Adjust FFmpeg silencedetect Threshold and Duration
This article explains how to configure the silencedetect
filter in FFmpeg to identify silent periods in audio and video files.
You will learn how to adjust the two primary parameters of this filter:
the noise threshold, which defines what volume level constitutes
silence, and the duration, which sets the minimum length of time the
silence must last to be detected.
The silencedetect filter analyzes the audio stream of an
input file and outputs timestamps of detected silence to the console
log. To customize this detection, you need to modify the
noise (or n) and duration (or
d) options.
The Duration Parameter
The duration parameter specifies the minimum duration of
silence that must occur before FFmpeg flags it. If a silent period is
shorter than this value, it will be ignored.
- Option name:
durationord - Default value: 2 seconds
- Format: Can be expressed in seconds (e.g.,
3or0.5) or time duration syntax (e.g.,00:00:03).
The Noise Threshold Parameter
The noise parameter determines the maximum volume level
that is still considered silence. Any audio below this threshold is
treated as quiet enough to be flagged.
- Option name:
noiseorn - Default value: -91dB (decibels)
- Format: Can be expressed in decibels (e.g.,
-50dB) or as an amplitude ratio decimal (e.g.,0.001). Decibels are generally easier to use.
How to Use the Parameters in a Command
To apply these settings, pass them to the
-filter_complex or -af (audio filter) flag
using the format
silencedetect=noise=THRESHOLD:duration=DURATION.
Example 1: High Sensitivity (Short, Quiet Silence)
If you want to detect silence that lasts at least 0.5 seconds with a threshold of -50dB:
ffmpeg -i input.mp3 -af "silencedetect=noise=-50dB:duration=0.5" -f null -Example 2: Low Sensitivity (Longer, Louder Silence)
If you want to find silent gaps that are at least 5 seconds long, allowing for a higher ambient noise level of -30dB:
ffmpeg -i input.mp4 -af "silencedetect=n=-30dB:d=5" -f null -Reading the Output
When you run these commands, FFmpeg will output the results to the standard error stream. Look for lines in the output that resemble the following:
[silencedetect @ 0x7fa26bc040c0] silence_start: 12.45
[silencedetect @ 0x7fa26bc040c0] silence_end: 15.82 | silence_duration: 3.37This output indicates that silence started at 12.45 seconds and ended at 15.82 seconds, lasting for a total of 3.37 seconds.