Add an echo to a recording with the ffmpeg aecho filter on Windows, and check what it did: a…

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Guide title

Add an echo to a recording with the ffmpeg aecho filter on Windows, and check what it did: a script that predicts the time and level of every echo, probes the filter with an impulse, and flags clipping and the longer file

Coverage

Adding a delay-style echo to audio with a command line tool, and knowing where each repeat lands and how loud it is. A PowerShell script runs the ffmpeg aecho filter, writes a WAV or FLAC, then prints the expected level and time of every echo, the output length, the peak, and a probe that sends one click through the same filter to check the echoes. Generated tones and noise show what the four numbers do.

Example

On a generated click, the direct sound came out at the two gains multiplied and each echo at its own decay times the output gain, one copy per delay. The file ran as long as the longest delay longer than the input. A 1 ms delay removed one tone and kept others. Two copies adding past full scale were flattened by the filter itself. Nothing was listened to.

Useful starting points

• Run the plan first: it prints each echo's level before anything is written.
• Lower the output gain first when the peak line warns; lowering the decays also helps but changes the balance.
• Keep delays well above a few milliseconds if you want an echo, not a filter.