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.
- 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; deprecated, do not use
- 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.