Deinterlacing

Deinterlacing is the process of converting interlaced video into a progressive scan format. Interlaced video encodes each frame as two fields captured at different moments, top and bottom fields, which are displayed alternately. Deinterlacing either combines these fields or reconstructs full frames so they can be displayed on progressive-scan devices such as computer monitors and modern televisions.

The simplest methods are bob and weave. Bob deinterlacing treats each field as a separate frame, resulting in smooth motion but halved vertical resolution. Weave combines two fields from the same frame, preserving resolution but can produce combing artifacts when motion occurs between fields.

More advanced approaches use motion estimation to align fields and interpolate missing lines. Adaptive deinterlacing selects methods based on detected motion: static areas may be processed with weaving or spatial interpolation, while moving areas use motion-compensated interpolation. Motion-compensated deinterlacing (MCID) can produce high quality results but requires more processing power. Many implementations use predefined algorithms such as YADIF (Yet Another De-Interlacer) or EEDI2, sometimes with temporal or edge-directed filtering to reduce artifacts.

Artifacts and limitations: improper deinterlacing can cause combing, blurring, tearing, or flicker. The choice of method involves a trade-off between sharpness, temporal stability, and computational requirements. Real-time deinterlacing is essential in broadcast and consumer playback, often supported by hardware decoders or GPUs.

Applications: deinterlacing is used to display legacy interlaced content on progressive displays, in DVD and Blu-ray players, streaming pipelines, and live television processing.