The main-process sample showed the UI thread spending 100% of its time
in TicketArena::wait from the painted frame's synchronous render: every
cache-missed playhead frame sync-rendered inline, and the seek-priority
ticket then stole worker capacity from the pre-render window while the
blocked tick loop could not feed it — a self-reinforcing loop that made
playback unusably choppy.
On a playback miss the viewer now shows the last displayed frame while
the pre-render window warms up/catches up (paused monitors and the very
first frame keep the synchronous path). Adds a gpui test driving real
playback that requires the window to supply playhead frames, and the
real-footage bench_playback example used for the measurements
(152 fps aggregate on 1080p H.264 at 480p preview, decode-bound).
- Audio tickets join the process backend: render_audio_batch wire
message, workers mix straight into shm slots (SLOT_FORMAT_AUDIO_F32),
ShmAudio payload with release semantics, crash isolation covers audio
renders; playback audio uses an async 4-chunk prefetch drained on the
UI tick (also fixes the sub-60fps chunk truncation bug); oversized
ranges and dispatcher outages fall back to in-process inline.
- Per-ticket slot formats: force_format is honored (exports request
F32 slots, dropping the BGRA8 round-trip and its 8-bit quantization);
segments grow on demand via worker-idle rebuild with generation
handoff; the scheduler filters over-capacity tickets.
- Adaptive defaults: 128-256MB/worker segment budgets drive slots per
worker, batch size follows workers/slots; bench_process example
measures throughput and adjacent-frame completion deltas
(e.g. 4 workers: 841 fps, 4.6ms mean delta).
Mike-Solar