How to Force Aligned Keyframes Across ABR Ladder Renditions Using FFmpeg

Misaligned keyframes across ABR renditions can cause micro-freezes during quality switches, even when rebuffering metrics show zero issues. The root cause is that FFmpeg's default scene-cut detection inserts keyframes at content-driven moments, leading different renditions to place keyframes at different timestamps. The fix involves locking a fixed GOP size by setting keyint equal to min-keyint, disabling scene-cut detection, and applying a time-based force_key_frames expression consistently across every rung of the ladder. For hardware encoders like NVENC, the -g flag replaces x264-specific options while the forced-keyframe expression handles exact placement. Alignment can then be verified using ffprobe to compare keyframe timestamps across renditions, ensuring all rungs share an identical keyframe grid.