Added an audio FFT view in Wideband FM receive

Tried speeding up fill_rectangle for clearing the waveform widget

firmware/baseband/proc_wfm_audio.cpp

@@ -22,8 +22,9 @@
 
 #include "proc_wfm_audio.hpp"
 
+#include "portapack_shared_memory.hpp"
 #include "audio_output.hpp"
-
+#include "dsp_fft.hpp"
 #include "event_m4.hpp"
 
 #include <cstdint>
@@ -63,7 +64,50 @@ void WidebandFMAudio::execute(const buffer_c8_t& buffer) {
 	 * -> 4th order CIC decimation by 2, gain of 1
 	 * -> 96kHz int16_t[64] */
 	auto audio_2fs = audio_dec_2.execute(audio_4fs, work_audio_buffer);
-
+	
+	// Input: 96kHz int16_t[64]
+	// audio_spectrum_decimator piles up 256 bytes before doing FFT computation
+	// This should send an AudioSpectrum every sample rate/buffer size/(256/64)/refresh scaler = 3072000/2048/4/8 = ~47 Hz
+	// 0~3: feed continuous audio
+	// 4~31: ignore, wrap at 31
+	if (!(refresh_timer & 0xF8)) {
+		for (size_t i = 0; i < 64; i++) {
+			complex_audio[i] = { (int16_t)(work_audio_buffer.p[i] / 32), (int16_t)0 };
+		}
+		audio_spectrum_decimator.feed(
+			complex_audio_buffer,
+			[this](const buffer_c16_t& data) {
+				this->post_message(data);
+			}
+		);
+	} else {
+		// Spread the FFT workload in time to avoid making the audio skip
+		// "8" comes from the log2() of the size of audio_spectrum: log2(256) = 8
+		if (fft_stage && (fft_stage <= 8)) {
+			fft_c_preswapped(audio_spectrum, fft_stage - 1, fft_stage);
+			fft_stage++;
+		} else if (fft_stage > 8) {
+			AudioSpectrum spectrum;
+			const size_t spectrum_end = spectrum.db.size();
+			for(size_t i=0; i<spectrum_end; i++) {
+				//const auto corrected_sample = spectrum_window_hamming_3(audio_spectrum, i);
+				const auto corrected_sample = audio_spectrum[i];
+				const auto mag2 = magnitude_squared(corrected_sample * (1.0f / 32768.0f));
+				const float db = mag2_to_dbv_norm(mag2);
+				constexpr float mag_scale = 5.0f;
+				const unsigned int v = (db * mag_scale) + 255.0f;
+				spectrum.db[i] = std::max(0U, std::min(255U, v));
+			}
+			fifo.in(spectrum);
+			fft_stage = 0;
+		}
+	}
+	
+	if (refresh_timer == 31)
+		refresh_timer = 0;
+	else
+		refresh_timer++;
+	
 	/* 96kHz int16_t[64]
 	 * -> FIR filter, <15kHz (0.156fs) pass, >19kHz (0.198fs) stop, gain of 1
 	 * -> 48kHz int16_t[32] */
@@ -74,6 +118,12 @@ void WidebandFMAudio::execute(const buffer_c8_t& buffer) {
 	
 }
 
+void WidebandFMAudio::post_message(const buffer_c16_t& data) {
+	// This is called when audio_spectrum_decimator is filled up to 256 samples
+	fft_swap(data, audio_spectrum);
+	fft_stage = 1;
+}
+
 void WidebandFMAudio::on_message(const Message* const message) {
 	switch(message->id) {
 	case Message::ID::UpdateSpectrum:
@@ -117,6 +167,9 @@ void WidebandFMAudio::configure(const WFMConfigureMessage& message) {
 	channel_spectrum.set_decimation_factor(1);
 
 	configured = true;
+	
+	AudioSpectrumConfigMessage config_message { &fifo };
+	shared_memory.application_queue.push(config_message);
 }
 
 void WidebandFMAudio::capture_config(const CaptureConfigMessage& message) {

firmware/baseband/proc_wfm_audio.hpp

@@ -27,8 +27,10 @@
 #include "baseband_thread.hpp"
 #include "rssi_thread.hpp"
 
+#include "dsp_types.hpp"
 #include "dsp_decimate.hpp"
 #include "dsp_demodulate.hpp"
+#include "block_decimator.hpp"
 
 #include "audio_output.hpp"
 #include "spectrum_collector.hpp"
@@ -56,6 +58,12 @@ private:
 		sizeof(dst) / sizeof(int16_t)
 	};
 
+	std::array<complex16_t, 64> complex_audio { };
+	const buffer_c16_t complex_audio_buffer {
+		complex_audio.data(),
+		complex_audio.size()
+	};
+	
 	dsp::decimate::FIRC8xR16x24FS4Decim4 decim_0 { };
 	dsp::decimate::FIRC16xR16x16Decim2 decim_1 { };
 	uint32_t channel_filter_pass_f = 0;
@@ -67,6 +75,14 @@ private:
 	dsp::decimate::FIR64AndDecimateBy2Real audio_filter { };
 
 	AudioOutput audio_output { };
+	
+	// For fs=96kHz FFT streaming
+	BlockDecimator<complex16_t, 256> audio_spectrum_decimator { 1 };
+	AudioSpectrum fifo_data[1 << AudioSpectrumConfigMessage::fifo_k] { };
+	AudioSpectrumFIFO fifo { fifo_data, AudioSpectrumConfigMessage::fifo_k };
+	std::array<std::complex<float>, 256> audio_spectrum { };
+	uint32_t refresh_timer { 0 };
+	uint32_t fft_stage { 0 };
 
 	SpectrumCollector channel_spectrum { };
 	size_t spectrum_interval_samples = 0;
@@ -75,6 +91,7 @@ private:
 	bool configured { false };
 	void configure(const WFMConfigureMessage& message);
 	void capture_config(const CaptureConfigMessage& message);
+	void post_message(const buffer_c16_t& data);
 };
 
 #endif/*__PROC_WFM_AUDIO_H__*/

firmware/baseband/spectrum_collector.cpp

@@ -132,7 +132,7 @@ void SpectrumCollector::update() {
 	// Called from idle thread (after EVT_MASK_SPECTRUM is flagged)
 	if( streaming && channel_spectrum_request_update ) {
 		/* Decimated buffer is full. Compute spectrum. */
-		fft_c_preswapped(channel_spectrum);
+		fft_c_preswapped(channel_spectrum, 0, 8);
 
 		ChannelSpectrum spectrum;
 		spectrum.sampling_rate = channel_spectrum_sampling_rate;