docs(skills): teach speed ramps as a rate lane in one reference page

docs/docs.json

@@ -902,7 +902,8 @@
             "pages": [
               "reference/html-schema",
               "reference/color-grading",
-              "reference/audio-effects"
+              "reference/audio-effects",
+              "reference/speed-ramps"
             ]
           },
           {

docs/reference/html-schema.mdx

@@ -124,7 +124,7 @@ Audio has no visual lifecycle.
 | Attribute | Applies to | Meaning |
 | --- | --- | --- |
 | `data-media-start` / `data-playback-start` | Video, audio, nested composition | Offset into the source file, used by trim and split. Two groups of readers disagree, so the right name depends on the element. **Read only `data-media-start`:** the timing compiler, the HTML parser, `hyperframes validate` (which only inspects `<audio>`), and the engine's audio mixer (which feeds ffmpeg `-ss`). **Read `data-playback-start` first, falling back to `data-media-start`:** the runtime player, Studio (which also writes it), and `hyperframes snapshot`. Because the audio mixer reads only `data-media-start`, a `<video>` authored with just `data-playback-start` renders a trimmed picture over untrimmed audio. Set the name by kind: **`<video>` / `<audio>` → `data-media-start`**; **nested composition → `data-playback-start`** — composition hosts are inspected only by the playback-start-first readers (the media-start-only ones are all `<video>`/`<audio>`-scoped). `data-media-start` still works there as a fallback, but `data-playback-start` is the canonical name Studio writes and normalises to for new composition hosts, so the other name works until an edit rewrites it (it is the [child-timeline offset](/concepts/compositions)). |
-| `data-playback-rate` | Video, audio, nested composition | Playback multiplier from `0.1` to `5` |
+| `data-playback-rate` | Video, audio, nested composition | Playback multiplier from `0.1` to `10`. A `rate` lane in `data-automation` overrides it; see [Speed ramps](/reference/speed-ramps) |
 | `data-volume` | Video and audio | Static gain. `1` is 0 dB, `0` is silence, and values above `1` boost up to `3.98` (+12 dB) |
 | `data-has-audio="true"` | Video | Declares that the video contributes audio |
 

docs/reference/speed-ramps.mdx

@@ -0,0 +1,66 @@
+---
+title: "Speed ramps"
+sidebarTitle: "Speed ramps"
+description: "Change a clip's playback speed over time with a rate lane in data-automation. One curve drives the preview, the render and Studio."
+---
+
+A speed ramp changes how fast a `<video>` or `<audio>` clip plays while it
+plays: slow into a beat, fast out of it. It is a `rate` lane in
+[`data-automation`](/reference/audio-effects#the-four-attributes), the same
+attribute that carries volume envelopes.
+
+```html
+<video
+  src="clip.mp4"
+  data-start="0"
+  data-duration="4"
+  data-track-index="0"
+  data-automation='{"version":1,"lanes":[{"target":"rate","points":[{"t":0,"v":1},{"t":2,"v":4},{"t":4,"v":0.5}]}]}'
+></video>
+```
+
+## The lane
+
+| Field | Meaning |
+| --- | --- |
+| `target` | `"rate"` |
+| `points[].t` | Seconds from the start of the clip, not from the start of the composition |
+| `points[].v` | Speed multiplier. `1` is normal, `2` is twice as fast. Clamped to `0.1` to `10` |
+| `points[].curve` | Optional, `-1` to `1`. Bends the segment leaving this point |
+
+Speed moves between points on a logarithmic scale, so going from `0.5` to `2`
+passes through `1` at the midpoint. A lane wins over the constant
+`data-playback-rate` on the same element. Without a lane, the constant applies.
+
+## What stays the same everywhere
+
+The source frame shown at each moment comes from one function, `sourceTimeAt`,
+which the preview and the renderer both use, so the render shows the frames the
+preview showed. Set `data-duration` on the clip to fix how long it holds the
+timeline; without it the length follows from the source and the speed.
+
+Pitch is kept. The preview leaves the browser's default pitch correction on.
+The render time-stretches audio in short constant-speed slices of a quarter
+second, which approximates the curve while keeping pitch, so the sound follows
+the ramp closely rather than exactly.
+
+## Presets
+
+Studio's **Speed preset** menu draws a ready curve over the clip: Montage,
+Hero, Bullet, Jump cut, Flash in and Flash out. An agent can write the same
+points by hand.
+
+## Editing in Studio
+
+Select a clip and open its Media section. The **Speed** slider sets the
+constant rate. The **A** toggle next to it automates speed, which shows a rate
+lane on the clip in the timeline that you edit like the volume lane.
+
+## Limits
+
+- Only `<video>` and `<audio>` clips carry a rate lane.
+- Speeds outside `0.1` to `10` are clamped.
+- The viewer's own transport speed is a separate control that multiplies with
+  the clip's speed, and it is narrower: the Studio speed menu offers `0.25` to
+  `2`, the player's menu offers up to `4`, and the runtime clamps a transport
+  request to `0.1` to `5`.

