ljudcodec

ljudcodec, or audio codec, is a software algorithm or hardware module that encodes and decodes digital audio data. Its job is to compress audio for storage or transmission and to reconstruct it for playback. Codecs can be lossless (e.g., FLAC, ALAC, WAV PCM) or lossy (e.g., MP3, AAC, Ogg Vorbis, Opus). Lossless codecs preserve the exact original signal, while lossy codecs discard some information to reduce bitrate.

Encoding typically involves transforming the input signal into a more compact representation using techniques such as linear prediction, transform coding (e.g., MDCT), and perceptual models that exploit masking and auditory thresholds. The resulting bitstream is characterized by its bitrate, format, and latency. Decoding reverses the process to reconstruct a playable audio signal.

Common usage includes streaming services, digital music players, video compression pipelines, and real-time communications. Latency and error resilience are important considerations for interactive applications such as VoIP and online gaming. The choice of codec affects audio quality, bandwidth requirements, device compatibility, and licensing.

Many codecs are standardized or patented. MP3 and AAC are widely used but subject to licensing royalties. Opus is a modern, royalty-free IETF standard designed for both speech and music with low latency. Open-formats such as FLAC are lossless and widely used where fidelity is essential.

Sampling rates and bit depths vary, but typical consumer scenarios use 44.1 or 48 kHz with 16-24 bits. Compatibility between encoders, decoders, and containers affects interoperability.