heygen-com/hyperframes-audio

HyperFrames Audio

A mix is a set of relationships, not a stack of processors. Two tracks that each sound right alone can be unlistenable together, and the fix is almost never "turn one down" — it is finding what they are fighting over and giving it to whichever one needs it. Every tool here exists to express one of those relationships.

Effects live on the element as data-fx-chain, and preview and render run the same Web Audio graph — the studio in a live context, the engine in an offline one inside the browser it already drives. There is one implementation of each effect, so what you hear while scrubbing is what gets written. You never tune twice.

Clip timing remains /hyperframes-core: audio/video trims and source ranges use data-start, data-duration, and data-media-start, and crossfades overlap clips on different tracks. This skill owns placed-track fade-in/fade-out, crossfade envelopes, track gain/track volume, volume and effect automation, ducking/voiceover carve, and the effect chain. /media-use owns sourcing, generation, and preprocessing.

Constant data-playback-rate (0.1..5) is render-safe for picture and pitch-preserved sound when matching audio/video elements use the same timing, source offset, and rate. Source speed ramps are not supported because there is no rate envelope; preprocess a derived synchronized asset. HyperFrames does not provide automatic waveform sync or drift correction. For copyable cut/crossfade/retime recipes, use /hyperframes-core → references/creator-editing-recipes.md.

Three attributes carry everything, on the audio/video element itself — or, for the first two, on an <hf-audio-group> bus (see "One bus for many tracks"):

Attribute	Holds
data-fx-chain	the effects, in signal order
data-automation	envelopes on this track's volume or its effect parameters
data-fx-carve	the carve's own settings, so it can be re-derived

The shipped effect families are gain, EQ (highpass, lowpass, peaking, shelves), compressor, limiter, gate, saturate, delay, reverb, chorus, phaser, and bitcrush.

Exact JSON for each, and the rules a lane must satisfy: references/attributes.md. Every effect with its parameters, ranges and units: references/fx-registry.md. How to work out what is wrong with a file you cannot hear: references/diagnosis.md. Presets, named jobs and one-knob profiles, plus a symptom-to-fix table: references/presets.md — read that before hand-building a chain, because one of the presets or named jobs usually already names the problem.

How it fits together

Two authoring surfaces write those attributes; two runtimes read them through the same builders. That shared middle is why preview predicts the render.

flowchart TB
  voice["voice track<br/>media file"]
  bed["music bed<br/>media file"]

  subgraph AUTHOR["Authoring — the only things that write attributes"]
    panel["Studio<br/>Voiceover carve control"]
    script["scripts/carve.mjs<br/>detects the pair, dynamic by default"]
    analysis["core/audioCarve.ts<br/>carveProfile · analyseCarveBands<br/>analyseCarveDuck · analyseCarveDynamics"]
    panel --> analysis
    script --> analysis
  end

  voice --> analysis
  bed --> analysis

  subgraph ATTRS["Written onto the bed element"]
    carveAttr["data-fx-carve<br/>source · strength · dynamic"]
    chainAttr["data-fx-chain<br/>peaking xN + gain, tagged fromCarve"]
    autoAttr["data-automation<br/>a lane per carved parameter"]
  end

  analysis --> carveAttr
  analysis --> chainAttr
  analysis --> autoAttr

  subgraph SHARED["One implementation, read by both"]
    build["audioFxGraph.ts · buildFxChain"]
    sched["audioFxAutomation.ts · scheduleChainAutomation"]
  end

  chainAttr --> build
  autoAttr --> sched

  build --> preview["Preview<br/>live AudioContext<br/>attachElementFxChain"]
  sched --> preview
  build --> render["Render<br/>OfflineAudioContext in the headless browser<br/>applyAudioFxChain"]
  sched --> render

  preview --> heard["what you hear while scrubbing"]
  render --> wav["processed WAV<br/>+ chainTailSeconds so the mix lets the tail through"]
  wav --> mix["engine · audioMixer<br/>volume lane baked into the PCM here, not in the graph"]
  mix --> out["the rendered mix"]

  edit["editing the attribute mid-playback"] -.->|MutationObserver| preview

The carve's own settings are never read at playback — the chain and lanes it produced are what play. data-fx-carve exists so strength can be changed on an existing carve instead of guessed back out of the filters.

