fre:ac is a mature, cross-platform audio converter and CD ripper with a plugin-based component architecture. The system is built on the BoCA framework and smooth GUI library, providing both a graphical interface (freacGUI) and a command-line interface (freaccmd). In production it handles audio format conversion (MP3, AAC, FLAC, Opus, WMA, etc.), CD ripping with freedb/CDDB metadata lookup, AccurateRip verification, tag editing, and even YouTube/Vimeo video downloading via JavaScript-based site scripts. The codebase is extensive (906 files) with heavy use of the BoCA component system for decoders, encoders, DSP processors, verifiers, and extensions. Key entry points are src/loader/gui.cpp and src/loader/console.cpp. The architecture follows a job-based conversion pipeline with worker threads, progress reporting, and configuration persistence. Internationalization is comprehensive (40+ languages). While the code demonstrates solid engineering with signal/slot decoupling and reusable components, it carries technical debt from legacy V8 API usage, manual memory management, and platform-specific #ifdefs.
qaac is a command-line audio encoder that uses Apple's CoreAudioToolbox (or the reference ALAC encoder) to encode audio to AAC or ALAC formats. It supports a wide range of input formats (WAV, FLAC, WavPack, Opus, Ogg Vorbis, CAF, and more) via runtime-loaded codec libraries, and outputs to MP4/M4A, ADTS, CAF, WAV, or raw PCM. The architecture follows a clean pipeline pattern: input sources implement the ISource interface, pass through optional DSP filters (resampler, normalizer, limiter, compressor, matrix mixer, etc.), and are written to output sinks. Metadata handling is integrated via vendored taglib, and the encoder supports gapless encoding, chapter markers, artwork, and various tagging formats. The codebase is predominantly C++ with platform-specific adaptations for Windows and macOS, and includes several reusable utility components such as a streaming FFT convolver, ring buffer, and cross-platform dynamic library loader.