skills-manifest.json

@@ -18,31 +18,31 @@
       "files": 4
     },
     "hyperframes": {
-      "hash": "05525e9c53582e4b",
+      "hash": "ca51ed2be534305c",
       "files": 26
     },
     "hyperframes-animation": {
       "hash": "479c716293a26531",
       "files": 122
     },
     "hyperframes-audio": {
-      "hash": "b39bac771e873eae",
+      "hash": "7e9a13aba7143c08",
       "files": 7
     },
     "hyperframes-cli": {
       "hash": "986414090bf6442f",
       "files": 11
     },
     "hyperframes-core": {
-      "hash": "77ce4deba31148a2",
+      "hash": "dae513efe1b0e803",
       "files": 11
     },
     "hyperframes-creative": {
       "hash": "0803c90800fda4ce",
       "files": 79
     },
     "hyperframes-keyframes": {
-      "hash": "6bc62531ecea9a52",
+      "hash": "16a7da9819e7e4ab",
       "files": 3
     },
     "hyperframes-registry": {

skills/hyperframes-audio/SKILL.md

@@ -32,10 +32,11 @@ 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
+Constant `data-playback-rate` (`0.1..10`) 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
+source offset, and rate. A speed ramp is a `rate` lane in `data-automation`
+(see `docs/reference/speed-ramps`); it wins over the constant and keeps pitch
+in preview and render. HyperFrames does not
 provide automatic waveform sync or drift correction.
 For copyable cut/crossfade/retime recipes, use `/hyperframes-core` → `references/creator-editing-recipes.md`.
 

skills/hyperframes-core/references/creator-editing-recipes.md

@@ -229,7 +229,7 @@ Timeline math: the still owns its hold duration. Source math: final-source frame
 ></video>
 ```
 
-Timeline math: duration is authored timeline time. Source math: consumed source = timeline duration × rate; natural timeline duration = remaining source / rate. Audio follows: matching separate audio track uses the same constant rate. Owner: `/hyperframes-core`. Limit: normalized 0.1..5 constant only; no speed ramp envelope.
+Timeline math: duration is authored timeline time. Source math: consumed source = timeline duration × rate; natural timeline duration = remaining source / rate. Audio follows: matching separate audio track uses the same constant rate. Owner: `/hyperframes-core`. Limit: normalized 0.1..10. For a speed ramp put a `rate` lane in `data-automation`, e.g. `{"version":1,"lanes":[{"target":"rate","points":[{"t":0,"v":1},{"t":2,"v":4}]}]}`; it wins over the constant.
 
 ## Zoom / punch
 

skills/hyperframes-keyframes/SKILL.md

@@ -34,8 +34,8 @@ fades use `/hyperframes-audio`.
 | Crop and mask reframe                   | Interpolate `clip-path` or a mask on an inner visual wrapper to crop/reframe without changing source time. Polygon keyframes can form a polygon/mask transition.                                                            |
 | Directional wipe cut or iris/reveal cut | Animate a mask/clip boundary across overlapping visual clips; `/hyperframes-animation` owns the handoff choreography.                                                                                                       |
 | Split-screen handoff                    | Keep both visual clips placed by core, then keyframe their inner crop/mask wrappers and divider geometry.                                                                                                                   |
-| Constant source retime                  | `/hyperframes-core` owns normalized `data-playback-rate` (`0.1..5`) for render-safe picture and pitch-preserved sound. It is constant for the whole media element.                                                          |
-| Source speed ramps                      | Not supported: there is no time-varying playback-rate envelope. Preprocess a derived media asset, then place it through core.                                                                                               |
+| Constant source retime                  | `/hyperframes-core` owns normalized `data-playback-rate` (`0.1..10`) for render-safe picture and pitch-preserved sound. It is constant for the whole media element.                                                         |
+| Source speed ramps                      | A `rate` lane in `data-automation` on the `<video>`/`<audio>` (`t` in clip seconds, `v` 0.1..10, log interpolation); it wins over the constant rate.                                                                        |
 | Freeze / hold                           | A visual pose, final source frame, or finished sub-composition can hold. Arbitrary mid-source freeze is not supported; preprocess a still/derived segment, place it as its own clip, then resume with another source range. |
 
 When editing picture and sound together, load `/hyperframes-core`, this skill for

skills/hyperframes/SKILL.md

@@ -108,10 +108,10 @@ Creator edit phrases are cross-domain requests. Load every skill named in the ma
 | fade, crossfade, track gain/volume, automation, duck/carve, audio effects, or one effect across several tracks     | `/general-video` + `/hyperframes-core` + `/hyperframes-audio`; core places clips, audio mixes placed tracks — including a submix bus over a group of them.                        |
 | picture and sound edits that combine cuts with camera motion or mixing                                             | `/general-video` + `/hyperframes-core` + `/hyperframes-keyframes` when there is visual motion + `/hyperframes-audio` when sound is faded, mixed, ducked, automated, or processed. |
 | lay out a project so it reads well in Studio: caption track, tracks per element kind, sub-compositions, safe zones | `/hyperframes-studio` + `/hyperframes-core`; studio owns the layout conventions, core owns each edit.                                                                             |
-| source or generate media, or preprocess an unsupported speed ramp/mid-source freeze                                | `/media-use`; sourcing/generation/preprocessing only, never placed-track mixing.                                                                                                  |
+| source or generate media, or preprocess an unsupported mid-source freeze                                           | `/media-use`; sourcing/generation/preprocessing only, never placed-track mixing.                                                                                                  |
 
 Constant `data-playback-rate` is render-safe for picture and pitch-preserved
-sound. It does not make source speed ramps keyframeable; preprocess ramps.
+sound. Speed ramps are a `rate` lane in `data-automation`.
 For copyable edit contracts, load `/hyperframes-core` → `references/creator-editing-recipes.md`.
 
 Broad feedback about how photographic media looks or behaves also routes to