- Error Concealment

A practical error-correction method allows severe errors to remain uncorrected. However, subsequent processing - an error-concealment system - compensates for those errors and ensures that they are not audible.

There are two kinds of uncorrectable errors :

• Detected but not corrected : can be concealed with properly designed concealment methods.
• Undetected and miscorrected : cannot be concealed and might result in an audible click in the audio output.

- Interpolation

Following de-interleaving, most errors are interspersed with valid data word. It is thus reasonable to use techniques in which surrounding valid data is used to
calculate new data to replace the missing or incorrect data.

• Zero-order or pervious-value interpolation : Interpolation holds the previous sample value and replaces it to cover the missing or incorrect sample.
• First-order or linear-order interpolation : the erroneous sample is replaced with a new sample derived from the mean value of the previous and subsequent samples.
  

In many digital audio systems, a combination of zero- and first-order interpolation is used. Other higher-order interpolation is sometimes used.

- Muting

Muting is the simple process of setting the value of missing or uncorrected words to zero. Muting might be used in the case of uncorrected errors, which would otherwise cause an audible click at the output. Also in the case of severe data damage or player malfunction, it is preferable to mute the data output.

To minimize audibility of a mute, muting algorithms gradually attenuate the output signal's amplitude prior to a mute, and then gradually restore the amplitude afterward. Such muting for 1 to 4 ms durations cannot be perceived by the human ear.