71 lines
4.3 KiB
Markdown
71 lines
4.3 KiB
Markdown
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# Mixing in HyperFrames
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Preview and render run the same Web Audio graph, so what plays while scrubbing is what renders. Everything lives in attributes on the `<audio>` or `<video>` element.
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## Level and fades
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| Attribute | Meaning |
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| ------------------------------- | ----------------------------------------------------------------------------------------- |
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| `data-volume` | Track gain, 1 = 0 dB |
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| `data-fade-in`, `data-fade-out` | Edge fades in seconds |
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| `data-playback-rate` | Constant speed, 0.1–10, pitch preserved; give a video and its paired audio the same value |
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A crossfade is two clips on different tracks that overlap, each with a fade.
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## `data-automation`: envelopes
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```html
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<audio
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id="music"
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data-automation='{"version":1,"lanes":[{"target":"volume","points":[{"t":0,"v":1},{"t":2.5,"v":0.35}]}]}'
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…
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></audio>
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```
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- `target` is `volume`, `rate` (a speed ramp, 0.1–10, overrides `data-playback-rate`) or `fx.<nodeId>.<param>`.
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- `t` is seconds from the start of the clip, not of the composition. `v` is in the parameter's unit: 0..1 for volume, dB for a gain, Hz for a frequency.
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- A lane holds its first value back to the clip's start and its last value to its end, so a bed that starts before the voice needs an explicit full-level point at `t: 0`.
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- `curve` (-1..1) bends the segment leaving a point. 512 points per lane at most.
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- Don't also tween `volume` with GSAP on a track that has a volume lane or a `data-volume`; lint flags both.
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## `data-fx-chain`: effects
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```json
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{
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"version": 1,
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"nodes": [
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{ "type": "highpass", "id": "n1", "label": "Remove rumble", "params": { "frequency": 80 } },
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{
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"type": "peaking",
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"id": "n2",
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"label": "Clarity",
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"params": { "frequency": 3000, "gain": 2.5, "q": 1 }
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},
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{ "type": "limiter", "id": "n3", "params": { "limit": -1 } }
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]
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}
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```
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- Write the attribute double-quoted with the JSON's quotes as `"`.
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- Order is signal order. `id` is what automation targets (`fx.n2.gain`); give every node one, and a `label` when it does a named job. `enabled: false` bypasses a node.
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- Effects: `gain`, `highpass`, `lowpass`, `peaking`, `lowshelf`, `highshelf`, `compressor`, `limiter`, `gate`, `saturate`, `delay`, `reverb`, `chorus`, `phaser`, `bitcrush`.
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- `compressor`, `limiter`, `gate` and `bitcrush` can't be automated; a lane on them does nothing. Automate a `gain` before them instead.
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- Never set `fromCarve` by hand.
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- `reverb` and `delay` make the rendered track longer than its source; that is expected.
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| It sounds like | Reach for |
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| --------------------------- | ------------------------------------------- |
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| Hum, rumble, handling noise | `highpass` at 80 Hz |
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| Boomy, too close | `peaking` 200 Hz, −4 dB |
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| Muffled | `peaking` 250 Hz, −3 dB |
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| Words hard to make out | `peaking` 3 kHz, +2.5 dB, or duck the music |
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| Harsh | `peaking` 3.2 kHz, −3 dB |
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| Peaks clipping | `limiter` last in the chain |
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## Music under a voice
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Duck the bed with a `volume` lane on the music: full level before the voice, down to about 0.3–0.4 while anyone speaks (word timings from `npx hyperframes transcribe` or the voiceover give the times), back up after. Then carve the bed, which dips only the bands the voice uses: `node <SKILL_DIR>/audio/scripts/carve.mjs --comp index.html` (needs `ffmpeg` and `@hyperframes/core` in the project; `--dry-run` to see the plan). It is the same analysis as Studio's carve panel. It reads only double-quoted attributes (JSON quotes as `"`), so write the bed's chain and lanes that way or it overwrites them. Never put a carve on a voice track.
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## Group buses
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Give clips the same `data-audio-group="<id>"` to treat them as one group. An `<hf-audio-group id="<id>">` element with that id makes the group a submix bus with one `data-fx-chain`, one volume and one automation clock for every member. Keep one role per group: `voiceover`, `music`, `sfx`.
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