The RE pass against lghub_agent.arm64 plus the G522 live probe resolved
the V2 wire format. Key corrections to the previous implementation:
1. 5-byte stride is [filter_type, freq_hi, freq_lo, gain_hi, gain_lo].
The initial RE interpretation of [freq_hi, freq_lo, gain, q_hi, q_lo]
was wrong — the 0x78 byte is a filter-type sentinel (peaking), not
the high byte of a frequency.
2. No header before the bands. G522's default "header" was actually
band 0: a high-pass filter at 20 Hz (filter_type=0x00, freq=0x0014).
Total is 10 bands (1 HP + 9 peaking at ISO octaves), not 9.
3. Frequency is raw Hz as BE u16 — no log/ERB/bin transform. 0x4E20
is exactly 20000 Hz.
4. Gain is signed BE int16 (not int8), scaled by step_db from
getEQInfos. ±120 maps to ±6 dB at 0.05 dB/LSB on the G522.
5. No Q on the wire — firmware-fixed per filter type.
get_advanced_eq_info is unchanged (13-byte V2 decode was already right).
Parser tuple shape is now (filter_type_byte, freq_hz, gain_db) across
both V0/V1 and V2 paths; V0/V1 synthesises filter_type=peaking so the
shape is uniform. Band labels display real Hz — "HP 20Hz", "50Hz",
"125Hz", ..., "20000Hz" on G522.
Stays read-only. Will enable write once we round-trip-test with known
raw bytes.
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