth Pattern: If FTV toggles between two fixed values, your frame-pacer is likely fighting with the OS VSync.
  • Random Spikes: Usually "Stop-the-world" events like garbage collection, disk I/O on the main thread, or thermal throttling.
  • High Constant FTV: Often caused by "Windowed Mode" where the compositor is applying its own variable delay on top of your app.

The Goal

For a professional simulation, keep FTV under 5% of your target interval. When variance is kept this low, the digital motion achieves "analog" smoothness.

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