Figure 4. Closed-loop latency and performance benchmarks.

(A) Latency between sending a command (virtual key press) and updating the display (measured using a photodiode). (A.i and A.ii) Latency depended on the frame rate of the display, updating stimuli with a delay of one to three frames. (A.iii and A.iv). (B and C) Benchmarked performance of BonVision with respect to Psychtoolbox and PsychoPy. (B) When using non-overlapping textures BonVision and Psychtoolbox could present 576 independent textures without dropping frames, while PsychoPy could present 16. (C) When using overlapping textures PsychoPy could present 16 textures, while BonVision and Psychtoolbox could present eight textures without dropping frames. (D) Benchmarks for movie playback. BonVision is capable of displaying standard definition (480 p) and high definition (1080 p) movies at 60 frames/s on a laptop computer with a standard CPU and graphics card. We measured display rate when fully pre-loading the movie into memory (blue), or when streaming from disk (with no buffer: orange; 1-frame buffer: green; 2-frame buffer: red; 4-frame buffer: purple). When asked to display at rates higher than the monitor refresh rate (>60 frames/s), the 480 p video played at the maximum frame rate of 60fps in all conditions, while the 1080 p video reached the maximum rate when pre-loaded. Using a buffer slightly improved performance. A black square at the bottom right of the screen in A–C is the position of a flickering rectangle, which switches between black and white at every screen refresh. The luminance in this square is detected by a photodiode and used to measure the actual frame flip times.

Figure 4—figure supplement 1. BonVision performance benchmarks at high frame rate.

(A) When using non-overlapping textures BonVision was able to render 576 independent textures without dropping frames at 60 Hz. At 144 Hz BonVision was able to 256 non-overlapping textures, with no dropped frames, and seldom dropped frames with 576 textures. BonVision was unable to render 1024 or more textures at the requested frame rate. (B) When using overlapping textures BonVision was able to render 64 independent textures without dropping frames at 60 Hz. At 144 Hz BonVision was able to render 32 textures, with no dropped frames. Note that these tests were performed on a computer with better hardware specification than that used in Figure 4, which led to improved performance on the benchmarks at 60 Hz. A black square at the bottom right of the screen in A and B is the position of a flickering rectangle, which switches between black and white at every screen refresh. The luminance in this square is detected by a photodiode and used to measure the actual frame flip times.