dcshift

Apply a DC shift to the audio.

This can be useful to remove a DC offset (caused perhaps by a hardware problem in the recording chain) from the audio. The effect of a DC offset is reduced headroom and hence volume. The astats filter can be used to determine if a signal has a DC offset.

'shift'

Set the DC shift, allowed range is [-1, 1]. It indicates the amount to shift the audio.

'limitergain'

Optional. It should have a value much less than 1 (e.g. 0.05 or 0.02) and is used to prevent clipping.