μ-law & A-law
The two companding algorithms at the heart of classic digital telephony.
Pro Audio Converter can convert audio files to and from μ-law and A-law via Core Audio. As of PAC 1.10, μ-law and A-law output is written as standard WAV for better compatibility.
μ-law — The μ-law algorithm (often u-law, ulaw, or mu-law) is a companding algorithm, primarily used in the digital telecommunication systems of North America and Japan. Companding algorithms reduce the dynamic range of an audio signal. In analog systems, this can increase the signal-to-noise ratio (SNR) achieved during transmission; in the digital domain, it can reduce quantization error (thus increasing signal-to-quantization-noise ratio). These SNR increases can be traded instead for reduced bandwidth at equivalent SNR.
A-law — The A-law algorithm is a standard companding algorithm used in European digital communications systems to optimize — i.e. modify — the dynamic range of an analog signal for digitizing. It is similar to the μ-law algorithm used in North America and Japan.