Thumbnails stay on by default. --no-thumbnails skips building the preview sprite, so the server does no extra work and the rest of the player still works. The frontend already shows no preview when the sprite is unavailable.
Builds on the existing live seek/play/volume. Adds a polished, responsive control bar with play/pause, +/-10s skip, a played-progress fill, and a YouTube-style hover thumbnail preview on the seek bar. Thumbnails come from a small lazy /scrub endpoint that builds an in-memory sprite once per video with a single ffmpeg pass (no disk cache); easy to point at the static compiler's sprite instead.
The binary protocol re-sent the full grid every frame. This adds an opt-in
per-frame codec that picks the smallest of three encodings and tags it in a
1-byte header, without changing the rendered output:
0 RAW framebuffer as-is (legacy)
1 ZLIB zlib(framebuffer)
2 DELTA only the cells changed since the previous frame, patched on top
Clients opt in via /ws?codec=adaptive; omitting it yields the original protocol
byte-for-byte, so existing clients are unaffected. A keyframe is forced
periodically for resync. codec.js is shared by the browser and the Node test,
so the shipped decode path is the tested one.
Optional --quality {lossless,high,balanced,low} enables lossy temporal delta
(conditional replenishment): a colour cell is only re-sent once it drifts past a
tolerance from what the viewer already sees; the character plane stays exact.
Default lossless = bit-exact.
Measured wire savings (mode 5, 200x80): static screen 0.3% of legacy (~375x),
pixel mode 11.6%, high-motion 63% (never worse). Encoder tuned (zlib level 3,
smart candidate selection) to stay well under the frame budget.
Verified bit-exact two independent ways: Python->Node vectors and a live
adaptive-vs-legacy WebSocket diff. (A fuller mutation + Autobahn conformance
harness exists on request.)
