FCAT Frame Analysis

Frametime and latency performance

With FCAT we will look into Frame Experience Analysis. Basically with the charts shown we are trying to show you graphics anomalies like stutters and glitches in a plotted chart. There has been a measurement introduced, latency measurements. Basically, it is the opposite of FPS.  

• FPS mostly measures performance, the number of frames rendered per passing second.
• Frametime AKA Frame Experience recordings mostly measures and expose anomalies - here we look at how long it takes to render one frame. Measure that chronologically and you can see anomalies like peaks and dips in a plotted chart, indicating something could be off. 

We have a detailed article (read here) on the new FCAT methodology used, and it also explains why we do not use FRAPS anymore. Frametime - Basically the time it takes to render one frame can be monitored and tagged with a number, this is latency. One frame can take say 17 ms. Higher latency can indicate a slow framerate, and weird latency spikes indicate a stutter, jitter, twitches; basically, anomalies that are visible on your monitor.

What Do These Measurements Show?

What these measurements show are anomalies like small glitches and stutters that you can sometimes (and please do read that well, sometimes) see on screen. Below I'd like to run through a couple of titles with you. Bear in mind that Average FPS often matters more than frame-time measurements. 

For this interested, in the above video, you can see the actual FRAPS recording, each frame rendered gets a color label so that we can analyze the scene tested. Each run is 30 seconds precisely. 

Above a percentile chart, this plot is a 31-second recording @ 2560x1440. Here we plot relative FPS and place it in relation to percentiles. 50% of the time measured frames is the average framerate (higher = better). Today we'll use a Radeon RX 580 and a GeForce GTX 1060. Often the two card are close to each other in performance, for this game, NVIDIA is faster overall. A level line means that a lot of frames are in the same framerate, so this is looking pretty solid!

With frametime chart, lower = better. Huge spikes above 40 ms to 50 ms can be considered a problem like a stutter or indicate a low framerate. You can see (and many who have tried the demo), you'll get the occasional stutter with this game. Other than a few drops, the frametimes looks very good overall. 

For the Radeon, we also see the very similar behavior. Our run also exhibits a few stutters and framedrops. While stutters aren't fun, the overall pacing looks pretty good. Let's overlay the two:

And combined with an overlay, the cards both do look fairly similar towards each other aside from lower latency for the GTX 1060. For both, it could be better (stutters), but this is definitely game engine related.