Fix SEL5 decoder Goertzel offset bank never being fed samples - #805
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Fix SEL5 decoder Goertzel offset bank never being fed samples#805MarkRose wants to merge 1 commit into
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The software SEL5 selcall decoder runs two Goertzel filter banks per tone: a main bank aligned to the detection block boundary and a half-block-offset bank meant to catch tones that straddle a block boundary. writeSamples() only fed samples into the main bank (row_out[k]); the offset bank (row_out[k+20]) never had its v2/v3 recursion updated, so it always evaluated to a zero energy result. Because both banks write into the same row_energy[k] slot, every time the offset bank's sample counter reached zero it clobbered the valid energy computed by the main bank with 0.0, blanking out roughly half of each detection window. This made findMaxIndex() intermittently miss real tones, causing the active_timer streak in Sel5PostProcess() to reset and selcall sequences to be dropped or misdetected. Fixed by feeding both the main and offset Goertzel states on every sample, using a small shared helper (feedGoertzel) so the per-sample recursive-filter update logic isn't duplicated between the two banks. Co-Authored-By: Claude Opus 4.8 <[email protected]>
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The software SEL5 selcall decoder runs two Goertzel filter banks per
tone: a main bank aligned to the detection block boundary and a
half-block-offset bank meant to catch tones that straddle a block
boundary. writeSamples() only fed samples into the main bank
(row_out[k]); the offset bank (row_out[k+20]) never had its v2/v3
recursion updated, so it always evaluated to a zero energy result.
Because both banks write into the same row_energy[k] slot, every time
the offset bank's sample counter reached zero it clobbered the valid
energy computed by the main bank with 0.0, blanking out roughly half
of each detection window. This made findMaxIndex() intermittently miss
real tones, causing the active_timer streak in Sel5PostProcess() to
reset and selcall sequences to be dropped or misdetected.
Fixed by feeding both the main and offset Goertzel states on every
sample, using a small shared helper (feedGoertzel) so the per-sample
recursive-filter update logic isn't duplicated between the two banks.
Co-Authored-By: Claude Opus 4.8 [email protected]
This PR also adds a unit test (
SwSel5DecoderTest.cpp). It is auto-discovered and executed by the CTest suite proposed in #762 once that is merged; without that suite present the test file is inert and does not affect the build.