Inside a carved bed the signal runs through the dips first, then the level match, then anything you built yourself — which is why a limiter you add still acts as the last ceiling:

flowchart LR
  src["decoded bed"] --> p1["peaking<br/>400 Hz"]
  p1 --> p2["peaking<br/>1 kHz"]
  p2 --> p3["peaking<br/>1.6 kHz"]
  p3 --> g["gain<br/>level match"]
  g --> hand["your own effects<br/>e.g. limiter"]
  hand --> dest["track gain, then out"]

  l1["lane fx.n1.gain"] -.->|"envelope of the voice's<br/>level in that band"| p1
  l4["lane fx.n4.gain"] -.->|"how far the bed<br/>ducks overall"| g

A static carve is the same graph with fixed values and no lanes at all.

First, work out what is wrong

The table below starts from "it sounds boomy" — which presumes somebody already listened and said so. Handed a file and "fix this", you have no such sentence and you cannot listen, so you have to measure. One rule governs all of it:

The absolute spectrum of a single unknown voice cannot be diagnosed. Formants are ±10 dB, fundamentals run 85–255 Hz, and sentences decline 5–6 dB as they end. Every one of those reads as a defect on its own, and every one of them is the speaker.

So compare, and compare against something inside the same file: the clean original if it exists, otherwise the pauses — whatever is audible in a gap is additive, and the gap's spectrum is the channel rather than the voice. Comparing against a published average spectrum or a synthesised control voice does not work: two speakers differ by more than most defects, and both wrong answers in the evaluation behind this guidance came from exactly that.

When there is no original and no usable silence, a static tonal defect is genuinely under-determined. Say so and offer the readings that fit, rather than picking one and building a chain on it.

Commands, traps and worked recipes: references/diagnosis.md. Read it before diagnosing a file nobody has described.

Start from the symptom

Once you know the band and the kind, name what is wrong with the audio. Most bad audio is one or two of these, and each has a shipped answer:

It sounds like	Reach for
Hum or thump underneath	rumble-cut, or a highpass at 80 Hz
Boomy, chesty	Tame Boominess job (200 Hz)
Muffled, behind cardboard	Reduce Mud job (250 Hz)
Words hard to make out	Add Clarity job (3 kHz), or carve the bed
Harsh and tiring	Soften Harshness job (3.2 kHz)
Some words much louder than others	Evenness on a compressor, or Even Out Levels
Room tone between sentences	room-gate
Voice and music fighting	Voiceover carve — not an EQ on either
Dry, recorded nowhere	room-tight or room-natural
Just "amateur"	voice-clean, which is four of the above in order

Full catalogue, what each preset contains, the band vocabulary, and what is deliberately NOT covered (de-essing, noise removal, tone match): references/presets.md.

Subtract before you add, level after you filter, relationships after level, character and ceiling last. Each step changes what the next one hears — a compressor set before a high-pass spends its time chasing rumble.

Reach for a family by the problem, not the name

Filters (highpass, lowpass, peaking, lowshelf, highshelf) decide which frequencies a track is allowed to occupy. This is the first tool for two sources colliding, because collisions happen in bands: a bed and a voice both want 1–3 kHz, and taking that from the bed costs the bed far less than turning the whole thing down costs the mix. A high-pass on a voice is the standard fix for rumble; a low-pass darkens or muffles deliberately.

Dynamics (gain, compressor, limiter, gate) decide how a track's level behaves over time. Compression narrows the distance between loud and quiet so the quiet parts can come up. A limiter is a ceiling — it does not shape anything, it guarantees nothing gets past. A gate removes what is below a threshold, which is how you silence room tone between phrases. gain is a plain level stage, and it is what an automation lane rides when a track has to move out of the way.

