Adjust the input audio volume.

The filter accepts exactly one parameter vol, which expresses how the audio volume will be increased or decreased.

Output values are clipped to the maximum value.

If vol is expressed as a decimal number, the output audio volume is given by the relation:

output_volume = vol * input_volume

If vol is expressed as a decimal number followed by the string "dB", the value represents the requested change in decibels of the input audio power, and the output audio volume is given by the relation:

output_volume = 10^(vol/20) * input_volume

Otherwise vol is considered an expression and its evaluated value is used for computing the output audio volume according to the first relation.

Default value for vol is 1.0.