frameadvance

Frame advance is a feature in video game emulation and other interactive simulations that permits stepping through execution one frame at a time. By pausing the simulation and advancing only a single frame per input, it enables precise observation of rendering, input handling, and timing. The capability is especially valuable for debugging graphical glitches, timing bugs, and for analyzing frame-by-frame behavior in tools used for research and development.

In typical implementations, the user issues a frame-advance command while the emulator is paused or in a special stepping mode. The core renders one frame, processes inputs, and then returns to a paused state. Some emulators achieve this by saving a checkpoint and restoring it after each frame, ensuring deterministic frame-by-frame progress, while others advance a single frame in the active state.

Frame advance is widely used in tool-assisted speedruns (TAS), where developers and analysts reproduce exact frame sequences to study game logic, frame timing, or to generate frame-perfect inputs. It is also used for debugging, documentation, and the capture of frame-accurate video or image sequences for demonstrations and testing.

Limitations include reliance on deterministic emulation; any non-deterministic behavior or randomized memory access can introduce inconsistencies. Additionally, some games rely on precise mid-frame interrupts or audio timing that may not be captured with simple frame stepping, and input lag considerations can affect analysis.

Historically, frame stepping emerged alongside emulation debugging tools and has become a standard feature in many modern emulators, including popular platforms such as BizHawk, RetroArch, MAME, and various console-specific cores.