Nonlinear (saturate, bitcrush) changes the waveform's shape, which adds harmonics that were not there. Reach for it when a track needs character or grit rather than correction — and remember it is generative: it makes a thin source denser, not cleaner.

Time (delay, reverb, chorus, phaser) puts a track in a space or gives it width. These are the ones that most easily wreck a mix, because a tail or a detuned copy occupies the same room a voice needs. Use them on the thing that should sit behind something else, and keep the wet amount lower than sounds right in isolation.

The chain is serial: each effect processes what the one before it produced. So corrective filtering goes early, character in the middle, and a limiter last where it can actually act as a ceiling.

Voiceover carve

The problem it solves. A music bed under a voice makes the voice hard to follow. The reflex is to duck the whole bed, which works and costs the bed all of its presence — the music goes limp for the entire voiceover. But the voice does not need the whole spectrum. It needs the few bands it actually occupies. Carve takes only those, and the bed keeps its low end and its top, so it is still music while the voice is still intelligible.

It is a relationship, not an effect. The settings live on the bed — the track that gets processed — and they name the voices to listen to, exactly as a sidechain compressor does: you select the track that gets quieter and pick what makes it quieter. Never put a carve on a voice track. A voice carved against itself is a bug, not a subtle mix choice.

Every voice, not one of them. sources is a list, because a bed usually runs under a whole sequence — a narrator, an interview answer, a second presenter. They are summed onto the bed's own clock before anything is measured (mixCarveSources), so one analysis covers all of them: the bands come from all the speech there is, and the envelopes rise wherever any of it is happening. Voices that never play while the bed does are left out; they cannot mask it.

A carve against more than one clip id is wrong. Group the clips and carve against the group. This is an invariant, not a tip. Naming clips one by one has to be exhaustively right and stays right only until the next edit — a fourth narration clip added later plays outside the carve's awareness, and the bed fails to duck under it silently. Naming the group instead resolves membership at analysis time, so a clip added to the group later is covered without touching sources at all:

<!-- group the narration, then carve the bed against the group -->
<audio id="vo-intro" data-audio-group="voiceover" …></audio>
<audio id="vo-middle" data-audio-group="voiceover" …></audio>
<audio id="vo-outro" data-audio-group="voiceover" …></audio>

<audio id="music" data-fx-carve='{"enabled":true,"sources":["voiceover"],"strength":0.8}' …></audio>

A sources list naming two or more plain clip ids instead of a group is caught by the audio_carve_ungrouped_sources lint rule — it still works, but it is the version that silently rots when a clip is added.

Keep the carve group a voice group: no bed, no SFX, no music. A group id in sources resolves to every current member on every analysis, so the group you name is the group you get later — not the tracks that were measured when it was written. Two ways that bites:

• The bed in its own source group. It is handed to itself as a voice and carved against its own content — the "never carve a track against itself" rule arriving one re-analysis later.
• An SFX or music clip in the voice group. It enters the sidechain on the next analysis and the bed starts ducking under a whoosh, even though the run that wrote the attribute never measured it.

Both are invisible at the moment the carve is written: the analysis sums the voices it detected and never round-trips through group resolution, so the first pass is genuinely correct and only the next one is wrong. So give each role its own group — music for the bed, voiceover for the narration, sfx for the hits — and keep the group named in sources holding nothing but voices.

carve.mjs refuses to write the group form when it sees either case, records clip ids, and says on stderr which member blocked it. The audio_carve_ungrouped_sources rule then points at the arrangement instead of the CLI quietly persisting a wider carve than it measured.

A voice that this run left out is not one of these cases and does not block the group form: carve.mjs only analyses voices that overlap the bed, and picking up a clip that plays later without an edit to sources is the whole reason to name the group.

One bus for many tracks

Membership alone is enough to carve against, as above — but add an <hf-audio-group> element with that id and the group becomes a real submix bus: one chain, one fader, one automation clock for every member.

