Interframekoding

Interframekoding, also known as interframe compression or inter-prediction, is a technique used in video coding to reduce redundancy between consecutive frames. Unlike intraframe coding, which encodes each frame independently, interframe coding exploits temporal redundancy by predicting the content of a current frame from previously encoded frames. The prediction is then transmitted as a difference, or residual, which is typically smaller than the raw frame data.

The most common interframe coding methods are motion estimation and motion compensation. Motion estimation identifies the best matching block or macroblock in a reference frame for each block of the current frame, while motion compensation reconstructs the current block using the matched reference block and a motion vector that indicates the block’s displacement. Residual information, which represents the error between the predicted block and the actual block, is encoded using transform and quantization processes similar to those used in intraframe coding.

Interframekoding can employ different types of reference frames: immediate previous frames (P-frames), bidirectional predictions from both past and future frames (B-frames), or multiple reference frames to improve prediction accuracy. Video coding standards such as H.264/AVC, H.265/HEVC, and AV1 use sophisticated interframe coding schemes to achieve compression ratios exceeding 80% compared to raw video.

The advantages of interframekoding include significantly lower bit rates for high definition and ultra-high definition video, enabling efficient storage and streaming. However, it also introduces temporal artifacts such as bleeding or ghosting when motion estimation errors occur, and is computationally more intensive, which can impact encoding and decoding latency.