Videos: game view recordings are limited range, colour in the stream

- How it is made: the GPU turns the picture into I420, limited range
  BT.709, and avcColour.ts writes the colour into the SPS too.
- Why: VLC 3 showed full-range recordings too dark, even with the
  range in the stream. Older recordings stay full range.
- Development: 2068 editor checks.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

Development.md

@@ -21,7 +21,7 @@ php tests/php/releases.test.php                               # the release stor
 php tests/php/files.test.php                                  # uploaded files in a folder per account (#344), the same way
 php tests/php/videos.test.php                                 # the video store, its queue and the worker (#402), with the
                                                               #   real ffmpeg: the CI image and feuerwerk-video have it
-node tools/seed-e2e.mjs && node tools/e2e.mjs                 # 2067 editor checks, screenshots in /tmp/gm-e2e-*.png
+node tools/seed-e2e.mjs && node tools/e2e.mjs                 # 2068 editor checks, screenshots in /tmp/gm-e2e-*.png
 GM_STEPS=20 node tools/e2e.mjs                                # or 1-12, or 6,20 — a subset while working on one step
 ./e2e.sh start [GM_STEPS]                                     # the same run detached, see below
 ./e2e.sh status                                               # live progress, or the last run's result

Videos.md

@@ -223,12 +223,18 @@ Two action nodes record what the game view shows, with what the master plays (#4
 How it is made: H.264 from Chrome's `VideoEncoder` (VP9 where there is no H.264), hardware where
 the computer has it, 10 Mbit/s at 1080p60, a keyframe every 2 s. The file is Matroska, written by
 the editor itself (`src/core/recording/matroska.ts`) in clusters as the frames come, with the
-frame rate and the colour (BT.709) in its head, so nothing has to guess them. The rules (size,
-codec level, which frames are taken, where the picture goes in a frame) are plain functions in
-`src/core/recording/recording.ts`, the browser's side is `src/viewport/GameRecorder.ts`, and
-`src/viewport/PictureReader.ts` reads the frames back through pixel buffers with a fence. The
-encoders, the sound and the file are `src/viewport/RecordingTake.ts`, which the editor recording
-below shares.
+frame rate and the colour (BT.709) in its head, so nothing has to guess them. The colour goes into
+the H.264 stream as well (`src/core/recording/avcColour.ts` writes it into the SPS of the
+encoder's `avcC`), for players that read only the stream, such as VLC. A game view recording is
+limited range like any video: the GPU turns the picture into I420, limited range BT.709, before it
+is read back, and the encoder gets the planes with that colour. Fed RGB, Chrome's encoder made
+full-range video, and VLC 3 showed that too dark and its colours off, even with the range in the
+stream. Game view recordings saved before 2026-10-13 are full range and stay so. A player that
+heeds the range shows them right. The rules (size, codec level, which frames are taken, where the
+picture goes in a frame) are plain functions in `src/core/recording/recording.ts`, the browser's
+side is `src/viewport/GameRecorder.ts`, and `src/viewport/PictureReader.ts` reads the frames
+back through pixel buffers with a fence. The encoders, the sound and the file are
+`src/viewport/RecordingTake.ts`, which the editor recording below shares.
 
 ## Recording the editor