Denny Ma 7fb31b8648 feat(dab): share single EtiDecoder across all clients on same multiplex ... Previously each WebSocket client tuning to a DAB multiplex spawned its own EtiDecoder (OFDM demodulator). With 5 concurrent clients, 5 identical demodulators competed for CPU (~52-55% on a Pi 5), causing OFDM lock-loss (coarse time shift ~130,000) and audible breakup for all listeners. Fix: introduce DabDecoderManager (singleton) that maintains one SharedDabDecoder per (sdr_id, center_freq) pair, reference-counted by client connects/disconnects. Each client gets an independent pycsdr.Buffer reader into the shared ETI output (same fan-out mechanism as SpectrumThread in owrx/fft.py). Per-client DablinModule and MetaForwarder are retained so service selection and programme metadata remain per-client. Results measured on Raspberry Pi 5 with 4 concurrent clients: - CPU: ~52-55% → ~35% - Coarse time shift: ~130,000 (losing lock) → 1-8 (solid lock) - Lock lost events: frequent → zero - Programme list in browser: unaffected Adds docs/shared-dab-decoder.md explaining the problem, architecture, and known limitations (service-switch race when last client changes service). Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>		2026-03-15 18:18:05 +11:00
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shared-dab-decoder.md	feat(dab): share single EtiDecoder across all clients on same multiplex	2026-03-15 18:18:05 +11:00