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.