Signal Lab  ·  Scene 03  ·  Geometry only, no entropy coder

Quadtree/Progressive.

A square grayscale frame gets cut where it is busy and left whole where it is flat. Down the pipe travels almost nothing: one signed byte of difference from the parent's colour, plus a single split bit. The decoder never receives a coordinate. It runs the same breadth-first queue as the encoder, so it already knows which rectangle the next byte belongs to.

Source128 × 128
Nodes—
Max depth—
0 / 0
24
01
Encoder

Breadth-first walk. A node splits when the worst pixel inside it strays further than the threshold from the node's mean.

current parent settled leaves
Index—
Depth—
Rect x, y, w, h—
Avg—
Parent avg—
Diff sent—
Split—
02
Transport

Nine bits per node. Nothing else is on the wire.

Sent0 B
Raw frame16,384 B
0raw size
—compression
03
Decoder

Starts at flat mid-grey. Rebuilds every rectangle from its own mirrored queue, then paints parent + diff.

Tree level— / —
Nodes decoded0
Queue pending0
04
Tree

Each row is one depth; a node's children sit within its span.

current + ancestors leaf edge not sent yet