Silence Detect

Detect silent spans in an audio or video track and emit them as source-clock ranges.

Overview

The Silence Detect node runs one local FFmpeg silencedetect pass over the connected audio or video and returns the silent spans as a structured JSON payload on its json output handle. It never calls an external provider, so it works on a keyless (community) install.

It reads a cheap 16 kHz mono audio proxy of the source, so a long recording is analysed in seconds rather than by downloading and decoding the full-resolution original. Connect an audio track or a video (its audio is used automatically) and run.

The output is data, not media — feed it into data/JSON consumers (for example, an editing/EDL step or an Extract Field node), not a media input.

Inputs & Outputs

Inputs: Audio or Video (required)

Outputs:

• json — a SilenceDetect result object:

{
  "version": 1,
  "ranges": [
    { "startMs": 2120, "endMs": 3880 }
  ],
  "durationMs": 6000
}

• ranges — the silent spans, in milliseconds on the source clock, ordered as they occur. endMs is exclusive and always greater than startMs.
• durationMs — the total source duration, in milliseconds.

Configuration

Field	Default	Description
Silence threshold (thresholdDb)	-35	Audio quieter than this (in dBFS, always ≤ 0) counts as silence. A lower value is stricter (only near-total quiet is silence).
Minimum silence (minSilenceMs)	700	Only gaps at least this long (in ms) are reported.
Speech padding (padMs)	120	Padding kept around speech (in ms). Each detected span is shrunk inward by this amount at both ends so a downstream cut doesn’t clip a breath or the attack of a word. A span that would collapse to nothing after padding is dropped.

Credits

Flat 1 credit per run, regardless of source length, threshold, or the number of ranges found. The pass is a local FFmpeg analysis with no external provider cost.

Worked example

A 6-second recording that is silent between the 2- and 4-second marks, run with the defaults (thresholdDb: -35, minSilenceMs: 700, padMs: 120):

1. silencedetect reports one silent span from ≈ 2.000 s to ≈ 4.000 s (a 2-second gap, comfortably above the 700 ms minimum).
2. The 120 ms speech padding shrinks the span inward at both ends: start 2000 + 120 = 2120 ms, end 4000 − 120 = 3880 ms.

Result:

{
  "version": 1,
  "ranges": [
    { "startMs": 2120, "endMs": 3880 }
  ],
  "durationMs": 6000
}

Cost: 1 credit.

Best Practices

• Raise Minimum silence to ignore short breaths and inter-word gaps; lower it to catch brief pauses.
• If cuts are clipping the start of words, increase Speech padding; if silences feel too generous, decrease it.
• A very quiet room tone may sit above the default threshold — lower Silence threshold (e.g. to -45) to treat quiet ambience as silence.
• The ranges are on the source clock, so they line up with the original audio/video timeline for a downstream edit.

Common Use Cases

• Find dead air and long pauses in a podcast or interview before an editing pass.
• Feed the ranges into a downstream tighten/edit step that removes silence.
• Measure how much of a recording is silence versus speech.