videoencoding

Video encoding is the process of converting raw video into a compressed bitstream using a video codec. The goal is to reduce data size for storage and transmission while preserving acceptable visual quality. Encoded streams are suited for playback on devices or streaming over networks and are packaged into containers that carry audio. Encoding can be lossless, which preserves all information but yields large files, or lossy, which removes some data to achieve higher compression.

In the encoding process, frames are compressed by exploiting temporal and spatial redundancies. Techniques include motion estimation, transform coding, quantization, and entropy coding. Modern codecs group frames into pictures containing I-frames, P-frames, and B-frames to predict content. Subsampling of chroma information (for example 4:2:0) and color spaces such as Rec. 709 affect perceived quality. Bitrate, resolution, frame rate, and color depth are key parameters.

Common codecs include MPEG-2; H.264/AVC; H.265/HEVC; AV1; VP9; and MPEG-4 Part 2. Containers such as MP4, MKV, AVI, MOV carry video and audio streams, along with subtitles and metadata. For delivery, adaptive streaming schemes like HLS and DASH switch representations based on network conditions. Encoding can be software-based or hardware-accelerated, and can run offline for high quality or in real time for live broadcasts.

Rate control settings influence quality and size. Options include constant bitrate (CBR), variable bitrate (VBR), two-pass encoding, and CRF-based schemes that target perceptual quality. Perceptual encoding optimizes against the human visual system, helping maintain quality at lower bitrates. HDR content may use wider color gamuts and higher color depth.

In practice, video encoding enables distribution and archiving across platforms, from broadcast to streaming sites and media libraries. The choice of codec and settings reflects trade-offs among compatibility, latency, visual quality, and file size. Transcoding, or re-encoding, is often done to adapt content for different devices or networks.