FAQ - nlp80/irFFB GitHub Wiki

FAQ

  • What does it do?

irFFB allows you to feed the 360 Hz data that's made available in telemetry to your wheel to experience the increased smoothness and fidelity that accompanies a higher FFB sample rate. Alternatively, irFFB can apply a low-latency digital filter to the standard iRacing FFB output to give you significantly smoother feedback at a minimal latency cost. irFFB can also mix in effects generated from telemetry to add additional 'texture' to your feedback.

  • Which mode should I use?

If you're after increased smoothness, extra detail and the most accurate feedback available and can live with 29 ms of latency, 360 Hz. If you would rather have a negligible latency but want to retain some of the improved smoothness, 60 Hz direct filtered.

  • Why is it necessary?

iRacing outputs FFB samples to your wheel 60 times per second. Your wheel simply applies the torque corresponding to each sample until the next sample arrives 1/60s later. This results in a 'jerky' feel and a low level of detail compared to what's available in the 360 Hz telemetry. Usually when you convert a digital representation of a signal into the analog domain you apply a filter or interpolate to achieve the best reproduction. This is particularly important at low sampling rates. The 60 Hz direct filtered mode applies a low-latency FIR to increase accuracy and improve smoothness whilst imposing only a few ms of latency.

  • What's the disadvantage of the 360 Hz FFB type?

Whilst it provides the most accurate signal to your wheel, the 360 Hz data is only available in telemetry and is actually delivered to irFFB at 60 Hz. This is because of the internal architecture of iRacing. Since telemetry is written out later during each iteration of the iRacing main loop and because irFFB has to space out the samples in time, the 360 Hz FFB type is delivered to the wheel with a latency of about 29 ms. Whilst this is a short period of time, you might find it makes a difference (or not).

  • Should I use 60 Hz direct filtered or the filters in my wheel's driver and/or firmware?

60 Hz direct filtered applies a digital FIR that's been optimised to shape the signal appropriately whilst imposing the minimum delay. It will be difficult to compare with external filters on paper unless you know how those filters have been implemented but bear in mind that all filters / interpolators must impose some latency (some more than others).

  • Why do I get an error message concerning MSVCP140.dll when I try to run irFFB?

You need to install the Microsoft VS2015 runtime.

  • Why do I have no FFB when using the direct modes?

This usually signifies that you need to recalibrate your steering in iRacing with irFFB running. If you have 'Use car specific settings' selected in iRacing, you will probably need to recalibrate your steering the first time you use each car with irFFB - it will be easier if you deselect 'Use car specific settings' in iRacing.