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FFB Types

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nlp80 edited this page Sep 22, 2018 · 5 revisions

FFB Types

The FFB types are divided into 2 main categories; those that are based on the iRacing telemetry output and those that are based on the normal, DirectInput FFB output ('direct' modes). iRacing updates the telemetry near the end of each iteration of it's main loop (which is run 60 times per second) and the modes that are based on telemetry therefore have a minimum latency of ~ 15 ms. The minimum latency of the direct modes is the same as the normal iRacing FFB. Where approximate latencies are listed, they are referenced to the normal iRacing FFB.

  • 360 Hz - SteeringWheelTorque_ST telemetry data written out with a necessary delay to space the samples out in time. Input rate: 6 x 60 Hz / Output rate: 360 Hz. Total extra latency ~ telemetry latency + 14 ms (29 ms).

  • 360 Hz interpolated - SteeringWheelTorque_ST telemetry data with linear interpolation between samples to give 720 Hz output. Input rate: 6 x 60 Hz / Output rate: 720 Hz. Total extra latency ~ telemetry latency + 14 ms (29 ms)

  • 60 Hz direct filtered 360 - iRacing FFB direct, upsampled and passed through a low-latency digital FIR filter. Input rate: 60 Hz / Output rate: 360 Hz. Total extra latency ~ a few ms (a few ms)

  • 60 Hz direct filtered 720 - iRacing FFB direct, upsampled and passed through a low-latency digital FIR filter. Input rate: 60 Hz / Output rate: 720 Hz. Total extra latency ~ a few ms (a few ms)

The following graph shows the standard iRacing FFB, 60 Hz direct filtered 360 and the 360 Hz type with each offset in the Y axis for visibility. The offsets in the X (time) axis are an indication of the relative latencies.

From top to bottom, the traces are:

  1. (blue) Standard iRacing FFB
  2. (red) 60 Hz direct filtered 360
  3. (magenta) 360 Hz

FFB chart

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