volume

Adjust the input audio volume.

It accepts the following parameters:

'volume'

Set audio volume expression.

Output values are clipped to the maximum value.

The output audio volume is given by the relation:

output_volume = volume * input_volume

The default value for volume is "1.0".

'precision'

This parameter represents the mathematical precision.

It determines which input sample formats will be allowed, which affects the precision of the volume scaling.

'fixed'

8-bit fixed-point; this limits input sample format to U8, S16, and S32.

'float'

32-bit floating-point; this limits input sample format to FLT. (default)

'double'

64-bit floating-point; this limits input sample format to DBL.

'replaygain'

Choose the behaviour on encountering ReplayGain side data in input frames.

'drop'

Remove ReplayGain side data, ignoring its contents (the default).

'ignore'

Ignore ReplayGain side data, but leave it in the frame.

'track'

Prefer the track gain, if present.

'album'

Prefer the album gain, if present.

'replaygain_preamp'

Pre-amplification gain in dB to apply to the selected replaygain gain.

Default value for replaygain_preamp is 0.0.

'eval'

Set when the volume expression is evaluated.

It accepts the following values:

'once'

only evaluate expression once during the filter initialization, or when the 'volume' command is sent

'frame'

evaluate expression for each incoming frame

Default value is 'once'.

The volume expression can contain the following parameters.

'n'

frame number (starting at zero)

'nb_channels'

number of channels

'nb_consumed_samples'

number of samples consumed by the filter

'nb_samples'

number of samples in the current frame

'pos'

original frame position in the file

'pts'

frame PTS

'sample_rate'

sample rate

'startpts'

PTS at start of stream

'startt'

time at start of stream

't'

frame time

'tb'

timestamp timebase

'volume'

last set volume value

Note that when 'eval' is set to 'once' only the sample_rate and tb variables are available, all other variables will evaluate to NAN.

Commands

This filter supports the following commands:

'volume'

Modify the volume expression. The command accepts the same syntax of the corresponding option.

If the specified expression is not valid, it is kept at its current value.

'replaygain_noclip'

Prevent clipping by limiting the gain applied.

Default value for replaygain_noclip is 1.

Command line examples

• Halve the input audio volume:

  volume=volume=0.5
  volume=volume=1/2
  volume=volume=-6.0206dB
  

  In all the above example the named key for 'volume' can be omitted, for example like in:

  volume=0.5
  

• Increase input audio power by 6 decibels using fixed-point precision:

  volume=volume=6dB:precision=fixed
  

• Fade volume after time 10 with an annihilation period of 5 seconds:

  volume='if(lt(t,10),1,max(1-(t-10)/5,0))':eval=frame