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ew8bakandClaude Opus 4.8
be684545c8
Replaced linear interpolation upsampling (192k→device-rate) with a polyphase FIR interpolator ×L. Prototype: windowed-sinc lowpass (Blackman, ~-58 dB sidelobes), TAPS*L long, cutoff TX_FIR_CUT=40k, normalized to unity per-phase DC gain (loudness unchanged). Images at multiples of 192k are now suppressed ~-58 dB instead of only sinc², cleaning up the uplink spectrum. BuildTxResampler designs coefficients per FTxRatio in StartTX; FTxDlI/Q delay line persists across SendDUCIQ calls, reset on StartTX/ClearDUCIQQueue. Removed FTxPrevI/Q. Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>