libde265 is a robust, LGPL-licensed C library implementing the H.265/HEVC video codec standard. It provides a full decoder (Main profile with range extensions) and an experimental encoder. The library is designed for integration into media software (e.g., libheif, GStreamer, VLC) and includes a clean C API (de265.h) for decoding and a similar API for encoding. Internally, it features a modular architecture with SIMD acceleration for x86 (SSE4.1, AVX2, AVX512) and ARM (NEON), a branchless CABAC decoder, multi-threading via WPP and tiles, and a function-pointer-based acceleration abstraction. Example applications include a command-line decoder (dec265), encoder (enc265), and a Qt-based visual debugger (sherlock265). The codebase is actively maintained with CI/CD, fuzzing, and conformance testing, though the encoder remains experimental with incomplete features. The library is production-grade for decoding and has been battle-tested by downstream projects.
This repository is a comprehensive Go library for geometric data structures and operations. It provides implementations of OGC-standard geometry types (Point, LineString, Polygon, MultiPoint, MultiLineString, MultiPolygon, GeometryCollection) with support for 2D, 3D, and measured dimensions. The library includes algorithms for computational geometry (area, centroid, convex hull, line intersection, etc.) and encoders/decoders for formats like WKT, WKB, GeoJSON, KML, and IGC. Architecture is modular: core `geom` package defines types and interfaces, `xy`/`xyz` packages handle planar/spatial algorithms, `encoding/*` packages manage format serialization, and utilities like `transform` and `sorting` offer reusable helpers. Command-line tools for IGC parsing and PostGIS integration demonstrate practical usage. The code emphasizes clean separation of concerns, interface-driven design, and thorough testing including property-based and fuzzing tests.
This repository is the official reference implementation of the VP8 and VP9 video codec standards (libvpx), maintained by the WebM project. It provides a C library for encoding and decoding VP8/VP9 video streams, with support for multiple container formats (IVF, WebM, Y4M), real-time and two-pass encoding, scalable video coding (SVC), and high-bit-depth profiles (10/12-bit). The architecture is a classic monolithic codec library: a public API layer (`vpx_codec_*` functions) dispatches to internal encoder/decoder state machines, which in turn call a large set of DSP primitives (transforms, quantization, motion estimation, loop filtering, entropy coding) implemented in both portable C and heavily optimized SIMD for x86 (SSE2/SSE4/AVX2/AVX512), ARM (NEON, SVE), MIPS (MSA, DSPR2), PowerPC (VSX), and LoongArch (LSX). The build system uses custom `.mk` files with runtime CPU detection (RTCD) to select the appropriate function pointer at runtime, enabling a single binary to run across diverse hardware. The primary data flow is frame-by-frame: raw YUV frames enter the encoder, are transformed, quantized, entropy-coded, and output as a bitstream; the decoder reverses the process. Rate control models buffer fullness and scene complexity to meet target bitrates. The codebase includes extensive Google Test-based unit tests covering algorithm correctness, bitstream conformance, and performance benchmarks. Example applications (`vpxenc`, `vpxdec`, `simple_encoder`, `simple_decoder`) demonstrate the API and serve as integration tests. Key entry points include `vpx_codec_enc_init()`, `vpx_codec_encode()`, `vpx_codec_dec_init()`, `vpx_codec_decode()`, and the control interface (`vpx_codec_control_`). External dependencies are minimal (only standard C library and optional platform headers); third-party code includes Google Test, libwebm (WebM mux/demux), libyuv (color conversion, bundled), and x86inc.asm (NASM macros). The repository also contains research-oriented tools under `tools/3D-Reconstruction/` (Python/Processing sketches for motion estimation and 3D reconstruction) which are experimental and not part of the core library.
Apache Commons Codec is a mature Java library providing a comprehensive set of encoders and decoders for binary-to-text formats (Base16, Base32, Base64, Base45, Base58, Hex), digest and hash algorithms (MD5, SHA-1/2/3, MurmurHash, XXHash32, Blake3, CRC16/32), phonetic encoding (Soundex, Metaphone, Caverphone, Beider-Morse, Daitch-Mokotoff), and network codecs (URL encoding, Quoted-Printable, RFC 1522 MIME). The architecture is modular with clear package separation: `binary`, `digest`, `language`, `net`, and `cli`. Key design patterns include a builder pattern for configuring codecs (e.g., `Base64.builder()`), an abstract base class `BaseNCodec` with streaming support via `BaseNCodecInputStream`/`OutputStream`, and a `CodecPolicy` enum for strict vs. lenient decoding. The library has no production dependencies; only test dependencies on commons-lang3 and commons-io. It is widely used across the Java ecosystem, with extensive test coverage including RFC vectors and backward compatibility tests. However, some deprecated methods and known bugs (e.g., in MurmurHash3 legacy methods) are preserved for compatibility, and certain algorithms (SHAKE) require Java 25, introducing version drift.
ZXing (Zebra Crossing) is a mature, multi-format barcode image processing library written in Java. It provides both decoding and encoding capabilities for over 15 1D and 2D symbologies, including QR Code, Data Matrix, Aztec, PDF417, UPC/EAN, Code 128, and many more. The core library is platform-independent, with additional modules for Android (Barcode Scanner app), Java SE (command-line tools), and web applications (a decode servlet and a GWT-based generator). The architecture follows a clean Reader/Writer interface pattern, with format-specific implementations decoupled from common infrastructure like Reed-Solomon error correction, binarization, and perspective transformation. The library is in maintenance mode: no new features are planned, but bug fixes and minor enhancements from the community are accepted. The Android app is deprecated and does not work on Android 14. Despite its age, the codebase remains a reference implementation for barcode standards and is widely ported to other languages.