μ-law algorithm

The μ-law algorithm (sometimes written <a href="/facts/Mu_(letter)/j1MMkE2w">mu</a>-law, often abbreviated as u-law) is a <a href="/facts/Companding/zsfkwSzp">companding</a> algorithm, primarily used in 8-bit <a href="/facts/PCM/5gdfjtH3">PCM</a> <a href="/facts/Digital_data/JChckAvr">digital</a> <a href="/facts/Telecommunications_system/5t3Ys2DI">telecommunications systems</a> in <a href="/facts/North_America/djNjCQIl">North America</a> and <a href="/facts/Japan/U5mz0SRT">Japan</a>. It is one of the two companding algorithms in the <a href="/facts/G.711/kopBvF25">G.711</a> standard from <a href="/facts/ITU-T/9nJwkPYx">ITU-T</a>, the other being the similar <a href="/facts/A-law/PI9UC1nc">A-law</a>. A-law is used in regions where digital telecommunication signals are carried on E-1 circuits, e.g. Europe.
The terms PCMU, G711u or G711MU are used for G711 μ-law.
Companding algorithms reduce the <a href="/facts/Dynamic_range/zxcuI4Fn">dynamic range</a> of an audio <a href="/facts/Signal/41YqUJ8c">signal</a>. In analog systems, this can increase the <a href="/facts/Signal-to-noise_ratio/qohClhyG">signal-to-noise ratio</a> (SNR) achieved during transmission; in the digital domain, it can reduce the quantization error (hence increasing the signal-to-quantization-noise ratio). These SNR increases can be traded instead for reduced <a href="/facts/Bandwidth_(signal_processing)/7eMDzfJI">bandwidth</a> for equivalent SNR.
At the cost of a reduced peak SNR, it can be mathematically shown that μ-law's non-linear quantization effectively increases dynamic range by 33 dB or 5+1⁄2 bits over a linearly-quantized signal, hence 13.5 bits (which rounds up to 14 bits) is the most resolution required for an input digital signal to be compressed for 8-bit μ-law.

μ-law algorithm open-in-new

μ-law algorithm