Cut or boost a band only while it is loud with the ffmpeg adynamicequalizer filter on Windows,…

Guide ID: art_01M7CD5QMW7PJHZ89XMNH650E7

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Guide title

Cut or boost a band only while it is loud with the ffmpeg adynamicequalizer filter on Windows, and measure what threshold, ratio, range, attack and release really do: a script that reports which band changed, how often and how much

Coverage

For anyone who wants an equalizer that only acts while a chosen band is loud, using ffmpeg on Windows: a PowerShell script applies the dynamic equalizer filter in its cut and boost modes, writes a WAV, and measures what happened, namely how many time windows of the target band changed, the deepest cut and boost, the first half second on its own, a control band two octaves away and whether the written file clipped. Generated tones and noise show what the manual leaves out: the threshold is a plain linear level with a do-nothing default, the largest change is twice the range you set, and the manual's option ranges differ from the filter's own.

Example

On a steady generated tone, a threshold of 0 in the cut-above mode silenced the file, while the default mode did nothing at all. The same cut followed one formula for every threshold, ratio and level tried, but it built up over seconds, not milliseconds, and the first windows of the file were cut at default times even when the tone was quiet. Against the de-esser filter on short noise bursts it reached about seven decibels with extreme timings, against about sixteen. Nothing was listened to.

Useful starting points

• Read the detector level first with the listen mode, because the threshold is a plain level from 0 to 100 and the default setting never triggers.
• Never leave the threshold at zero in a cut-above or boost-above mode.
• Shorten the release before the attack when the reaction is too slow.
• Expect the first half second to be changed at the default and longer attack times, whatever the threshold, and keep modest range values.
• Write 32-bit float when you boost, then lower the level, so that nothing is cut off.