libvpx

libvpx is the reference software library for the VP8 and VP9 video coding formats. It is part of the WebM project and is maintained by Google and the open-source community. The library provides a stable C API for encoding and decoding video frames, along with tools for bitstream parsing, rate control, motion estimation, and intra prediction. It supports both VP8 and VP9 profiles, bit depths, and color spaces, and can operate in live encoding scenarios or offline transcoding.

The API centers on a vpx_codec interface, with context objects (vpx_codec_ctx_t) used for encoding or decoding via vpx_codec_encode and vpx_codec_decode. It also exposes image structures (vpx_image_t) for frame data and utilities for error handling and configuration. libvpx includes multithreaded encoding, tile-based parallelism, and optional SIMD optimizations (SSE2, AVX2 for x86; NEON for ARM) to accelerate performance on modern CPUs. It is designed to be portable across platforms, including Linux, Windows, and macOS, and supports various bit depths (8- and 10-bit) and sub-sampling options.

In practice, libvpx is widely used as the encoder/decoder backbone in the WebM ecosystem and in many web browsers and conferencing tools. It is distributed under a permissive license compatible with open-source and commercial use.

See also WebM, VP8, VP9, and the libvpx repository for source code and documentation.