Entry 52

In-engine streams: the title's intro, event 1's cutscenes and the Audio screen's movies, bit for bit

2026-09-23enginerenderaudiotest

Filescrates/piney-streamcrates/piney-game/src/stream.rscrates/piney-game/src/desktop.rscrates/piney-game/src/session.rscrates/piney-gs/src/assets.rstools/test_stream_rs.pydocs/engine/stream.md

The last thing the title and a new game skipped was the in-engine streams: cutscenes the engine itself plays from STREAM/*.BIN (ccRequestLoadStream), not PSS movies (49). A helper agent ported them as piney-stream, and I put them in the runtime. The reference is the stream page.

What a stream is

• Where they are called. Three callers:
  • the title's PlayOpeningStream (stream 0, the intro);
  • the scripts' stream op (ccEventStream: event 1 plays streams 2 and 106 before its first lines, at frame rates 2 and 1);
  • the desktop Audio screen's movies (SimplePlayStream, at rate 2, with every desktop task asleep).
• Holding the caller. The call plays the whole stream before it returns, so each caller is held meanwhile.
• Inside. A stream is a list of scenes. Each is a CCS-like file with per-frame records (objects, camera, lights, materials, notes and PCM).
• Sound. The stream owns SEWORDS channel 0 from ccPcmSound::Open to Close. Its PCM is 1,024-byte SPU2 blocks at 48 kHz.
• Skip. WaitEnd decides it from the file's flags: 0x80 never, 0x40 on START, anything else on cancel. On the title after the desktop has run (DESKTOP_FLG), cancel always skips.
• This disc. 35 streams play: 0-20, 47, 106-119 and 133. The rest live on the later volumes' discs.

In the runtime

• The player. stream::StreamPlayer wraps a stream for all three callers. As it starts it stops the voice and channel 0's input. It then queues each block of samples (Audio::stream_pcm, appended after the last) and closes the channel at the end or on a skip.
• The event VM. It polls busy(Wait::Stream) once a frame while the op waits. The bridge steps the stream there, as the game's event task runs it inside the call. The stream's frame replaces the setup's black, or the desktop's frame.
• Frame rate. frame_rate now sets the setup's frame rate.
• The overlay archive. The frames name the stream's own files, which are not in DATA.BIN. piney-gs Assets gained an overlay archive, looked up first. The window loop sets it from Mode::archive each frame, and changing it drops the file textures read so far.
• The title. It waits on stream 0 as on a movie. DESKTOP_FLG is kept across resets.

Checked

• The port against the game. The stream agent's test_stream_rs.py runs the game's code in eemu and writes a fixture, which piney-stream's Rust test compares:
  • the table and file lists of all 134 streams, in both languages;
  • 180 cases of the skip rule;
  • the draw list of streams 0, 106 and 2;
  • every frame of streams 0 (410) and 106 (397), and the first 60 of 2: every object drawn and its matrix, bit for bit, the camera to 5e-7 and the light matrix to 6e-8.
• The fixture. I regenerated it from the game's code in a clean worktree (104 s). It is byte-identical to the one committed.
• A bug the agent fixed. Only a scene read whole into memory gets a frameOffsetTbl. The port had given every scene one, so stream 2's note frames came out one too high.
• The runtime.
  • movies_play now goes on past OPENING into stream 0, which draws on more than 150 of its first 200 frames.
  • setup_lines_are_voiced plays event 1's streams 2 and 106 for 120 frames each, hears their sound in more than 100 of those frames, then skips them with cancel and goes on to the voiced lines.
  • The session and desktop tests skip the streams with cancel and START, as a player would. piney-game has 8 tests, all passing; the workspace is clippy and fmt clean.
• Shots. GPU shots show stream 0's title logo and stream 2 mid-scene.