Voice Activity Detector. Attempts to trim silence and quiet
background sounds from the ends of (fairly high resolution i.e.
16-bit, 44-48kHz) recordings of speech. The algorithm currently
uses a simple cepstral power measurement to detect voice, so may
be fooled by other things, especially music. The effect can
trim only from the front of the audio, so in order to trim from
the back, the reverse effect must also be used. E.g.
to trim from the front,
to trim from the back, and
| | norm vad reverse vad reverse
|
to trim from both ends. The use of the norm effect is recommended, but
remember that neither reverse nor norm is suitable
for use with streamed audio.
Options: Default values are shown in parenthesis.
-t num (7)-
The measurement level used to trigger activity detection.
This might need to be changed depending on the noise
level, signal level and other charactistics of the input
audio.
-T num (0.25)-
The time constant (in seconds) used to help ignore short
bursts of sound.
-s num (1)-
The amount of audio (in seconds) to search for quieter/shorter bursts
of audio to include prior to the detected trigger point.
-g num (0.25)-
Allowed gap (in seconds) between quieter/shorter bursts
of audio to include prior to the detected trigger point.
-p num (0)-
The amount of audio (in seconds) to preserve before the
trigger point and any found quieter/shorter bursts.
Advanced Options: These allow fine tuning of the algorithm's
internal parameters.
-b num-
The algorithm (internally) uses adaptive noise estimation/reduction
in order to detect the start of the wanted audio. This option sets
the time for the initial noise estimate.
-N num-
Time constant used by the adaptive noise estimator for
when the noise level is increasing.
-n num-
Time constant used by the adaptive noise estimator for
when the noise level is decreasing.
-r num-
Amount of noise reduction to use in the detection algorithm
(e.g. 0, 0.5, ...).
-f num-
Frequency of the algorithm's processing/measurements.
-m num-
Measurement duration; by default, twice the measurement
period; i.e. with overlap.
-M num-
Time constant used to smooth spectral measurements.
-h num-
"Brick-wall" frequency of high-pass filter applied at the
input to the detector algorithm.
-l num-
"Brick-wall" frequency of low-pass filter applied at the
input to the detector algorithm.
-H num-
"Brick-wall" frequency of high-pass lifter used in the
detector algorithm.
-L num-
"Brick-wall" frequency of low-pass lifter used in the
detector algorithm.
See also the silence effect.