Update README for the video viewer

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

README.md

@@ -13,30 +13,21 @@ short_description: Frame-locked viewer for rollouts vs. ground truth
 
 # Rollout vs. ground truth
 
-Side-by-side viewer for forward-dynamics world-model rollouts. Type a **dataset repo id** into
-the box at the top and it renders that repo — the Space holds no data of its own and is not tied
-to any one dataset.
+Side-by-side viewer for forward-dynamics world-model rollouts. The page starts empty and assumes
+no dataset — type a **dataset repo id** into the box, press **Load**, and pick an episode.
 
-Accepted forms: `owner/name`, `owner/name@revision`, or a pasted `https://huggingface.co/datasets/…`
-URL. `DATASET_REPO` sets what is prefilled at startup.
+Accepted forms: `owner/name`, `owner/name@revision`, or a pasted
+`https://huggingface.co/datasets/…` URL.
 
 ## What it shows
 
-- **Playback** — GT and generated rendered into one video, so the two panels stay frame-locked
-  instead of drifting apart the way two independent players do. Optional `|GT − generated|`
-  difference panel. Playback fps is adjustable (a 33-frame window is only ~1 s at 30 fps).
-- **Frame stepper** — a single frame from both videos side by side, defaulting to the critical
-  frame when the dataset marks one.
-- **Driving actions** — the action chunk fed to the model. A 14-D chunk is split into grippers /
-  left-arm / right-arm; any other width is plotted as raw channels.
-- **Rerun** — the same window in a [Rerun](https://rerun.io) viewer: every camera and every
-  action channel on one shared frame timeline, so scrubbing moves all of them together. One row
-  per camera (GT | generated | optional diff) over a time-series plot of the actions, with the
-  critical frame marked. Built only when you open the tab, and only for the cameras selected.
-- **All windows** — sortable table of every window; click a row to load it.
-
-Filter by task, gripper edge and arm; sort by critical-frame PSNR to jump to the hardest or
-easiest cases.
+Ground truth and the generated rollout are composed into a **single video**, so the two panels
+stay frame-locked; two independent players drift apart and cannot be scrubbed together. The strip
+carries in-frame captions, a frame counter, and a timeline marking the critical frame.
+
+Sidebar controls: search, sort (critical-frame PSNR, task, manifest order), the episode list, a
+camera selector, an optional `|GT − generated|` difference panel, and playback fps — a 33-frame
+window is only ~1 s at native 30 fps. PSNR and MSE for the selected episode are shown underneath.
 
 ## Expected dataset layout
 
@@ -47,51 +38,39 @@ metrics_summary.json                  # optional: [{id, task, edge, arm, full_ms
                                       #   crit_mse, crit_psnr}, ...]
 windows/<episode_id>/gt.mp4           # required
 windows/<episode_id>/generated.mp4    # required, same geometry and length as gt.mp4
-windows/<episode_id>/actions.json     # optional: [T, D] driving actions
-windows/<episode_id>/meta.json        # optional: per-window metadata
 ```
 
-Only the two mp4s are required. With no `windows_manifest.json` the window list is discovered by
-listing `windows/` one level deep, and per-window metadata is read from each `meta.json` as you
-open it. Videos may stack **N cameras vertically** — N is inferred from the frame aspect ratio,
-and the camera selector adapts. Black letterbox bars are trimmed automatically, identically for
-GT and generated.
+Only the two mp4s are required. With no `windows_manifest.json` the episode list is discovered by
+listing `windows/` one level deep. Videos may stack **N cameras vertically** — N is inferred from
+the frame aspect ratio and the camera selector adapts. Black letterbox bars are trimmed
+automatically, identically for both videos.
 
 ## Storage model
 
-Nothing is downloaded at build time, and no repo is ever pulled whole — important for datasets
-too large to fit on the Space.
+Nothing is downloaded at build time and no repo is ever pulled whole, so datasets far larger than
+the Space still work.
 
 - Loading a repo fetches only the manifest and metrics JSONs (a few hundred KB), or one directory
   listing when there is no manifest.
-- A window's mp4s, `actions.json` and `meta.json` are fetched **the first time that window is
-  opened**, never in bulk.
-- Each browser session gets its own scratch directory. At most `MAX_WINDOWS_ON_DISK` windows stay
-  resident; beyond that the least recently used are deleted. Decoded frames are capped at 2
-  windows in RAM and composed strips at 1.
-- The whole directory is deleted when the session ends. A janitor also reaps sessions idle past
-  `SESSION_TTL` and directories orphaned by an earlier process, so nothing accumulates if a tab
-  dies without a clean shutdown.
-
-Rerun recordings follow the same rule: built on first view of the tab, cached beside the
-composed mp4, and evicted with their window. Frames go into the recording as JPEG (quality 90) —
-a raw recording of one 3-camera window is ~16 MB against ~1.5 MB compressed, which is the
-difference between usable and not over a browser connection. The trade-off is that extreme zoom
-in the Rerun viewer shows JPEG artifacts; the **Frame stepper** tab renders from the raw decoded
-frames if you need a pixel-exact look.
-
-The sidebar shows live occupancy (`cached this session: n/N windows`).
+- An episode's mp4s are fetched the first time that episode is opened, never in bulk.
+- Each browser session gets its own scratch directory. At most `MAX_WINDOWS_ON_DISK` episodes stay
+  resident; beyond that the least recently used are evicted along with their rendered videos.
+  Decoded frames are capped at 2 episodes in RAM and composed strips at 1.
+- The directory is deleted when the session ends. A janitor also reaps sessions idle past
+  `SESSION_TTL` and directories orphaned by an earlier process.
 
 ## Configuration
 
 | Variable | Default | Purpose |
 |---|---|---|
-| `DATASET_REPO` | `OneWorld-AI/abc-critical-window-rollout` | Repo prefilled in the input box. |
 | `HF_TOKEN` | — | **Required for private datasets.** Set under *Settings → Variables and secrets*. |
-| `MAX_WINDOWS_ON_DISK` | `12` | Windows kept per session before LRU eviction. |
-| `MAX_DISCOVER` | `5000` | Cap on windows listed when a repo has no manifest. |
+| `MAX_WINDOWS_ON_DISK` | `12` | Episodes kept per session before LRU eviction. |
+| `MAX_DISCOVER` | `5000` | Cap on episodes listed when a repo has no manifest. |
 | `SESSION_TTL` | `3600` | Seconds of idleness before a session's storage is reclaimed. |
 
+Note: on a public Space the `HF_TOKEN` is used to read whatever repo a visitor types, so scope it
+to only the datasets you are willing to expose.
+
 ## Running locally
 
 ```bash