In our previous article and video, I introduced you to our upcoming testing methodology for evaluating graphics cards based not only frame rates but on frame smoothness and the efficiency of those frame rates. I showed off some of the new hardware we are using for this process and detailed how direct capture of graphics card output allows us to find interesting frame and animation anomalies using some Photoshop still frames.
Today we are taking that a step further and looking at a couple of captured videos that demonstrate a "stutter" and walking you through, frame by frame, how we can detect, visualize and even start to measure them.
This video takes a couple of examples of stutter in games, DiRT 3 and Dishonored to be exact, and shows what they look like in real time, at 25% speed and then finally in a much more detailed frame-by-frame analysis.
Obviously this is just a couple instances of what a stutter is and there are often times less apparent in-game stutters that are even harder to see in video playback. Not to worry - this capture method is capable of seeing those issues as well and we plan on diving into the "micro" level as well shortly.
We aren't going to start talking about whose card and what driver is being used yet and I know that there are still a lot of questions to be answered on this topic. You will be hearing more quite soon from us and I thank you all for your comments, critiques and support.
Let me know below what you thought of this video and any questions that you might have.
A change is coming in 2013
If the new year will bring us anything, it looks like it might be the end of using "FPS" as the primary measuring tool for graphics performance on PCs. A long, long time ago we started with simple "time demos" that recorded rendered frames in a game like Quake and then played them back as quickly as possible on a test system. The lone result was given as time, in seconds, and was then converted to an average frame rate having known the total number of frames recorded to start with.
More recently we saw a transition to frame rates over time and the advent frame time graphs like the ones we have been using in our graphics reviews on PC Perspective. This expanded the amount of data required to get an accurate picture of graphics and gaming performance but it was indeed more accurate, giving us a more clear image of how GPUs (and CPUs and systems for that matter) performed in games.
And even though the idea of frame times have been around just a long, not many people were interested in getting into that detail level until this past year. A frame time is the amount of time each frame takes to render, usually listed in milliseconds, and could range from 5ms to 50ms depending on performance. For a reference, 120 FPS equates to an average of 8.3ms, 60 FPS is 16.6ms and 30 FPS is 33.3ms. But rather than average those out by each second of time, what if you looked at each frame individually?
Scott over at Tech Report started doing that this past year and found some interesting results. I encourage all of our readers to follow up on what he has been doing as I think you'll find it incredibly educational and interesting.
Through emails and tweets many PC Perspective readers have been asking for our take on it, why we weren't testing graphics cards in the same fashion yet, etc. I've stayed quiet about it simply because we were working on quite a few different angles on our side and I wasn't ready to share results. I am still not ready to share the glut of our information yet but I am ready to start the discussion and I hope our community find its compelling and offers some feedback.
At the heart of our unique GPU testing method is this card, a high-end dual-link DVI capture card capable of handling 2560x1600 resolutions at 60 Hz. Essentially this card will act as a monitor to our GPU test bed and allow us to capture the actual display output that reaches the gamer's eyes. This method is the best possible way to measure frame rates, frame times, stutter, runts, smoothness, and any other graphics-related metrics.
Using that recorded footage, sometimes reaching 400 MB/s of consistent writes at high resolutions, we can then analyze the frames one by one, though with the help of some additional software. There are a lot of details that I am glossing over including the need for perfectly synced frame rates, having absolutely zero dropped frames in the recording, analyzing, etc, but trust me when I say we have been spending a lot of time on this.
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