Implement host-computed biquad EQ coefficient generation and multi-fragment
bridge writes for the PRO X 2 LIGHTSPEED headset's 5-band parametric EQ.
The coefficient algorithm uses standard Audio EQ Cookbook peaking EQ formulas
with a simplified rescale normalization (max_b0 × 1.19 headroom). This is our
own implementation — not an exact replica of LGHUB's ~350-line per-band cascade
normalization — but it produces functionally correct results. The DSP
compensates via the rescale factor, and the EQ changes are audible and working
on real hardware.
Wire format verified against 38 LGHUB pcap writes:
- 4-byte LE section headers, LE uint16 coefficient words
- Mixed Q1.31/Q2.30 fixed-point with 24-bit precision
- Only b-coefficients divided by rescale; a-coefficients unchanged
- Two sections: 48kHz playback + 16kHz mic
- No trailing padding, no extra words between sections
Changes:
- base.py: Add flags parameter to write_centurion_cpl() for multi-fragment CPL
- device.py: Rewrite multi-fragment bridge send — proper CPL fragmentation with
fragment 0 carrying bridge prefix/hdr and continuations carrying raw sub_msg,
all fragments sent back-to-back without intermediate ACKs
- hidpp20.py: Replace placeholder coefficient code with full biquad math,
mixed Q-format quantization, rescale normalization, and dual-section output
- settings_templates.py: Persist EQ to slot 0x80 after writing to slot 0x00
so settings survive power cycle
- tests: Update expected SetEQParameters payloads for new coefficient format
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