<hf-audio-group
  id="voiceover"
  data-label="Voiceover"
  data-volume="0.9"
  data-fx-chain='{"version":1,"nodes":[
    {"type":"compressor","id":"g1","params":{"threshold":-18,"ratio":3}},
    {"type":"peaking","id":"g2","params":{"frequency":3000,"gain":2,"q":1}}]}'
></hf-audio-group>

<audio id="vo-intro" data-audio-group="voiceover" …></audio>
<audio id="vo-middle" data-audio-group="voiceover" …></audio>

Reach for the bus when the same treatment belongs on several tracks. Four narration clips that each want the same compressor is four chains to keep in step, and they drift the moment one is edited; on the bus it is one chain, and the compressor sees the whole voice rather than each clip in isolation — which is the point, since a compressor cannot ride a sequence it only hears a third of. Per-clip chains remain right for what is genuinely per-clip: one noisy take that needs its own de-esser.

On the bus	Does
data-fx-chain	one chain over the summed members
data-automation	envelopes on the bus, in COMPOSITION time
data-volume	one fader for every member (default 1)
data-label	the display name; falls back to the id
data-hidden	drops every member from the mix

Group automation is composition time, not clip time. A bus has no data-start — members are already at their composition positions when they reach it — so t: 0 in a group lane is the start of the composition, not of any clip. A lane on a clip is clip-local; the same numbers mean different instants on the two, which is the one thing to get right when moving an envelope from a clip up onto its bus.

A carve stays on the clip. data-fx-carve is not a group attribute. The bed being carved is a single track, and it is that track which carries data-fx-carve — pointed AT a group, per the rule above. Group and carve meet in sources, not on one element. A carve written onto a bus is half an effect applied twice: the level half measures the bed's own audio, which a bus has none of, so only the filters survive — and a bus and its members are one signal path, so the bed then runs through the bus's filters AND its own. The audio_group_carve_attr lint rule catches it.

One clip is not a bus. A group exists to give several tracks one chain, one fader and one clock. Wrapping a single clip in a bus buys nothing the clip's own data-fx-chain does not already do, and it doubles the places a later edit has to land. The one reason to do it anyway: a bus's automation clock is composition time, so a single-member bus is how a lane on that clip gets composition-time timing.

One knob. strength is 0..1 and derives everything: how deep to cut, how many bands, how wide, how far to favour intelligibility over raw voice energy, how far the level may drop, how far under the voice to aim. Those six move together in any real mix — a gentle carve is a shallow cut in few bands with little ducking, a hard one is deeper in more bands with more — so they are one relationship written once, in carveProfile. carve.mjs defaults to 0.8 — six bands from 250 Hz to 2.5 kHz cut about 7 dB each and 15 dB at 1.6 kHz, with 19 dB of level room — because a bed under narration has to get out of the way first and be music second; 0.25 (a 6 dB dip in three bands, 6 dB of room) kept the bed present but still let it fight the voice, and was judged too weak in practice. At 0.5 the dip reaches 10 dB, which is where a carve starts being heard as an effect rather than as room for the voice. Drop the strength when the bed is the point and the voice is sparse. 0 is spectral only — one band, no level match at all.

Carve by default — required whenever music plays under a voice. A bed under any voice track (narration, avatar speech, interview, voiceover) gets a carve as part of finishing the mix, not as a polish step to get to if there is time. Place both tracks, run the command below (default strength 0.8; add --bed / --voice when detection picks wrong), confirm the written data-fx-carve, data-fx-chain and data-automation with npx hyperframes check, and only then render. A volume duck on its own is not a finished mix: it leaves the voice and the bed fighting in the 1–3 kHz band and costs the bed all of its presence for the whole voiceover. Skip the carve only when there is no voice for the music to sit under — a music video, a title card, a montage cut to the track.

It always follows the voice. There is no static mode: a fixed depth thins the bed through every pause, and once you have heard both there is no reason to want it. Every value becomes an envelope of the speech's own level — silence leaves the bed alone, a loud passage pushe