Framerate Isn't Good Enough: Latency Pipeline, 'Input Lag,' Reflex, & Engineering Interview

This engineering interview & discussion follows-up our previous industry interviews with people like Tom Petersen of Intel and Bill Alverson of AMD, but now featuring Guillermo Siman of NVIDIA, who joins to discuss the engineering aspects of latency. We've recently been talking about an increase in our focus in testing on latency, adding to our existing FPS benchmarks, and this discussion is to help provide an educational backdrop on what truly comprises end-to-end system latency. We'll focus on the latency pipeline, educational topics such as how the game engine handles and processes input, peripheral latency, and system-level latency (such as from the render queue). These topics also cover various types of bottlenecks.



TIMESTAMPS

00:00 - Latency Testing & Engineering Interview
02:40 - Latency Pipeline Canonical View
08:55 - Common Misconceptions
11:32 - Types of "Lag" & Bottlenecks Explained
14:50 - Game Engine Input Sampling
20:39 - Impact of GPU Bottlenecks & Reflex
26:07 - Summarizing

** Please like, comment, and subscribe for more! **

Links to Amazon and Newegg are typically monetized on our channel (affiliate links) and may return a commission of sales to us from the retailer. This is unrelated to the product manufacturer. Any advertisements or sponsorships are disclosed within the video ("this video is brought to you by") and above the fold in the description. We do not ever produce paid content or "sponsored content" (meaning that the content is our idea and is not funded externally aside from whatever ad placement is in the beginning) and we do not ever charge manufacturers for coverage.

Follow us in these locations for more gaming and hardware updates:


Host: Steve Burke
Guest: Guillermo Siman
Camera, Editing: Vitalii Makhnovets, Mike Gaglione

[GamersNexus]

Awesome engineering discussion with Guillermo. He definitely joins the list of some of the most educational interviews we've hosted. Looking forward to exploring this topic more!

[GuilleSiman]

Thanks so much for having me on! Great to meet you and the team—that was loads of fun. Looking forward to Pt. 2 with n0thing!

[JosefSpjut]

One clarification to the answer to Steve's question at around 22:30. The input sampling is a "uniform random" variable with an average time of 5 ms in that example. This is because as Guillermo explained earlier, the input could have arrived anywhere from 0 to 10 ms before the frame, so the sampling causes an average of 5 ms of latency, though any particular frame has a roughly equal probability of being any value from 0 to 10 ms.

[TheJonazas]

This is what I've been saying for 10 years now. I never understood why no one ever cared about input lag. It is SO important.

[TomatePasFraiche]

Battlenonsense being cited in this video warmed my heart.
Great video with great insights!

[ultrachocobo]

I really enjoy the shoutout to battlenonsense and that they learned from that. Really humble, likeable guy who explains it well.

[techfusionaz]

Thank you for looking at this. Latency is definitely the most underrated metric when measuring system performance right now. I purposefully optimize my graphics settings to get the lowest amount of input lag possible, rather than going for more FPS.

[iamgates]

I’m a consultant in the advanced technology space and have to give technical “talks” for a living - this was great. It’s really hard to explain technical complexity in a way that is accessible; it’s all abstraction of language we are dealing with so things get confusing quickly. This audience is likely much more technical than most, however thats still very cool something this in depth and a bit esoteric has 200k views. Solid work. Looking forward to Pt 2!

[Cory_]

The animations showing the render queue in GPU bound and CPU bound situations was really great. It clarified some things that I had always wondered.

[Xarthis]

I really like that you do these deep background pieces, they give the required context to understand your also excellent hardware reviews.

[HenryThe]

I love listening to people who love and care about what they do talk about their work, especially highly technical things being explained in a more accessible way. Great stuff from the both of you, this video was really cool.

[Bob-of-Zoid]

Latency is not just a gaming thing! It's of utmost importance for professional audio and video recording too, so not only a graphics thing. Imagine recording like 15 microphones to separate tracks simultaneously, with EQ and many other effects on each, and the whole, and slamming it on a drive, as close to real time to be able to monitor it all! Same goes for recording scenes with many cameras, all at once, or even editing live between them.

Please do more on the subject Steve, and also give it more love from a processor/RAM... perspective.

[ethanlee]

Fantastic coverage on this underrated metric. It felt very enjoyable to watch and not at all 'lecture-esque' as you thought it would be! Thanks for the great video and awesome content :D

[Halvkyrie]

I'm really glad that latency is getting so much focus these days honestly. For a long time i feel like it's not really been talked about much, despite being so critical for the user experience

[nathanmccormack]

Fantastic video, the guy from Nvidia was an absolute pleasure to listen to and very professional. I now understand why when I run with reflex on my game runs so much smoother. Look forward to part 2. Thanks Steve and team

[stevekristoff]

Glad that you're starting to look into this. Though this is MUCH larger than just for graphics. I.e. a very good example is storage (nvme/ssd/hdd); memory access; as well as general interrupt handling delays. The biggest item I run into pretty much daily is data subsystem performance (drive I/O basically). This is made worse as basically OEM's and all reviewers seem to be fascinated by 'streaming throughput' to a subsystem when this workload basically is completely non-existent for any real world workload. (anyone who doubts this, load up diskmon and check for yourself, it doesn't exist). Wish you can add similar level of detail to any reviews you do with these other subsystems.

[mrhappytroll]

Really neat to see how reflex works at the end there

[CheapBastard]

Latency testing would be such a great addition to the testing of hardware. Especially with the introduction of frame generation, but also for CPU overhead, driver overhead, OS overhead and human input devices. We generally mainly know latency from monitor testing. It won't be easy though.

[Retr_ofwgkta]

very educational video, i've been playing fps games for years but never really put lots of thought into how it all worked. really good to know

[brianbaker]

Especially with higher polling rates being more and more common, latency deep dives are super necessary