Build a compressor or limiter from the ffmpeg compand curve on Windows and measure what it…

Guide ID: art_01M7CD1J0187CXXHB845FXK4WF

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Guide title

Build a compressor or limiter from the ffmpeg compand curve on Windows and measure what it really does: a script that prints the true input-to-output level table, the attack lag, the delay look-ahead and the point-list rules

Coverage

Making a compressor or a limiter from ffmpeg's single compand filter and checking it with numbers. A PowerShell script builds the transfer curve from a threshold and ratio, a ceiling, or your own point list, writes a WAV or FLAC, and prints the real input-to-output level table next to what the points promise. Generated tones show where the filter departs from its manual: its own defaults, the lag of the level tracker, the start-up level, the look-ahead delay and the point-list rules. Gates and expanders are left to other records.

Example

On generated tones, a bare compand lifted a quiet tone by tens of dB, an attack above zero made the output louder than the points said, a limiter with a short attack let a loud burst through at full level, and a list ending below zero dB behaved differently from one ending above it. Nothing was listened to.

Useful starting points

• Print the plan with the curve table first and read the measured column before trusting the points.
• Use an attack of zero when the points must hold, and a decay above zero in a limiter.
• End a point list with a point above zero dB.
• Write a 32-bit float file when the result may go above full scale.