This block is a deeper technical dive into the internal architecture of modern video codecs. It explains what actually happens inside an encoder: how frames are split into blocks, how intra- and inter-frame prediction work, how motion estimation finds similarities between frames, and how I-, P-, and B-frames form a GOP structure. Readers also learn about transform coding, quantization, coefficient scanning, entropy coding, in-loop filtering, rate control, and rate-distortion optimization. The goal is to make the encoder’s decision-making process understandable: how it chooses prediction modes, where quality is lost, how bitrate is allocated, and why slower encoding can often produce smaller files at the same visual quality.