Companding

What is companding?
Companding refers to a technique of compressing and then expanding (or decompressing) an analog or digital signal. It is a combination of the words 'compress' and 'expand'.

This two-sequential process is overall non-linear, but linear over short periods of time. Data is compressed before it is transmitted. It is then expanded at the receiving end to return it to its original shape using the same non-linear scale, but with reduced noise and crosstalk levels (which means reduced interruption or disturbance of signals in an adjacent circuit). This disturbance or disturbance is usually caused by alternating current (AC), direct current (DC), or other transmission lines.

The electronic circuit that is responsible for companding is called a compandor.

This term is also known as complement.

Companding wird als Ergänzung zum Modulations- und Demodulationsvorgang verwendet. Bei diesem Vorgang wird ein Sprachsignal komprimiert, von analog auf digital umgestellt, übertragen und von digital auf analog zurückgewandelt, bevor es wieder erweitert wird. Diese Prozesse sind in der ITU-Empfehlung G.711 des ITU-Standardisierungssektors für Telekommunikation beschrieben.

For analog audio signals, the amplitude of weak signals is increased and the amplitude of strong signals is decreased, thereby changing (compressing and expanding) the dynamic range of the signals. The technique is used in AM, FM and SSB modulation radio and is helpful in improving the quality of amplified voices and musical instrument sounds. Dolby and dbx noise reduction also use companding. Concert audio systems and noise reduction technologies like dbx and Dolby use a triplet of amplifiers to accomplish this process, meaning a logarithmic amplifier, a linear variable gain amplifier, and an exponential amplifier.

Pulse code modulation (PCM) companding is used for digital audio signals. This process reduces the number of bits used to record the strongest (loudest) signals. In the digital file format, companding improves the signal-to-noise ratio at reduced bit rates. For example, a 16-bit PCM signal can be converted to an eight-bit '.wav' or '.au' file.

Another application of companding involves professional wireless microphones that have a greater dynamic range than can be achieved by radio transmission. By reducing the amplitude of signals, the signals can be transmitted and then expanded at the receiver where the original signals are reproduced by the receiving electronic device.

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