Files
LEDMatrix/docs
ChuckandClaude Opus 5 7b4b07e313 perf(scroll): pace frames to the panel, not to a fixed sleep
Scrolling ran at 44-46 fps on a 2x128x64 chain and 14-17% of frames took
41-53ms, which reads as judder. Four independent causes, each measured on
the hardware; details and the diagnostic recipe are in
docs/SCROLL_PERFORMANCE.md.

The high-FPS loop slept a flat 8ms after every render. display() has
already blocked on the panel's vsync by then, so that sleep was added to a
wait that had happened: ~4ms of render plus 8ms put each iteration at ~12ms
against a 10ms refresh grid, so every swap missed a refresh and the loop
settled at 50fps while asking for 125 -- with no headroom, so a further
14% of frames slipped again. It now sleeps only the remainder, with a 1ms
floor so plugin threads still get the GIL.

ScrollHelper stepped position on a wall clock at 1/scroll_delay steps per
second. Plugins set scroll_delay to the frame period, so that comparison
sat exactly on its own threshold: a frame arriving a hair early moved zero
pixels and rendered an identical frame, dirty-tracking skipped the swap, it
returned in ~2ms, and the beat repeated. No scroll_delay value tunes that
out -- a shorter delay trades stalled frames for periodic double-steps.
Both modes now accumulate elapsed time at the same configured speed, so
position stays proportional to real time.

Sub-pixel blending goes back to off by default. It renders a half-step by
mixing two adjacent columns, which on a coarse panel showing pixel-font
text alternates crisp and smeared frames and reads as shimmer -- visibly
worse than integer stepping on the hardware. Vegas mode still opts in.

disk_cache uses orjson when importable, falling back to the stdlib. Encoding
a ~1MB record drops from 14.8ms to 5.4ms end-to-end, and that work holds the
GIL while a marquee is on screen. display_manager also checksummed the whole
framebuffer twice per frame (dirty tracking, then the preview snapshot); the
snapshot now takes the checksum the caller already computed.

New src/common/scroll_config.py resolves scroll settings in one place. Five
ticker plugins each hand-rolled this and disagreed: odds-ticker ranked the
deprecated scroll_pixels_per_second above the documented scroll_speed/delay
pair, and because that key carries a schema default the documented settings
were dead for every user (ChuckBuilds/ledmatrix-plugins#408), while
ledmatrix-leaderboard read the same key only as a fallback. The resolver also
warns when a speed will not advance a whole number of pixels per refresh,
which is the property that actually determines whether a scroll looks smooth.

scripts/build_rgbmatrix_nogil.sh rebuilds the rgbmatrix binding so it
releases the GIL. Upstream declares SwapOnVSync without nogil, unlike
SetPixel/Clear/Fill beside it, so the render thread held the GIL for the
whole vsync wait and starved background threads into long uninterruptible
bursts. The script patches, builds and self-verifies into a scratch tree;
--install backs up the original and rolls back if the service does not come
back healthy.

Measured after: 100 fps locked, no stalls observed, render thread down from
51% to 19% of one core.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
2026-09-03 17:45:45 -04:00
..
2025-12-27 14:15:49 -05:00
2025-12-27 14:15:49 -05:00

LEDMatrix Documentation

This directory contains guides, references, and architectural notes for the LEDMatrix project. If you are setting up a Pi for the first time, start with the project root README — it covers hardware, OS imaging, and the one-shot installer. The pages here go deeper.

I'm a new user

  1. GETTING_STARTED.md — first-time setup walkthrough
  2. WEB_INTERFACE_GUIDE.md — using the web UI
  3. PLUGIN_STORE_GUIDE.md — installing and managing plugins
  4. WIFI_NETWORK_SETUP.md — WiFi and AP-mode setup
  5. TROUBLESHOOTING.md — common issues and fixes
  6. SSH_UNAVAILABLE_AFTER_INSTALL.md — recovering SSH after install
  7. CONFIG_DEBUGGING.md — diagnosing config problems
  8. LOW_MEMORY_BOARDS.md — Pi Zero 2 W / 3B+ / 1GB Pi 4 memory limits

I want to write a plugin

Start here:

  1. PLUGIN_DEVELOPMENT_GUIDE.md — end-to-end workflow
  2. PLUGIN_QUICK_REFERENCE.md — cheat sheet
  3. PLUGIN_API_REFERENCE.md — display, cache, and plugin-manager APIs
  4. PLUGIN_ERROR_HANDLING.md — error-handling patterns
  5. DEV_PREVIEW.md — preview plugins on your dev machine without a Pi
  6. EMULATOR_SETUP_GUIDE.md — running the matrix emulator

Going deeper:

Configuring plugins

Advanced features

Reference

Contributing to LEDMatrix itself

Archive

docs/archive/ holds older guides that have been superseded or describe features that have been removed. They are kept for historical context and git history but should not be relied on.

Contributing to the docs

  • Markdown only, professional tone, minimal emoji.
  • Prefer adding to an existing page over creating a new one. If you add a new page, link it from this index in the section it belongs to.
  • If a page becomes obsolete, move it to docs/archive/ rather than deleting it, so links don't rot.
  • Keep examples runnable — paths, commands, and config keys here should match what's actually in the repo.