# Ffmpeg Audio Fx > Creative and restoration audio effects with ffmpeg: chorus, flanger, aphaser, tremolo, vibrato, aecho, crystalizer, adecorrelate, adeclick, adeclip, apsyclip, asoftclip, speechnorm, dialoguenhance, adynamicequalizer, adynamicsmooth, afreqshift, aphaseshift, asupercut, asuperpass, asuperstop, atilt, afftfilt, bandpass, bandreject, biquad, allpass, ladspa, lv2. Use when the user asks to add echo/chorus/flanger, create psychedelic audio effects, enhance dialogue, de-click vinyl rips, soft-clip audio, apply LADSPA or LV2 plugins, or shift frequency. - Skill: `damionrashford/ffmpeg-audio-fx` (Agent Skill, multi-file: 3 files) - Install (CLI): `npx skillmds@latest add damionrashford/ffmpeg-audio-fx` - Raw SKILL.md: https://api.skillmd.com/api/skills/damionrashford/ffmpeg-audio-fx/raw - Safety review: pending - Works with: Claude Code, Claude.ai, OpenAI Codex - Category: Coding & Dev Tools - Author: damionrashford (https://skillmd.com/u/damionrashford) - Updated: 2026-09-17 - Page: https://skillmd.com/skills/damionrashford/ffmpeg-audio-fx --- # ffmpeg Audio FX **Context:** $ARGUMENTS Creative and restoration audio effects. `-af` chain syntax. Every recipe below is verified against the FFmpeg filters doc. For basic gain / EQ / loudnorm / tempo see the sibling `ffmpeg-audio-filter` skill — this one is modulation, delay, restoration, true-peak limiting, dynamic EQ, spectral domain, and plugin hosts. ## Quick start - **Add echo** — Step 2 (Delay group), recipe `aecho`. - **Chorus / flanger / phaser / tremolo / vibrato** — Step 2 (Modulation group). - **Normalize speech for a podcast** — Step 2 (Dynamics group), recipe `speechnorm`. - **Rescue vinyl rip** — Step 2 (Restoration group), chain `adeclick` → `adeclip`. - **Broadcast-safe true-peak limit** — `apsyclip` (Dynamics group). - **Host a LADSPA or LV2 plugin** — Step 2 (Plugin group). - **Shift frequencies (not pitch)** — `afreqshift` (Filter-curve group). ## When to use - Music production: add modulation (chorus/flanger/phaser), widen a mono source, add shimmer (crystalizer), analog-warm limiting (asoftclip). - Post / dialogue: enhance voice in a 5.1 mix (dialoguenhance), level an uneven interview (speechnorm), duck resonant frequencies (adynamicequalizer). - Restoration: vinyl / shellac / cassette rips (adeclick + adeclip + asupercut rumble filter), decorrelate stereo (adecorrelate). - Broadcast / streaming: psychoacoustic true-peak limiter (apsyclip) as the final stage before dithering to s16. - DSP / research: arbitrary biquads, spectral-domain manipulation (afftfilt), host third-party plugins via LADSPA / LV2. ## Step 1 — Classify the effect Group the request into one of five buckets before picking a filter: | Group | Filters | Use when | |---|---|---| | **Modulation** | `chorus`, `flanger`, `aphaser`, `tremolo`, `vibrato` | Add movement / wobble / thickness. | | **Delay** | `aecho` | Echo / slap-back / doubler. | | **Dynamics** | `speechnorm`, `dialoguenhance`, `adynamicequalizer`, `adynamicsmooth`, `asoftclip`, `apsyclip`, `crystalizer` | Level, duck, saturate, limit, sharpen transients. | | **Restoration** | `adeclick`, `adeclip`, `adecorrelate`, `asupercut` | Vinyl pops, clipped peaks, stereo smear, subsonic rumble. | | **Filter-curve / spectral** | `bandpass`, `bandreject`, `biquad`, `allpass`, `asuperpass`, `asuperstop`, `atilt`, `afreqshift`, `aphaseshift`, `afftfilt` | Surgical EQ, high-order filters, frequency shifting (not pitch), arbitrary spectral math. | | **Plugin host** | `ladspa`, `lv2` | Load an external DSP plugin. Requires build flags. | ## Step 2 — Build the filter chain Copy the exact recipe. Parameters that look arbitrary (e.g. `0.8:0.9:1000:0.3`) are positional and mismatched counts produce cryptic errors. ### Modulation ```bash # Echo (doubler / slap-back) — delays are MILLISECONDS ffmpeg -i in.wav -af "aecho=0.8:0.9:1000:0.3" out.wav # Chorus (6 positional args: in-gain:out-gain:delays-ms:decays:speeds:depths) ffmpeg -i in.wav -af "chorus=0.7:0.9:55:0.4:0.25:2" out.wav # Flanger (jet-swoosh; depth is ms range of the LFO) ffmpeg -i in.wav -af "flanger=delay=5:depth=2:speed=0.5" out.wav # Phaser (type=t triangle, s sine, n analog noise) ffmpeg -i in.wav -af "aphaser=type=t:speed=2" out.wav # Tremolo (volume modulation) ffmpeg -i in.wav -af "tremolo=f=5:d=0.5" out.wav # Vibrato (pitch modulation via delay) ffmpeg -i in.wav -af "vibrato=f=7:d=0.5" out.wav ``` ### Dynamics ```bash # Intelligent speech leveler — better than dynaudnorm for voice-only ffmpeg -i podcast.wav -af "speechnorm=e=12.5:r=0.0001:l=1" out.wav # Dialogue enhance (boosts the center channel voice band, REQUIRES 5.1+) ffmpeg -i film.wav -af "dialoguenhance" out.wav # Dynamic EQ — duck resonant 1 kHz band by 5 dB when it gets loud ffmpeg -i in.wav -af "adynamicequalizer=bandwidth=300:dfrequency=1000:direction=below:mode=cut:makeup=5" out.wav # Crystalizer (add harmonics / transient sharpening) — intensity > 3 = artificial ffmpeg -i in.wav -af "crystalizer=i=2" out.wav # Soft-clip (warm limiter; type= hard / tanh / atan / cubic / exp / alg / quintic / sin / erf) ffmpeg -i in.wav -af "asoftclip=type=tanh" out.wav # Psychoacoustic true-peak limiter (THE recommended broadcast limiter) ffmpeg -i in.wav -af "apsyclip=level_in=1:level_out=1:clip=0.9" out.wav ``` ### Restoration ```bash # Vinyl de-click (arorder 6-8 for vinyl; method a=autoregressive) ffmpeg -i vinyl.wav -af "adeclick=window=55:overlap=75:arorder=8:threshold=2:burst=2" out.wav # De-clip (threshold 10+ for obvious clipping; hsize=1000 history size) ffmpeg -i clipped.wav -af "adeclip=window=55:overlap=75:arorder=8:threshold=10:hsize=1000:method=a" out.wav # Subsonic rumble kill (sharp 20 Hz high-pass, 20th order Butterworth) ffmpeg -i in.wav -af "asupercut=cutoff=20:order=20" out.wav # Stereo decorrelation (adds a tiny inter-channel delay) ffmpeg -i mono_ish.wav -af "adecorrelate" out.wav ``` ### Filter-curve / spectral ```bash # Band-pass for voice intelligibility (Q=2 around 1 kHz) ffmpeg -i in.wav -af "bandpass=f=1000:width_type=q:w=2" out.wav # Frequency shift 50 Hz (NOT pitch shift — inharmonic, metallic) ffmpeg -i in.wav -af "afreqshift=shift=50" out.wav # Spectral tilt (lean EQ, +/- dB per octave) ffmpeg -i in.wav -af "atilt=freq=1000:slope=-3" out.wav # Arbitrary biquad IIR (coefficients b0,b1,b2,a0,a1,a2) ffmpeg -i in.wav -af "biquad=b0=0.5:b1=0:b2=0.5:a0=1:a1=0:a2=0" out.wav # FFT filter — real/imag expressions in spectral domain (null example) ffmpeg -i in.wav -af "afftfilt=real='hypot(re,im)*sin(0)':imag='hypot(re,im)*cos(0)'" out.wav ``` ### Plugin host ```bash # LADSPA: file=libname (no .so), plugin=label, c=key=val,... ffmpeg -i in.wav -af "ladspa=file=cmt:plugin=amp_stereo:c=gain=10" out.wav # LV2: p=plugin URI, c=key=val,... ffmpeg -i in.wav -af "lv2=p=http://calf.sourceforge.net/plugins/Reverb" out.wav ``` ## Step 3 — Run Encode to the target codec in the same invocation: ```bash ffmpeg -i in.wav -af "speechnorm=e=12.5:r=0.0001:l=1,apsyclip=clip=0.95" \ -c:a libopus -b:a 96k out.opus ``` For video input, pass the video through untouched with `-c:v copy`: ```bash ffmpeg -i in.mp4 -af "dialoguenhance,speechnorm=e=6.25" \ -c:v copy -c:a aac -b:a 192k out.mp4 ``` ## Step 4 — A/B verify Always listen to the result against the source. Use the `ffmpeg-playback` skill's `ffplay` recipes or diff loudness: ```bash ffmpeg -i in.wav -af "ebur128=peak=true" -f null - 2>&1 | tail -20 ffmpeg -i out.wav -af "ebur128=peak=true" -f null - 2>&1 | tail -20 ``` Target: integrated loudness inside spec (podcast -16 LUFS, streaming -14 LUFS, broadcast -23 LUFS), true peak ≤ -1 dBTP. ## Available scripts - **`scripts/afx.py`** — stdlib argparse front-end with subcommands for every recipe above. `--dry-run` prints the ffmpeg command without running it. `--verbose` shows the full argv. ```bash uv run ${CLAUDE_SKILL_DIR}/scripts/afx.py echo --input in.wav --output out.wav --delay-ms 600 --decay 0.4 uv run ${CLAUDE_SKILL_DIR}/scripts/afx.py deckick --input vinyl.wav --output clean.wav uv run ${CLAUDE_SKILL_DIR}/scripts/afx.py limit --input master.wav --output final.wav --method psy ``` ## Reference docs Read [`references/filters.md`](references/filters.md) for per-filter option tables, effect-type taxonomy, LADSPA/LV2 plugin discovery, and production recipe book (vinyl chain, voice chain, radio master chain). ## Gotchas - `aecho` delays are **milliseconds** in a pipe-separated string: `"1000|1500|2000"` means three echoes at 1 s / 1.5 s / 2 s. Decays list must match the delay count. - `chorus` positional args are `in-gain:out-gain:delays-ms:decays:speeds:depths`. Mismatched list counts produce a silent error / empty output. - `flanger` `depth` is the LFO oscillation range in **milliseconds** — typical 0.5–10. Higher sounds like pitch-bend seasickness. - `aphaser` `type=t` triangle LFO, `s` sine, `n` analog noise — noise sounds vintage / broken. - `tremolo` modulates **volume**, `vibrato` modulates **pitch** (via delay). They are easy to confuse; pick the one that matches what "tremolo" means on your instrument. - `adeclick` `arorder` should be 6–8 for vinyl; higher = more CPU and diminishing returns. `threshold` 2 is a good starting point. - `adeclip` needs `threshold=10` or more for obviously clipped material. Lower thresholds miss hard clips entirely. - `crystalizer` intensity > 3 gets fatiguing fast. Most mastering uses `i=1` to `i=2`. - `apsyclip` is **the** recommended true-peak limiter for broadcast — psychoacoustic masking hides artifacts better than plain `alimiter`. Set `clip=0.9` (about -0.9 dBTP) to stay under -1 dBTP. - `speechnorm` is better than `dynaudnorm` for voice-only material (podcasts, audiobooks). For music or mixed content use `loudnorm` instead. - `dialoguenhance` operates on stereo per current docs, but the real-world gain is on 5.1/7.1 where it targets the center channel. On stereo it will run but the effect is subtle. - `adynamicequalizer` supports both `mode=cut` (duck a resonance) and `mode=boost` (lift under a threshold). `direction=below` or `above` chooses whether it acts on quiet or loud material. - `biquad` is the generic bottom-level IIR. Prefer `highpass`, `lowpass`, `bandpass`, `allpass`, `equalizer`, `treble`, `bass` unless you genuinely need raw coefficients. - `afftfilt` takes two expressions (`real` and `imag`) — advanced spectral domain. `re`, `im`, `bin_h`, `mag`, `pha` are available symbols. - `afreqshift` is frequency shift (single-sideband), not pitch shift. It destroys harmonic relationships. For pitch shift use `rubberband` or `asetrate+atempo`. - `asupercut` / `asuperpass` / `asuperstop` are high-order Butterworth (up to 20th order) — use when a regular `highpass`/`bandpass` rolloff isn't steep enough. - `atilt` is linear-slope spectral tilt in dB/octave. Useful for pink-noise-style mastering adjustments. - LADSPA requires ffmpeg built with `--enable-ladspa`. Plugin `.so` files live in `/usr/lib/ladspa` (or set `LADSPA_PATH`). Invoke with `file=cmt` (not `file=cmt.so`) and `plugin=