FFmpeg 4.4.5
Since* 0.9
#

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.

replaygain_noclip

Prevent clipping by limiting the gain applied.

Default value for replaygain_noclip is 1.

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.

#

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