Add sliding-frequency audio receiver tuning

firmware/baseband/spectrum_collector.hpp

@@ -29,6 +29,7 @@
 #include "complex.hpp"
 
 #include "block_decimator.hpp"
+#include "dsp_decimate.hpp"
 
 #include <cstdint>
 #include <array>
@@ -40,8 +41,18 @@ class SpectrumCollector {
     void on_message(const Message* const message);
 
     void set_decimation_factor(const size_t decimation_factor);
+    void set_channel_filter_offset(const int32_t offset) {
+        channel_filter_offset = offset;
+    }
 
-    void feed(
+    bool feed(
+        const buffer_c16_t& channel,
+        const int32_t filter_low_frequency,
+        const int32_t filter_high_frequency,
+        const int32_t filter_transition);
+
+    void start_filtered_capture(const size_t decimation_factor);
+    bool feed_filtered(
         const buffer_c16_t& channel,
         const int32_t filter_low_frequency,
         const int32_t filter_high_frequency,
@@ -55,10 +66,19 @@ class SpectrumCollector {
     volatile bool channel_spectrum_request_update{false};
     bool streaming{false};
     std::array<std::complex<float>, 256> channel_spectrum{};
+    std::array<complex16_t, 1024> filtered_capture_{};
+    std::array<complex16_t, 512> filtered_stage_0_{};
+    std::array<complex16_t, 256> filtered_stage_1_{};
+    dsp::decimate::FIRC16xR16x63HalfbandDecim2 filtered_decim_0_{};
+    dsp::decimate::FIRC16xR16x63HalfbandDecim2 filtered_decim_1_{};
+    size_t filtered_capture_count_{0};
+    size_t filtered_capture_decimation_{1};
+    bool filtered_capture_ready_{false};
     uint32_t channel_spectrum_sampling_rate{0};
     int32_t channel_filter_low_frequency{0};
     int32_t channel_filter_high_frequency{0};
     int32_t channel_filter_transition{0};
+    int32_t channel_filter_offset{0};
 
     void post_message(const buffer_c16_t& data);