Every time libvpx encodes a frame, it applies a transform (DCT — discrete cosine transform, the mathematical axe). It lops off high-frequency data — the visual "head" — assuming the human eye won't notice the decapitation. The frame is quantized, scarred, and compressed. The "head" (full raw data) is separated from the "body" (the compressed frame). Yet, the decoder (the Green Knight) picks up that decapitated data and reconstructs an image that is visually intact , even though mathematically mutilated.
The Green Knight (the decoder) forgives Gawain the girdle-cheat — but not entirely. He nicks Gawain’s neck. Similarly, libvpx’s rate control leaves a nick : a small, visible artifact — a ringing edge, a color shift — that proves the encoder was not perfectly honest. the green knight libvpx
Here is the deep piece. In the poem, the Green Knight offers his bare neck to Gawain’s axe. The covenant is simple: one blow in exchange for a return blow one year later. Gawain swings. The head rolls. But the Knight picks it up, remounts his horse, and rides away. Every time libvpx encodes a frame, it applies
